Sunday, December 14, 2014

2014 Geology Posts That Never Quite Made It

A Lustrous Pearl for an Illustrious New Year; William Smith's Map That Changed the World; The Longitude Problem; Plaster of Paris Meets the Father of Comparative Anatomy; The Seine's Epic Journey to the Sea; Blue Sky, Green Water and Red Rocks on the Stove Pipe Trail; Born to Reproduce; The Oldest Cut Granite Building in America; The Granite Railway; and The Bridge that Spans Two Geologic Eras    

Every blogger knows the challenge. What shall I blog about next? What photos should I use? By the time the end of the year rolls around, there are always a few posts and photos that never quite made it. And so, with this final post of the year, here are a few from here and there, all from 2014. Please visit the same for 2013 here and 2012 here.

A Lustrous Pearl for an Illustrious New Year

My wife and I ushered in the New Year with our traditional early dinner at a wonderful local restaurant. To our surprise, one of the saltwater oysters in her appetizer contained an opaque white, natural pearl - a one-in-a-million chance. 

Pearls begin as foreign bodies within the mantle of a mollusk. The bivalve’s response is to secrete layer after layer of nacre (NAY-ker), a hard crystalline substance around the irritant for protection. The result is a pearl, which is similar in finish to the shiny inside of oysters and mussels, known as mother of pearl and can take 5 to 20 years to form (1 to 6 years for freshwater pearls). Light passing through the nacreous substance is reflected and refracted, which gives the pearl its luster and iridescence. This is because the thickness of the platelets of aragonite - a form of calcium carbonate (the other being calcite) - is close to the wavelength of visible light. Unlike gemstones that are cut and polished to bring out their beauty, pearls require no such treatment. 

Finding a pearl is considered to be good luck, and looking back on this year, I would affirm that superstition. 

William Smith’s Map That Changed the World

"Sing, cockle-shells and oyster-banks,
Sing, thunder-bolts and screw-stones,
To Father Smith we owe our thanks
For the history of a few stones."
Anniversary Dinner by A.C. Ramsey, 1854.

This eight by six-foot Delineation of the Strata of England and Wales with Part of Scotland is easily mistaken for a modern geologic map. Yet, it was created by William Smith in 1815 and was the first national-scale geologic map of any country covering 65,000 square miles. By far, it was the most accurate at its time and the basis for all others. Concealed behind stately green velvet curtains, it is on display in the foyer of the Geological Society of London’s Burlington House in Piccadilly alongside a bust of William. The Society is not to keen on allowing photographs of their geological masterpiece, so choose your moment carefully.

William Smith was born in 1769 in the hamlet of Churchill in Oxfordshire, the orphaned son of the village blacksmith. Raised by his uncle and with only a rudimentary education, he quickly learned the surveyor trade as an assistant. Fortuitously, he applied his skills with the Somersetshire Coal Canal Company, at which time he observed that rock layers within the canals were arranged in a predictable pattern and could always be found in the same relative positions. He also noted that each stratum was identifiable by the fossils that it contained and that the same succession of fossil groups from older to younger rocks could be found across the countryside, even as the layers dipped, rose and fell. In time, his astute observations led him to the hypothesis of the Principle of Faunal Succession – a major geological concept in determining the relative ages of rocks and strata. 

Travelling throughout Britain, he observed exposures of the strata and meticulously sampled and catalogued their characteristics. First mapping vertically and then horizontally in color, his first sketch in 1801 led to the publication of the geological map of Britain. The timing was right. This was the dawn of the Industrial Revolution in England. Coal was king, and maps were needed. Yet, Smith's maps were plagiarized by the Geological Society of London, forcing him into bankruptcy and debtor’s prison. Destitute but not deterred after years of homelessness, Smith's bad fortune began to turn. 

Over a decade later, he was eventually accepted into and honored by the Geological Society of London for his contributions as “the Father of English Geology.” In 1831, he was conferred the first Wollaston Medal by the Society in recognition of his achievements to the new science - all without a formal education in geology! It’s their greatest honor, bestowed by the very institution that denied him membership because of his low social status. Later, he was awarded an honorary doctorate of letters from Trinity College in Ireland. This uneducated surveyor rubbed elbows with famous astronomers, naturalists, biologists and geologists. 

Simon Winchester in his book The Map That Changed the World summed up Smith's map as the work of a lonely genius. He states, "The task required patience, stoicism, the hide of an elephant, the strength of a thousand, and the stamina of an ox. It required a certain kind of vision, an uncanny ability to imagine a world possessed of an additional fourth dimension, a dimension that lurked beneath the purely visible surface phenomena of the length, breadth and height of the countryside, and, because it had never been seen, was ignored by all customary cartography. To see such a hidden dimension, to imagine and extrapolate it from the little evidence that could be found, required almost a magician's mind - as geologists who are good at this sort of thing know only too well today."

The brilliance of William Smith’s achievement is demonstrated by comparing the accuracy and detail of his maps with the ones used by the Geological Society today and the rest of the world. His creation heralded the beginning of a new science and anointed him as its founding father. As for Dr. William Smith, nothing but goodness, recognition and respect attended the final years of his life.

The Longitude Problem

This is a High Dynamic Range photograph

"The College will the whole world measure;
Which most impossible conclude,
And navigation make a pleasure
By finding out the longitude.
Every Tarpaulin shall then with ease
Sayle any ship to the Antipodes."
Anonymous (circa 1660) from the Ballad of Gresham College 

On a foggy night in 1707, British Admiral Sir Cloudesley Shovell’s celebrated naval career was brought to a tragic end along with the lives of nearly 2,000 sailors, when his warship and three others in the fleet were wrecked on the rocks of the Isles of Scilly, off Great Britain's southwest coast. It was one of the greatest disasters at sea in British history and one of countless shipwrecks befallen to seafaring nations throughout history. The main cause of the British tragedy was the navigators’ inability to accurately determine their position at sea - longitude in particular. In response, Parliament established the Longitude Prize in 1714. The reward was for a "practical and useful" method for the precise determination of a ship’s longitude. The winner would collect £20,000 or roughly 4 million dollars in today’s currency, if accurate within half a degree (30 nautical miles at the equator). It was a large sum to pay for a desperate nation.

Back in school, we learned that our planet is divided into an imaginary grid. Hula hoop lines of latitude or parallels encircle it horizontally, the largest at the equator, while vertical, equi-length, pole-to-pole lines of longitude or meridians mark locations east or west of the Prime Meridian or 0º longitude. Unlike the equator, the Prime's location is arbitrary and is a universally-accepted reference line whose location has varied historically (Until 1911, the French used a Paris meridian). As of 1851, it runs through the Royal Observatory at Greenwich, England, which is located on a majestic hill overlooking the Thames River, where the above photo was taken looking north. The line is actually slightly to the right, but 500 happy kids were busy straddling the line with one foot in each hemisphere. Used together, latitude and longitude provide every location on our earthly sphere with a global address, and when calculated, indicate one’s whereabouts on a map – an important feat at sea when land is out of sight. If you know where you are, then you know where you're going. Admiral Shovell would surely have agreed.

One’s latitude is relatively easy to determine. Since ancient times, it was known that a star will consistently reach the same highest point in the sky, which changes with the observer’s latitude. By “sighting” the angle (declination) of the sun at it highest point from the horizon during the day or say the North Star at night, one’s position can be calculated from a table simply by knowing the time of measurement. On the other hand, finding longitude hasn't been so easy. Without it, ships at sea would follow a line of known latitude east or west, turn toward their assumed destination, and then continue on another line of known latitude. This process extended the voyage by days or weeks with increased risk of scurvy, bad weather, lack of potable water, starvation and worse - shipwreck. Another option was dead reckoning by using a predetermined “fix” and advancing that position based upon one’s known speed over time. Navigators threw a long, knotted rope attached to a log overboard and counted the number of knots let out in a given interval to allow a distance and speed calculation (which by the way is where we get the nautical term for speed at sea). The process was subject to cumulative errors induced by wind, current and change of course.  

The longitude problem was viewed by astronomers as requiring a celestial calculation such as by viewing eclipses of Jupiter's moons or our own, which required extensive heavenly observations and complex charts - hence the observatory in Greenwich. Clockmakers, on the other hand, envisioned the problem as requiring a temporal calculation. As expected from such a large reward, there was a myriad of hair-brained solutions such as a fleet of globally-distributed anchored ships that fired position-signalling cannons as longitude locators.

Ultimately, it was John Harrison, a self-educated English carpenter and clockmaker, who, after over four decades of toil and experimentation, successfully invented a masterpiece of engineering. His H4 (earlier versions were H1 through H3) was a pendulum-less “sea clock” that was unaffected by movement and changes in temperature. At sea, a ship’s captain could, using Harrison’s marine chronometer, calculate longitude by comparing the time on his pocket watch to a constant clock at a predetermined location.  

Here's how the the concept worked. The Earth makes a complete rotation on its axis every day. If there are 24 hours in a day, one hour of rotation is equivalent to 15º of rotation (360º ÷ 24). Thus, there exists a relationship between time and longitude. If you set your watch to 12:00 noon (not temporal noon but astronomical noon when the sun is highest in the sky at its zenith) at say Greenwich time, and you observe the sun at 4:00 PM at another location, then you’re at longitude 60º W (4 hours x 15º/hour = 60º). Finding local time was relatively easy. The problem was how to determine the time at a distant reference point while onboard a rocking, swaying, storm-tossed deck - an impossible task back in Cloudesley’s day with pendulum-swinging clocks that required a stable surface for accuracy.

Harrison's H4, which basically looks like an over-sized pocket watch, achieved all that and more - pendulum-less, compact, portable, shipworthy and accurate. Harrison's many timepieces are on display at the Royal Observatory, and as for their inventor, he spent his final years tinkering and experimenting with many timekeeping innovations - a very wealthy man. 

Plaster of Paris Meets the Father of Comparative Anatomy

This is a High Dynamic Range photograph

Built of gleaming white travertine (a redepositional form of limestone), the Basilica of the Sacred Heart radically changed the profile of the once pastoral, hilltop village of Montmartre - located on the northern outskirts of Paris and now an integral part of the city. Beginning in 1875, its 39-year construction was no easy task, since its foundation was literally riddled with subterranean gypsum quarries. 

Gypsum- an evaporite mineral formed by dehydration in an arid environment - is used in the manufacture of Plaster of Paris by heating it and then reapplying water to get it to harden. It has been excavated from beneath Montmartre from antiquity through the 19th century. Amongst its many decorative and artistic uses, it serves as an effective natural fire retardant on wooden structures, akin to our modern plaster board. After the Great Fire of London in 1666, its use was decreed by French King Louis XIV and literally saved Paris from the destructive fires that ravaged all major European capitals. 

The gypsum of Montmartre and the limestone of northern France formed within the Paris Basin. It began as an epeiric (shallow inland) sea on the northeastern fringe of Laurentia (the cratonic core of ancestral North America) some 200 million years ago. When the supercontinent of Pangaea fragmented apart beginning in the Late Triassic, the basin (and the new continent of western Europe) was tectonically transported to the Eastern Hemisphere on the Eurasian plate across an ever widening Atlantic Ocean. Once part of northern France, the basin’s sedimentary rocks of limestone and gypsum were deposited some 45 million years ago during the Lutetian Period of the Eocene. 

Outspoken critics of the Sacre Cour project - not only because of its exotic architecture but its exotic ideology - feared a seismic outcome related to its enormous weight. The architect, who had been commissioned to build his design, thought an immense platform of concrete four meters thick would stabilize the structure over the quarries. Instead, 80 stone pilings were laid down through the lime and clay and deeper through the voids of the quarries until bedrock was struck over 30 meters down. In effect, the foundation of Sacre Cour rests upon stilts like a dock on pilings over water. If an earthquake was to strike Montmartre, after the dust settled some Parisians thought the edifice would remain intact as if floating in air. 

When you visit Paris or on Google Earth, you can catch a glimpse of the entrance to one the quarries beneath the basilica fenced off on the northern end of rue Ronsard. It was in these very gypsum quarries that the famous French naturalist and zoologist Georges Cuvier excavated Eocene mammalian fossils from the strata in the 1790’s. His investigations led him to the inescapable conclusion that fossils were the remains of animals long-extinct. A lifelong Protestant, he believed that periodic catastrophies had befallen the planet and its lifeforms. That implied God had allowed some of his creations to vanish, a rather blasphemous conclusion against the tenets of the English church and one of the foundations of modern paleontology. Cuvier's contributions and uncanny ability to reconstruct lifeforms from their fragmentary remains led to his appellation as the “Founder of Comparative Anatomy.”

The Seine's Epic Journey to the Sea

Four large rivers water France – the Loire, the Seine, the Rhine and the Rhone – linked by a system of interconnecting canals. The second longest is the Seine (pronounced SEN), which begins a 776 kilometer (482 mile) journey to the sea from a modest cluster of springs called the Source de Seine northwest of Dijon. This is the Cote d’Or, literally “golden slope” that arguably produces the best wines (and mustards) in the world. It’s the right combination of climate, soil, and of course, clean water. 

The Seine flows through a thousand tiny hamlets, fields and woodlands, and halfway to the sea, right through the middle of Paris. It divides the city into its two famous banks - the conservative Left Bank or Rive Gauche and the radical Right Bank or Rive Droite. The Seine is the heart and soul of Paris, where the Parissi tribe first settled and where Romans took residence in their conquest of Gaul in 52 BC. 

The Seine flows through an enormous geological depression flanked by huge escarpments that began to flood when it was part of an intricate network of inland seas when the Atlantic Ocean was just beginning to open. The supercontinent of Pangaea’s fragmentation sent the Paris Basin adrift on the Eurasian Plate across the Atlantic Ocean, along with a network of interconnecting basins in western Europe. Good thing for France. The River Seine is actually a recent waterform within the ancient trough, having originated when the Pleistocene ice sheet and enumerable alpine glaciers sent their waters to the sea from the highlands that encompass the basin. 

Twenty-six tributaries later, the estuarine Seine discharges into the ocean, more precisely the English Channel, between the twinports of Honfleur and Havre, seen above through the clouds on my return flight from Paris to Boston.

Blue Skies, Green Water and Red Rocks on the Stove Pipe Trail

“The landscape everywhere, away from the river, is rock – cliffs of rock; tables of rock; 
plateaus of rock; terraces of rock; crags of rock – ten thousand strangely carved forms."
John Wesley Powell, 1875

Originating in the Wind River Mountains of Wyoming and skirting the northwest corner of Colorado, the Green River flourishes in Utah in all its glory. It's a 730-mile long, chief tributary of the Colorado River before reaching their confluence at the southern terminus of the Island in the Sky. In northeast Utah, the Green carves its channel over and through fluvial and marine rocks of Cretaceous age - grayish remnants of a vast inland sea that connected then-warm Arctic waters with those of the Gulf of Mexico, yet to form. In southeast Utah, things change dramatically, as the river downcuts through rocks of Jurassic, Triassic, Permian and Pennsylvanian origins.

This is Canyonlands, where John Wesley Powell in 1869 surveyed, mapped, described and named the landforms on the first of two expeditions to the region. First, through curvy Labyrinth Canyon and then more linear Stillwater Canyon, both appropriately named, the Green River slices its way back in time through confining cliffs of the Jurassic Glen Canyon Group and underlying erodible slopes and ledges of Triassic Chinle and Moenkopi Formations. The strata of these two geologic periods of the Mesozoic tell a tale of widespread Jurassic aridity in western Pangaea and distant Triassic mountain ranges draining across vast floodplains and river systems to the sea.

Our journey down the Green River - under the leadership of famous geologist Wayne Ranney and the supreme navigational skills of Walker Mackay and his family-run Colorado River and Trail Expeditions or CRATE - rafted us into camp at the foot of the Stove Pipe Trail in Stillwater Canyon, about seven miles upriver from the confluence. 

To work up an appetite for dinner, we ascended over 1,000 feet through a series of switchbacks and a palette of colors derived from cherty, chalky limestones and dolomites, pale-red sandstones, blue-gray siltstones and thin beds of evaporites of the Elephant Canyon Formation. At the top, where the photo was taken, the white to pale-reddish brown and salmon-colored Cedar Mesa Sandstone comes into view, forming the cliffs and ledges that hold it all up. These Permian strata are derived from the Ancestral Rocky Mountains or, more appropriately, the southwest range of the Uncompahgre Highlands that began their ascent in Pennsylvanian time. As they rose, the inexorable forces of erosion tore them down. Here too was an inland sea represented by the Uncompahgre's flexural trough that persisted with intermittent communications with the ocean and whose dimensions vacillated with the whim of South Polar glaciation an astounding 33 times. To see the strata within the trough, we had to wait for the following day in order to travel further down the Green. 

Both long gone, the highlands and basin left their signature deposits from Colorado to Utah. Uplift and erosion of the Colorado Plateau have put the finishing touches on the landscape. What's left is a rainbow feast for the eyes!

Born to Reproduce

On a glorious Spring afternoon outside of Boston, I exited the train station and began the short walk home. A bright colored object on the ground caught my eye, and, glancing down, I spotted this splendid Cecropia Silkmoth (si-KROH-pee-uh) on the pavement. A little worse for wear, I photographed it with my cellphone. I recognized the creature, having remembered a pinned specimen from sixth grade biology class so long ago. 

The cecropia is North America’s largest moth and are abundant east of the Rockies, although this specimen is the first I’ve seen outside of class. Females achieve a wingspan of seven inches! The larvae are mostly found largely on maple trees, which squirrels fastidiously dine on. I suspect this is a male, based on the more resplendent morphology of its antennae, having evolved as such for one specific purpose. 

Born to reproduce, nocturnally-active males lack functional mouthparts and a digestive system, and therefore survive only a few weeks. Unable to resist, males fly miles following the scent plume of wind-born female pheromones, guided by their antennae. Using an adaptive process called chemical mimicry, bolas spiders copy the pheromones produced by cecropia females, in order to lure males into their next meal. Predators and their prey exist up and down the food chain at virtually every level.

Architectural Geology of Boston – the Oldest Cut Granite Building in America

"In the love of truth, and the spirit of Jesus Christ,
We unite for the worship of god and the service of man."
King's Chapel Covenant

King’s Chapel in Boston was designed by Peter Harrision of Rhode Island and built in 1754 on the site of a smaller wooden Anglican church, itself built in 1688. It was situated on the public burying ground, because no resident would sell land for a non-Calvinist church. The stone church was constructed around the wooden church, so that the parishioners could continue to practice their faith, and was later disassembled and removed through the windows of the new church. 

The edifice is a classic example of American Georgian architecture – eponymous for the first three British monarchs of the House of Hanover, all named George in the early 18th and early 19th centuries. Its salient architectural features include a tall, boxy portico surrounded by 12 painted Ionic columns made of wood. The cornice has decorative mouldings and is topped off with a spindled-balustrade that terminates in a flat-roofed tower with four louvered, arched windows. The planned steeple was never built, which gives the church its distinctive "unfinished" look. Directly behind, the chapel has a characteristically four-sided, hipped roof. The Georgian style was big in eastern America, that is until King George III and the American Revolution turned the aesthetic sentiment elsewhere.

King’s Chapel was originally planned to be of English sandstone but was built with native Quincy Granite. It's the oldest, still-standing granite building in Boston but not the first to utilize granite, having been incorporated into many early foundations and associated structural elements. The blocks of granite demonstrate a patchwork color mix with pockmarked surfaces on the exposed “seam-faces.” 

The granite's appearance is reflective of the mode of quarrying from boulders scattered about rather than from excavated bedrock. The process involved heating and splitting the granite with heavy iron balls, followed by hammering, chiseling and shaping into stackable units. The "quarry" locale was Quincy (pronounced KWIN-zee), about 10 miles south of Boston. The town is officially called the “City of Presidents” after John Adams and John Quincy Adams, but its nickname is the Granite City. A hundred years later, the use of famous Quincy Granite in construction would become commonplace in Boston, and quarrying the bedrock would become a major commercial enterprise there.

By the way, in the bowels of King's Chapel is a 200-year old crypt and in the tower is the largest and last bell made by Paul Revere. It's located on the famous Freedom Trail, the red brick line on the pavement in front of the chapel.

The Granite Railway

In the face of great opposition to his idea, architect and engineer Solomon Willard traipsed all across New England looking for the perfect stone. His plan, after several architectural modifications, was the construction of a 221-foot tall obelisk out of Quincy Granite - the Bunker Hill Monument - situated in Charlestown across the harbor from Boston. By comparison, the Washington Monument - built to commemorate George Washington - was completed in 1884 on the National Mall in Washington, DC, and is the world's tallest stone obelisk at 555 feet. Willard's edifice was built to commemorate the Battle of Bunker Hill, the first major conflict between the British Regulars and the Patriot forces of colonial militiamen in the Revolutionary War fought in 1775. Technically, the monument is not on Bunker Hill but on Breed’s Hill, where most of the fighting in the misnamed Battle of Bunker Hill actually took place.

In 1825, Willard recognized there was something special about the granite in the hills west of Quincy. It wasn’t its convenience, since the granite still had to be excavated - no easy or safe task back then. It wasn’t its proximity (although that helped), since a lot of varied terrain stood in the way of the granite’s final destination. And it wasn’t the granite’s massivity - not meaning lots of it (which there was) but referring to its consistent homogeneity for aesthetic purposes. 

It was from Quincy Granite’s unique mineral composition. The high percentage of alkali feldspar, as opposed to the plagioclase variety, affords the rock its dusty gray, greenish tint, aided by its variety of black quartz. Formed from the slow crystallization of magma some 450 million years ago when the micro-terrane of Avalon was in transit to Laurentia, the granite’s characteristic mineral of riebeckite, a brittle prismatic amphibole, allows the rock to achieve a high polish, in addition to its lack of micas. Quincy Granite was the rock that Willard sought - attractive, distinctive, stately, transports well, available, highly polishable and weather-resistant. 

However, a major obstacle in 1826 was getting multi-ton blocks out of the ground, down from the heights above Quincy and across 12 miles of swamp, forest and farms for construction. After considering an overland route, the solution of how to transport the blocks from the quarry to a dock on the Neponsett River was modeled after English railroads. The idea for the Granite Railway was conceived and became not the first public transportation railroad in the United States but the first purpose-built, commercial railroad. 

It ran only three miles with wagons pulled by horses, although steam locomotives had been in operation in England for two decades. Wooden and later granite rails on stone crossties were plated with iron. In 1830, a new section of railway called the Incline, seen above, was added to haul granite from the quarry, one of many above town. Wagons and horses moved up and down the 315 foot incline in an endless conveyor belt. From the docks, blocks were loaded on barges that traveled across Boston Harbor. Off-loaded onto ox-drawn carts, the cargo went up a hill at Charlestown for construction of the obelisk. The capstone was laid in 1842 at a project cost of $101,680. Interestingly, the monument underwent a 3.7 million dollar renovation in 2007 - the cost of 36 monuments!

The Incline remained in operation until the 1940’s with metal channels laid over the old granite rails and motor trucks pulled by a cable. In 1871, steam trains carried the granite directly to Boston from the quarries.

These days, the quarries have been filled in for safety purposes with 12 million tons of dirt from the Big Dig highway project in Boston. In years past, many young persons were injured or killed while swimming and cliff diving into the abandoned quarries that had filled with water. Ironically, the steep quarry walls are used today by organized groups of rock climbers to hone their skills. As for the Granite Railway, it's listed on the U.S. National Register of Historic Places, while the Bunker Hill Monument towers over Charlestown across the harbor from Boston proper. You could see it from the quarry, if it wasn’t for the city's tall buildings. The Bunker Hill Monument is managed by the National Park Service and is on Boston’s Freedom Trail. 

The Bridge that Spans Two Geologic Eras

Viewed from Upper Manhattan, the George Washington Bridge spans the Hudson River between New York and New Jersey. Its footings are secured in two geologic eras. Cross the bridge heading west, and you time-travel from the Late Proterozoic to the Paleozoic. During the Late Triassic, the supercontinent of Pangaea began its fragmentation and newly-evolving dinosaurs were trudging through the mudflats of the Jersey Meadowlands. That epic schism created the continents of our New World and the Atlantic Ocean within the void, while the North American and Eurasian tectonic plates continue to drift apart. 

During supercontinental breakup, aborted rift basins from the Canadian Maritimes to Georgia developed up and down the margin of North America. In northeastern New Jersey and southeastern New York, the Newark rift basin subsided and listrically tilted as molten mafic rocks injected through the depocenter’s sedimentary strata into black argillites of the Lockatung Formation. The prominent cliff seen above on the western bank of the Hudson represents the eroded edge of that angulated, tabular intrusive sheet – the famed Hudson River Palisades. Its obvious vertical jointing formed when the magma solidified, so spectacularly exposed by the carving of the Hudson Canyon during the last Ice Age. 

The Palisades was threatened by quarrying in the early 20th century, when J.P. Morgan, American financier, banker, philanthropist and art collector, purchased twelve miles of New Jersey shoreline. On the east side of the river in Washington Heights, John D. Rockefeller, American business magnate and philanthropist, acquired the land of Fort Tyron and the Cloisters, where this photo was taken. 

Thankfully, the natural beauty of the Palisades cliffs rising above the west bank of the Hudson has long been appreciated by generations of residents and visitors to the metropolitan area. But now, LG Electronics, a South Korean multinational electronics corporation, is planning to build an office tower that will rise high above the trees, and for the first time, violate the unspoiled ridgeline. Interested in preserving the Hudson River Palisades? Visit “Protect the Palisades” here.

That's all folks. Thanks for following my blog! Happy New Year!

Friday, November 28, 2014

Richard E. Byrd III’s National Champion Eastern Hophornbeam Tree

“There are trees, and then there are trees.”
Dick Byrd, 2014

My neighbor, Dick Byrd of Newton, Massachusetts, has a lot to be thankful for. One of his biggest joys is growing or should I say towering in his front yard. It’s a tree, but not just any tree. It’s an Eastern Hophornbeam, and it’s the National Champion – the largest of its species growing in the United States!

We all know that a champion is a person who has defeated or surpassed all of his/her rivals in a competition. It includes someone who fights or argues in support of another person, cause or belief. But what's a champion tree?

It will come as no surprise, that to qualify, a tree must be big. It must be the largest species according to a standard measuring formula, and it must be re-measured every 10 years in order to maintain its champion status. To be eligible, a tree must be native to or naturalized in the continental United States, including Alaska but not Hawaii.

American Forests is the oldest national nonprofit conservation organization in the United States. Their mission is to restore threatened forest ecosystems and inspire people to value and protect urban and wildland forests. Since 1940, their National Big Tree Program has been a testament to American Forests’ legacy of leadership in recognizing the beauty and critical ecosystem services provided by the country's biggest and oldest trees. More than 750 champions are crowned and documented in their biannual American Forests Champion Trees national register, located here.

For more than 70 years, the goal of the program has remained to preserve and promote the iconic stature of these living monarchs and educate people about the key role that these remarkable trees and forests play in sustaining a healthy environment.

Trees are ranked by total points based on the following formula: Circumference (in inches) + Height (in feet) + ¼ Crown Spread (in feet). The tree with the most total points is crowned national champion. The nomination deadlines are March and September 15th for the spring and fall registers, respectively. Dick's champion Hophornbeam has 210 points! I'll tell you how to measure your tree later in the post.

The Eastern or American Hophornbeam - Ostrya virginiania if you're trying to impress Dick - is a member of the birch family of trees. Also known as ironwood, hardhack (in New England) and leverwood, it's generally a small short-lived tree scattered in the understory of hardwood forests. The tree is generally a subordinate species or minor member of most forest communities, when present. That's another unique aspect of Dick's champion - its unusually large size. Perhaps thriving in "the open" and Dick's nurturing nature has facilitated its large growth. 

The Eastern Hophornbeam is a rugged, shade-tolerant tree with an oval or round canopy that grows to 50 feet in height. Dick's champion tops out at 66! It's found throughout the eastern United States and within the mountains of Mexico, south to El Salvador and Honduras. Over this large native range, it thrives in a diversity of climatic conditions and soils. Its small nutlets, which ripen in summer and fall, are used by birds and mammals during the winter. 

It's often grown as an ornamental plant and sometimes used as a street tree. Because of its hardness, it has been used to make tool handles for mallets and posts. It should not be confused with the hornbeam, which is also a member of the birch family. The bark of a hophornbeam has loose strips of reddish brown to gray, creating a rough "clawed" bark.

The hophornbeam's leaf is doubly-serrated with fine teeth at the margin and 2-4 inches long.

I asked Dick what he knew of the age of his champion, it being slow-growing and having achieved such a large size. His best guess was about 135 years based on the age of his house. Dick speaks with the knowledge and ecological pride that comes from his BS in Forestry that he received from the University of Maine, although he doesn't pursue that profession, other than avocationally.

Gazing up at the hophornbeam and shaking his head, Dick says that it has lost a good two-thirds of its crown, and that it wasn't registered until it lost the first third. "After losing the first third, no one would ever know that you have a champion. That's why I registered it. I looked up the previous champion - a tree in Michigan. The Commonwealth came to measure it near the end of 2008."

Dick continued, "These types of trees are often culled early for pulpwood." Given its age and the deteriorated condition of its trunk, he fears that its days are numbered. "One good nor'easter, and that's it!" He's thought of cutting it down but is obviously highly reluctant.

Even before I met Dick, I couldn't help but notice the tree as I jogged through the neighborhood. Maybe it was the signage that he proudly placed on the tree that caught my eye - one high and the other low. "Why the low signage?" I asked. "It's for the kids, and it's fun for everyone to read about it." Unfortunately, the bark that held the signs has rotted off, and they're now displayed on the logs.

I was grateful for Dick telling me the story of his Eastern Hophornbeam and seeing his arboreal pride. He walked me back to my car, and quite sincerely added, "It's nice to find somebody that appreciates a championship tree!" And that I did! I must admit that I sneaked back the next morning to catch the morning sun illuminating its still majestic crown.

1. Measure the distance around the trunk of the tree, in inches, at 4 ½ feet above ground level. This point is called the diameter breast height or dbh.
2. If the tree forks at or below 4 ½ feet, record the smallest trunk circumference below the lowest fork. Record the height at which the measurement was taken. Trees should be considered separate if the circumference measurement below the lowest fork places the measurement on the ground.
3. If the tree is on a slope, measure 4 ½ feet up the trunk on the high and low sides of the slope. The dbh is the average between both points. If the tree is on a steep slope, take the measurement at 4 ½ feet above the midpoint of the trunk.
4. If the tree is leaning, measure the circumference at 4 ½ feet along the axis of the trunk. Make sure the measurement is taken at a right (90 degree) angle to the trunk.

Measure the vertical distance, in feet, between the base of the trunk and the topmost twig. Height is accurately measured using a clinometer, laser, hypsometer, or other specialized tools.  If these tools are not available, height can be estimated using the following “stick method.”

1. Find a straight stick or ruler.
2. Hold the stick vertically at arm’s length, making sure that the length of the stick above your hand equals the distance from your hand to your eye.
3. Walk backward away from the tree. Stop when the stick above your hand is the same length as the tree.
4. Measure the distance from the tree to where you are standing. Record that measurement to the closest foot.

Two measurements of the crown spread are taken and recorded, in feet, at right angles to one another.
1. Measure the widest crown spread, which is the greatest distance between any two points along the tree’s drip line. The drip line is the area defined by the outermost circumference of the tree’s canopy where water drips to the ground.
2. Turn the axis of measurement 90 degrees and find the narrow crown spread.
3. Calculate the average of the two crown spread measurements using this formula: (wide spread + narrow spread)/2 = average crown spread.

Tuesday, October 28, 2014

A Visit to the Miocene Sea at Maryland’s Spectacular Calvert Cliffs: A Geologic and Paleontologic Overview

In “101 American Geo-Sites You’ve Gotta See,” author Albert B. Dickas listed Maryland's Calvert Cliffs as number 32. With curiosity piqued and the Cliffs renowned for their diverse and well-preserved fossiliferous assemblages - having attracted tourists and scientists as early as 1770 - I decided to visit the site in July. Only a 90 minute drive southeast of Washington, the Calvert Cliffs is a spectacular and scenic, almost continuous 50 km wavecut bluff along the western side of the Chesapeake Bay.

A geological contradiction to the Eastern Seaboard's otherwise flat Coastal Plain, the Cliffs rise in places to as much as 40 meters. They are cut into actively eroding, unconsolidated sandy, silty and clayey sediments of the lowermost portion of the Chesapeake Group. Throughout much of the Miocene, the region was the site of a shallow, inland arm of the temperate Atlantic Ocean during climatic cooling, uplift of the Atlantic Coastal Plain and eustatic changes in sea level. The stratal package preserves the best available record of middle Miocene marine and, less frequently, terrestrial life along the East Coast of North America.

Looking obliquely at Calvert Cliffs from the cuspate foreland at Flag Ponds, the undeformed beds of the Chesapeake Group can be seen to have a regional dip of less than one degree to the southeast (about 2m/km). That allows the exploration of progressively younger strata in a southward direction and vice versa. The strata is primarily Miocene with a coarse-channel, fluvial and tidal deposited overburden variably from the Pliocene and Pleistocene. Typical of bluffs adjacent to the bay, the beach and cliff-vegetation is small or non-existent. Notice the slump and collapse material at the base. Its presence at the toe is generally short-lived. The beach at Flag Ponds is very popular for sunning, swimming and strolling, but fossil collecting at the cliff-toes, which is a very productive locale, is prohibited and prevented by the presence of a large fence.

The recorded history of the Chesapeake region is as varied as the geology, which began with the Spanish. The cartographer Diego Gutierrez recorded the Chesapeake on a map, calling it “Bahia de Santa Maria.” The English arrived with John White in 1585 and again in 1608 with John Smith’s entry onto the Calvert Peninsula. His mission was to explore the Chesapeake region, find riches, and locate a navigable route to the Pacific, all the while making maps and claiming land for England. On John Smith’s 1606 map (below), the Calvert Cliffs were originally called “Rickard’s Cliffes”, after his mother’s family name. 

The first English settlement in Southern Maryland dates to somewhere between 1637 and 1642, although the county was actually organized in 1654. Established by Cecelius Calvert, the second Lord Baltimore, English gentry were the first settlers, followed by Puritans, Huguenots, Quakers, and Scots. In 1695, Calvert County was partitioned into St. Mary's, Charles, and Prince George's, and its boundaries became substantially what they are today. Statehood wasn’t granted to Maryland until 1788. The Revolutionary War, the War of 1812 and the Civil War waged in the region. In fact, the peninsula was the training site for Navy and Marine detachments, and the invasion of Normandy was simulated on the lower Cliffs of Calvert.

John Smith's 1606 map of the Chesapeack (correct spelling) Bay. Note the location of Rickards Cliffes (English spelling) emptying into the Virginia Sea (aka Atlantic Ocean). North is to the right. Maryland was granted statehood in 1788 with the region referred to as Virginia.

The Cliffs of Calvert reside on the broad, flat, seaward-sloping landform of the Coastal Plain of Maryland on the western shore of the Chesapeake Bay in Calvert and southernmost Anne Arundel Counties. Located on finger-like Calvert Peninsula, the Cliffs are on the higher western section of the Plain, while the lower section, known as the Eastern Shore (always capitalized), is a flat-lying tidal stream-dissected plain, generally less than 60 feet above sea level. 

Red arrow indicates the region of Calvert Cliffs on the Atlantic Coastal Plain of the eastern shore of the Calvert Peninsula within the Chesapeake Bay.
Modified from USGS map

Chesapeake Bay is an estuary - the largest of 130 in the United States - with a mix of freshwater from the Appalachians and brackish water from its tidal connection to the Atlantic Ocean. The Bay's central axis formed by the drowning of the ancestral Susquehanna River by the sea that flowed to the Atlantic from the north during the last glacial maximum of the Pleistocene Ice Age some 20,000 years ago - when the planet's water was bound up in ice and global seas were lower.

Multiple advances of the Laurentide Ice Sheet blanketed Canada and a large portion of northern United States during Quaternary glacial epochs. Its advance never reached the region of Chesapeake Bay, having extended to about 38 degrees latitude. Being in a contemporary interglacial period - the Holocene - global seas are higher, but not at the level during the deposition of the Chesapeake Group at Calvert Cliffs during the Miocene.  

During the time of deposition of the Calvert Cliffs, fluctuating seas drowned portions of southern Maryland. A shallow, protected basin of the Atlantic Ocean called the Salisbury Embayment was located in Virginia, Maryland, Delaware and southern New Jersey. It was one of many depocenters along the Eastern Seaboard, separated by adjoining highs or arches. The Salisbury Embayment structurally represents a westward extension of the Baltimore Canyon Trough that extends into the central Atlantic on the continent's shelf and slope.

Major Structural Features of the Atlantic Coastal Plain from New York to Florida
The embayments are depocenters - major sites of sediment accumulation. The Fall Line is the inner limit of deposits on the Coastal Plain at the Appalachian Piedmont Province. The Salisbury Embayment extends westward to the Fall Line.
Modified from Ward and Strickland, 1985.

The depositional history and relief of the Cliffs of Calvert are testimony to the elevated level of the seas in the Miocene. In addition, the Embayment resides on the “passive” margin of North America’s east coast, which is typified by subsidence and sedimentation rather than seismic faulting and volcanic activity found on the continent’s “active” west margin. The Embayment was and is in a constant dynamic state - passive but far from inactive. 

How did the passive margin and the Coastal Plain of Maryland form geologically? What is the sediment source of the depocenters? What fauna occupied the ecosystem of Calvert Cliffs? These questions can't be adequately addressed without gaining an appreciation for the geological evolution of North America's East Coast. Here's a brief synopsis.

The supercontinent of Rodinia fully assembled with the termination of the Grenville orogeny in the Late Proterozoic and brought the world's landmasses into unification. Rodinia's tectonic disassembly in the latest Proterozoic gave birth to the Panthalassic, Iapetus and Rheic Oceans, amongst others. Rodinia's fragmentation was followed by the supercontinent of Pangaea's reassembly from previously drifted continental fragments throughout the Paleozoic. 

A succession of orogenic events...
Using modern co-ordinates, the east coast of Laurentia (the ancestral, cratonic core of North America) experienced a succession of three major tectonic collisions during Pangaea's assembly – the Taconic (Ordovician-Silurian), Acadian (Devonian-Mississippian) and Alleghanian (Mississippian-Permian) orogenies. Each orogen built a chain of mountains that overprinted those of the previous event - closed intervening seas and added crust to the growing mass of the continent of North America. 

The Paleozoic Assembly of Pangaea
In the Early Devonian (400 Ma), following the Taconic orgeny, the Acadian collisional event has initiated mountain building on Laurentia's east coast with the closure of the Iapetus Ocean. The megacontinent of Gondwana, lying across the Rheic Ocean, is converging upon Laurentia towards its eventual subduction zone.
Modified from Ron Blakey and Colorado Plateau Geosystems. Inc.

A final orogeny assembles Pangaea...
The penultimate Alleghanian orogeny between Laurussia (Laurentia, Baltica and Eurasia) and the northwest Africa portion of Gondwana - the two largest megacontinental siblings of Rodinia's break-up - culminated with the late Paleozoic formation of Pangaea. That unification event constructed the Central Pangaean Mountains - a Himalayan-scale, elongate orogenic belt some 6,000 km in length within Pangaea at the site of continental convergence. Calvert Cliffs (red dot) had not yet evolved, but its deep Grenville basement was in place along with the orogen that would eventually blanket its coastal seascape with sediments from the highlands.

The Supercontinent of Pangaea
By the Late Pennsylvanian (300 Ma), the closure of the Rheic Ocean brought various microcontinents, magmatic arcs, and the northwest African and Amazonian aspect of Gondwana into an oblique transpressive collision with Laurussia (summarily Laurentia, Scandinavia and Eurasia). Convergence built the elongate Central Pangaean range composed of segments from South America and Mexico through North America and into Europe and Asia. The Chesapeake Bay, yet to form, is landlocked at the red dot.
Modified from Ron Blakey and Colorado Plateau Geosystems. Inc.

Supercontinental fragmentation...
Beginning in the Late Triassic, Pangaea’s break-up created a new ocean – the Atlantic – and fragmented the Pangaean range. As a result, the Appalachian chain remained along the passive eastern seaboard of the newly formed continent of North America from Newfoundland to Alabama, while severed portions of the range were sent adrift on rifted continental siblings. A supercontinental tectonic cycle is apparent between Grenville formation of Rodinia and its fragmentation and Alleghanian formation of Pangaea and its dissassembly.

The orogen's remnants form the Anti-Atlas Mountains in western Africa, the Caledonides in Greenland and northern Europe, the Variscan-Hercynian system in central Europe and central Asia, the Ouachita-Marathons in south-central North America, the Cordillera Oriental in Mexico, and the Venezuelan Andes in northwestern South America. As a result of Pangaea's fragmentation, the region of the future Calvert Cliffs (red dot) was finally positioned in proximity to the sea, awaiting the orogen to erode and Cenozoic eustasy to flood the landscape and deposit the Chesapeake Group during the Miocene.

The Continent of North America
The Atlantic Ocean began to form with the disassembly of Pangaea in the Late Triassic. In the Late Jurassic (150 Ma), the modern continents are drifting apart. The Appalachian Mountain range has begun to erode and shed its deposits on the developing Atlantic Coastal Plain (light blue). The Chesapeake Bay, yet to form, is located at the red dot.
Modified from Ron Blakey and Colorado Plateau Geosystems, Inc.

North America's new passive margin...
By the Cretaceous, the Appalachian highlands had eroded to a nearly flat peneplain, sending voluminous fluvial sediments to the continental margin and shelf in a seaward-thickening wedge. Under the weight and the effect of lithospheric cooling, the passive marginal shelf began to subside and angle seaward as global warming and rising seas drowned both the coast and cratonic core of North America. The Salisbury Embayment, along with others up and down the coast in a scalloped array, was created by the tilting and reactivation of normal faults that extended westward to the Appalachian foothills. Initially, the regional dip was to the northeast, but Neogene uplift left the Coastal Plain's beds dipping to the southeast.

North America in the Late Cretaceous (89 Ma)
The entire shallow, subsiding passive margin of North America's east coast (light blue), along with the depocenters of the Salisbury Embayment (ellipse), were drowned by global high seas beginning in the Late Cretaceous. Notice that the cratonic core of Laurentia has been submerged by two converging arms of the sea from the north and south that formed the Western Interior Seaway. Also, notice the narrow active margin at North America's west coast, the site of convergent tectonics. This eustatic condition will not prevail with sea level progressively dropping as it fluctuated throughout the Pliocene, the Pleistocene and Holocene.
Modified from Ron Blakey and Colorado Plateau Geosystems. Inc.

Subsidence and sedimentation...
Although classified as a passive continental margin, the "active" shelf received nonmarine 
deposition through most of the Cretaceous. With the exception of the Oligocene, the Tertiary saw wave after wave of marine deposition on Maryland's subsiding shore spurned by rising global seas. During the Late Oligocene, Miocene and early Pliocene, the Chesapeake Group was deposited. The Group's lower three stratal components are exposed as wave-eroded bluffs at Calvert Cliffs. Their ~70 m of strata preserve nearly 10 million years of elapsed time. It forms the most available sequence of exposed Miocene marine sediments along the East Coast of North America.

The depocenter of the Salisbury Embayment is drowned by high seas during the Middle Miocene (15 Ma). This eustatic condition will not prevail with sea level progressively dropping as it fluctuated throughout the Pliocene, into the Pleistocene and present.
Modified from Ron Blakey and Colorado Plateau Geosystems. Inc.

The Chesapeake Group's Cliffs of Calvert...
Vacillating seas consequent to Pleistocene glaciation-deglaciation periodically flooded and exposed the land, backflooding rivers and bays such as the Chesapeake. Our present interglacial epoch - the Holocene - has re-exposed the Chesapeake Group and the Cliffs of Calvert to erosion. In spite of not having experienced a significant phase of tectonic convergence for over 200 million years, the modern Appalachian Mountains have been rejuvenated during the late Cenozoic, possibly isostatically in response to ongoing erosion or by mantle forcing. That contributed to river incision and deposition across the Coastal Plain with sedimentation such as the Chesapeake Group.

A glowing Maryland sunrise illuminates the strata of the Calvert Cliffs looking south.
Photo Courtesy of Stephen J. Godfrey, Ph.D., Curator of Paleontology, Calvert Marine Museum

North America's most easterly geomorphologic region is the siliciclastic sedimentary wedge of the Atlantic Coastal Plain that began to form with the breakup of Pangaea. It’s a low relief, gentle sloped, seaward-dipping mass of unconsolidated sediment over 15,000 feet thick, deposited on the margin of North America Appalachian-derived rivers and streams, and spread back and forth by the migrating shorelines of vacillating seas throughout the Cenozoic. In Maryland, progressing to the northwest from the Coastal Plain, one encounters the Piedmont Plateau at the Fall Line, the Blue Ridge, the Valley and Ridge and the Appalachian Plateau Provinces.

From east to west through the Appalachian orogen with an underlying Grenville basement, the physiographic provinces of Maryland are synonymous with those up and down the East Coast of North America. Notice the Fall Line, separating the Piedmont from the Coastal Plain, and the Chesapeake Bay, dividing the Plain into higher western and lower eastern subdivisions.

The five physiographic provinces are a series of belts with a characteristic topography, geomorphology and specific subsurface structural element. The overall trend is from  southwest to northeast along the eastern margin of North America. Their strike and geologic character have everything to do with the tectonic collisions that built mountains, recorded periods of quiescence, formed and fragmented at least two supercontinents, and opened and closed the oceans caught in between.

Location of Calvert Cliffs on the Chesapeake Bay's western shore of the Atlantic Coastal Plain (light colored)
Modified from USGS map

Calvert Cliffs is on the Chesapeake Bay's western shore of the Atlantic Coastal Plain, as are the major cities on the mid-east coast - Philadelphia, Baltimore, Richmond, Washington, etc. If you connect them on a map, you'll locate the approximate western boundary of the Coastal Plain called the Fall Line or Zone. It's the geomorphic break (and geographic obstacle) where a 900-mile long escarpment of falls and rapids separates the Coastal Plain from hard, metamorphosed crystalline rock of the Piedmont foothills to the west.

The Piedmont and Blue Ridge share similar types of crystalline igneous and metamorphic rocks of the core of the Appalachians. The majority of Blue Ridge rocks are related to events of the Precambrian and Cambrian from Grenville mountain building to the Cambrian rift basins, while most of the Piedmont rocks were transported and accreted to North America. A discussion of the details of tectonic derivation and geologic structure of the remaining westerly provinces is beyond the scope of this post. 

The Calvert Cliffs consist largely of relatively undeformed and unlithified strata of silts, sands and clays of the Calvert, Choptank and St. Mary's formations (Shattuck, 1904) in ascending order of the Chesapeake Group. The formations are interrupted by a series of erosional unconformities and other hiatal intervals and preserve nearly 10 million years of elapsed time.

Flag Ponds Nature Park
The cliffs in the distance are the same as the top of the post. Bluffs directly adjacent to the bay generally have very narrow or no beach material (0-3 m) and little to no vegetation on the face. The erosion rate there is historically uniform (0.3-0.6 meters per year), where they are susceptible to slumping and collapse facilitated by a slope angle of nearly 70 degrees. In this area of Calvert Cliffs and Cove Point to the south, "fossil" bluffs are stabilized and preserved inland of the shoreline as the beach acts as a barrier and protects toe slope erosion from wave action as it migrates to the south along longshore currents. At Cove Point the migrating-landform is a prograding cuspate foreland. Southward bluffs become protected from wave action as new beaches are deposited at the bluff-toes. As the foreland migrates to the south, the beach will recede and active bluff erosion will recommence. The changes induced by the foreland occur on a "decadal rather than centennial scale, which places the rate of slope failure on a human scale." This passive Atlantic margin is anything but!

The Miocene succession was deposited as a complex package representing a first-order transgressive-regressive cycle with numerous superimposed smaller-scale perturbations of sea level. Overall, the record is one of gradual shallowing within the Salisbury Embayment and is reflected in the character of the strata that progresses from inner to middle shelf to tidally-influenced, lower-salinity coastal embayments. Deposition occurred under subtropical and warm temperate conditions in a shallow marine shelf environment at a maximum water depth of more than ~40-50 meters.

The exposures include not only the Calvert Cliffs but the Westmoreland and Nomini Cliffs along the Virginia Shore of the Potomac River. Debated for more than a century, estimates for the basal Calvert range from early Early Miocene to mid-Middle Miocene. 

Miocene Stratigraphy of Calvert Cliffs
The lower Chesapeake Group's Miocene section has been subdivided using a multitude of stratigraphic systems including three formations of 24 stratigraphic beds and molluscan zones, many of which have been renamed as members based on locality. In addition, various depositional sequences and events have been described.  Dates are in millions of years (Ma).
Modified from Ward and Andrews, 2008, and Carnevale et al, 2011.

A general absence of beaches below the cliffs is a characteristic of the region. Direct wave undercutting at the cliff-toe, freeze-thaw erosion, underground seepage at sand-clay interfaces and mass-wasting (the average inclination is 70 degrees) are accompanied by rapid wave removal of colluvium (slope debris). Long-term rates can exceed 1 m/yr. Slumps, rotational slides and fallen trees are constantly being generated and removed. For these reasons, beachcombing for fossils and excavating the cliff-toes is a dangerous and prohibited venture. Collected is allowed in designated parks along the shoreline such as Calvert Cliffs State Park, Flag Ponds Nature Park and Brownies Beach, and private beaches given the owner's permission. 

Two vying factions in regards to the Cliffs are scientists that reap the benefit of ongoing erosion and the homeowners, who seek real estate in close proximity to the cliff edge for the sake of a bay view. For the former, the best way to preserve the Cliffs is to let them erode naturally, while the latter would like to riprap (with stone or concrete), bulkhead, sandbag and groin-field the Cliffs to preserve them and their property. In dealing with Mother Nature, in this regard, shoreline protection reduces the risk of cliff failure, although it doesn't eliminate it. It's only a matter of geologic time. 

Rocky Point just downbay (south) of the Calvert Cliffs Nuclear Power Plant
Exposed are the Choptank and the St. Mary's Formations, the latter often oxidized to an orange color. The boundaries between the members and subdivisions are readily discernible. Zonation of thinly laminated beds of cobbles, mollusk shells, molds and casts can be made out even at this distance. Uppermost strata (upland deposits) consists of undulating Pleistocene alluvium, possibly where Pliocene beds were beveled off during a Pleistocene embayment. Again, notice the slump and collapse material, and destabilized trees sliding down the slope from above. Many homes perched on the cliff-edge have met a similar fate.
Photo Courtesy of Stephen J. Godfrey, Ph.D., Curator of Paleontology, Calvert Marine Museum

To reach otherwise inaccessible sections of the Cliffs and lessen the inherent dangers of collapse and burial, this mode of exploration employs descent from above. Excavation into the unlithified substrate is facilitated by an air-powered drill using a scuba tank's compressed air.

From Google Science Fair 2014. See the video here.

The formations preserve more than 600 largely marine species that include diatoms, dinoflagellates, foraminiferans, sponges, corals, polychaete worms, mollusks, ostracods, decapods, crustaceans, barnacles, brachiopods and echinoderms. The macrobenthic fauna (large organisms living on or in the sea bottom) act as good indicators of salinity. The Calvert and Choptank are dominated by diverse assemblages of stenohaline organisms (tolerating a narrow range of salinity); whereas, the younger St. Mary's Formation exhibits an increasing prevalence of euryhaline molluscan assemblages (tolerating a wide range of salinity). The changes within the assemblages reflect the fluctuating freshwater conditions within the Salisbury Embayment.  

Vertebrate taxa include sharks and rays, actinopterygian fish, turtles, crocodiles, pelagic (open sea) birds, seals, sea cows, odontocetes and mysticetes (whales, porpoises and dolphins).

In addition, the Cliffs preserve isolated and fragmentary remains of large terrestrial mammals (peccaries, rhinos, antelope, camels, horses and an extinct group of elephants called gomphotheres), palynomorphs (pollens and spores), and even land plants (from cypress and pine to oak) that bordered the Miocene Atlantic Coast and were carried to the sea by floodplains, rivers and streams sourced by the Appalachians.

In the Miocene, mammalian diversity was reaching unprecedented levels, increasing in size and filling every conceivable niche on every continent. Grass-grazing, multi-stomached herbivorous artiodactyls (such as giraffes, antelopes, cattle, camel, pigs and hippopotami) were slowly replacing dominant perissodactyls (such as horses, rhinos and tapers) that developed after the end-Cretaceous extinction.  
Modified from Jay Matternes

Miocene River Environment by Karen Carr with permission

Armed with a plastic garden rake in hand from the local hardware store, I collected this fossil potpourri (below) on a brief 60 minute stroll along the beach at Flag Ponds. Their abundance and availability is a testimony to the richness and diversity of the Miocene marine fauna. The fossils are continually being generated from the eroding cliffs and their underwater extensions. 

I am uncertain as to the specific origin of the mammalian bony fragments, but I suspect they are largely from marine fauna (i.e. dolphin, whale, seal, etc.) rather than terrestrial, since the former vastly outnumber the latter. Cetaceans such as the whale have repurposed an air-adapted mammalian ear for the differentiation of underwater sounds. The shell-like otic tympanic bulla is a thickened portion of the temporal bone located below the middle ear complex of bones. The large dense bone is well preserved and can easily be mistaken for an eroded fragment of rock.

The crocodile tooth is an indication that rivers and swampy habitats existed in the marginal marine environment of Calvert Cliffs. Shark teeth are the most common vertebrate fossils preserved at the Cliffs. Their numbers are commentary on the favorable paleoenvironmental conditions that existed in the Salisbury Embayment. Of course, sharks continually produce and shed teeth throughout their lives, facilitated by the absence of a long, retentive root structure, and are composed of durable and insoluble biogenic apatite, which favors their preservation. Calvert Museum collections contain as many as 15 genera. The main constituents are Carcharhinus, Hemipristis, Galeocerdo, Isurus and Carchrius. Carcharhiniformes shed about 35,000 teeth in a lifetime!

Appearing in the fossil record about 395 million years ago (middle Devonian), the Class Chondrichthyes (cartilaginous skeletal fish) is divided into two subclasses: Elasmobranchii, which includes sharks, rays and skates, and Holocephali (chimaeras). Elasmobranchii are distinguished by their 5-7 pairs of gill clefts, rigid dorsal fin, presence or absence of an anal fin, placoid dermal scales, teeth arranged in series within the jaws and the upper jaw being not fused to the cranium. Along with a dolphin tooth and a few gastropods, here are a few specimens collected from the surf at Calvert Cliffs State Park, about five miles southeast of Flag Ponds. 

Top Row: Hemipristis (Snaggletooth shark), Isurus (?), Carcharhinus (?)
Middle Row: Carcharhinus (?), Hemipristis (?), Porpoise tooth, Hemispristis (?)
Bottom Row: Ray plate, Turritella shell, ray plate, Scaphopoda mollusc shell.
Any corrections or additional insight regarding these fossils is welcomed.

From these small samples, one can glean the ancient habitat at Calvert Cliffs during the Miocene. The combined study of both fossils and rock layers are essential in reconstructing the paleo-geography of the Cliffs. 

By far, the largest and rarest shark teeth at Calvert Cliffs (but widely distributed within the world's oceans) are those of a "Megalodon," an extinct species of shark that lived from the late Oligocene to early Pleistocene (~28 to 1.5 million years ago). Its distinctive triangular, strongly serrated teeth are morphologically similar to those of a Great White shark (Carcharodon carcharias), a fact that fuels the debate over convergent dental evolution versus an ancestral relationship.

An allometric relationship exists between tooth width and body length in modern sharks. A tooth that is 5.5 inches wide correlates with a body length of 60 feet, making Megalodon the largest shark to have lived, weighing as much as 100 tons. I calculated this Megalodon tooth in my collection to come from a 49 footer. That's ten feet longer than a school bus!

The controversy has resulted in a taxonomic name of either Carcharodon megalodon or Carcharocles megalodon - commonly abbreviated as C. megalodon. The “Meg” is regarded as one of the most powerful apex predators in vertebrate history. On rare occasion, extinct cetacean fossilized vertebrae have been uncovered with bite-marks suggestive of mega-tooth shark predation or scavenging. Megalodon is represented in the fossil record exclusively by teeth and vertebral centra, since cartilaginous skeleton is poorly preserved.

C. megalodon dining on cetaceans
With permission from artist Karen Carr

Dr. Stephen Godfrey of the Calvert Marine Museum has been conducting paleontological studies in the Calvert Cliffs for some 15 years. After rafting along the shoreline to the excavation site, this paleontologist is taking measurements of a trace fossil interpreted as an infilled tilefish burrow from the Plum Point Member of the Calvert Formation deposited some 16 million years ago. In a 2014 paper in the JVP (see reference below), well preserved,  partially complete, largely cranial remains of tilefish are described. They have been collected over the past three decades from Miocene deposits outcropping in Maryland and Virginia. 

Ruler in hand, paleontologist W. Johns investigates the exposed tilefish burrow.
Photo Courtesy of Stephen J. Godfrey, Ph.D., Curator of Paleontology, Calvert Marine Museum

Lopholatilus ereborensis, a new species of family Malacanthidae and teleost (infraclass of advanced ray-finned fish), inhabited long funnel-shaped vertical burrows that it excavated for refuge within the cohesive bottoms of the outer continental shelf of the Salisbury Embayment that likely inhabited other parts of the warm, oxygenated waters of the western North Atlantic outer shelf and slope. The species name was derived from 'Erebor,' the fictional name for the Lonely Mountain in J.R.R. Tolkien's The Hobbit. Like the mountain-clan of dwarves, the tilefish mined the substrate.

This is a close-up view of an infilled, cylindrical-shaped, tilefish-excavated burrow in erosional cross-section. Investigations of extant tilefish show they were shelter-seeking within horizontal clay substrates. The tilefish used as a head-first entrance and tail-last exit for protection from predators. The burrows were subject to infill and collapse, taphonomously preserving the tilefish if within.
Photo Courtesy of Stephen J. Godfrey, Ph.D., Curator of Paleontology, Calvert Marine Museum

Schematic drawing showing three Miocene tilefish burrows. The fish on the left is actively excavating a new burrow. In the center, the burrow has been infilled, preserving the fish that habitated the burrow. On the right, the fish has taken refuge within its burrow.
Photo Courtesy of Stephen J. Godfrey, Ph.D., Curator of Paleontology, Calvert Marine Museum

Lopholatilus ereboronsis moderately deep skull and short snout in left lateral view with interpretive illustration. For orientation, the large circular structure is the orbit with anterior to the left. Post-cranial structures (vertebral skeleton) are missing. The fossil preserves anatomical detail as if a live dissection. One can clearly differentiate the entire suspensorium (jaw connections) of the maxilla (upper jaw) and a few teeth, the dentary (lower jaw) and the quadrate (ancestral jaw-joint), etc. Five extant genera of tilefish inhabit the waters of the Atlantic, Indian and Pacific Oceans.
Photo Courtesy of Stephen J. Godfrey, Ph.D., Curator of Paleontology, Calvert Marine Museum

In an attempt to see what fossilized remains might have filtered down from overlying Miocene and more recent strata, I walked the beach until finding a break where a wash had carved a trough through the bluffs. I immediately spotted a white object glistening in the sun in a stream bed filled with gravel and tiny sharks teeth that turned out to be the worn remnants of a Colonial-era smoking pipe.

Pipes of clay were first smoked in England after the introduction of tobacco from Virginia in the late 16th century. Sir Walter Raleigh, an English sea captain, was one of the first to promote this novel habit acquired from Native Americans that had practiced its ritual use for many centuries. By the mid-17th century clay pipe manufacture was well established with millions produced in England, mainland Europe, and the colonies of Maryland and Virginia. For various reasons, clay pipe demand declined by the 1930’s.

Clay pipes were very fragile and broke easily, and along with their popularity, they are commonly found at Maryland and Virginia colonial home sites. In Colonial-era taverns, clay pipes that were passed around were supposedly broken off at the stem for the next user in the interest of hygiene. Some clay pipes can be dated by the manufacturer's stamp located on the bowl, which was unfortunately missing in this lucky but well calculated find.

• Evolution of Equilibrium Slopes at Calvert Cliffs, Maryland by Inga Clark et at, Shore and Beach, 2014.
 • Frequency of Effective Wave Activity and the Recession of Coastal Bluffs: Calvert Cliffs, Maryland by Peter R. Wilcock et al, Journal of Coastal Research, 1998.
• Geologic Evolution of the Eastern United States by Art Schultz and Ellen Compton-Gooding, Virginia Museum of Natural History, 1991.
• Maryland's Cliffs of Calvert: A Fossiliferous Record of Mid-Miocene Inner Shelf and Coastal Environments by Peter R. Vogt and Ralph Eshelman, G.S.A. Field Guide, Northeastern Section, 1987.
• Miocene Cetaceans of the Chesapeake Group by Michael D. Gottfried, Proceedings of the San Diego Society of Natural History, 1994.
• Miocene Rejuvenation of Topographic Relief in the Southern Appalachians by Sean F. Gallen et al, GSA Today, February 2013.
• Molluscan Biostratigraphy of the Miocene, Middle Atlantic Coastal Plain of North America by Lauck W. Ward, Virginia Museum of Natural History, 1992.
• Slope Evolution at Calvert Cliffs, Maryland by Martha Herzog, USGS.
• Stargazer (Teleostei, Uranoscopidae) Cranial Remains from the Miocene Calvert Cliffs, Maryland, U.S.A. by Giorgio Carnevale, Stephen J. Godfrey and Theodore W. Pietsch, Journal of Vertebrate Paleontology, November 2011.
• Stratigraphy of the Calvert, Choptank, and St. Mary's Formations (Miocene) in the Chesapeake Bay Area, Maryland and Virginia by Lauck W. Ward and George W. Andrews, Virginia Museum of Natural History, Memoir Number 9, 2008.
• The Ecphora Newsletter, September 2009.
• Tilefish (Teleostei, Malacanthidae) Remains from the Miocene Calvert Formation, Maryland and Virginia: Taxonomical and Paleoecological Remarks by Giorgio Carnevale and Stephen J. Godfrey, Journal of Vertebrate Paleontology, September 2014.
Variation in Composition and Abundance of Miocene Shark Teeth from Calvert Cliffs, Maryland by Christy C. Visaggi and Stephen J. Godfrey, Journal of Vertebrate Paleontology, January 2010. 

I wish to express my gratitude and thanks to Stephen J. Godfrey, PhD., Curator of Paleontology of the Calvert Marine Museum, for providing valuable support (personal communications, October 2014), documentation and photographs of Calvert Cliffs and his recent excavation and publication.

Calvert Cliffs Marine Museum was founded in 1970 at the mouth of the Patuxent River in Solomons, Maryland. Visit them here, but do go there! You can join the museum here.

The Ecphora is the quarterly newsletter of the Calvert Marine Museum Fossil Club. Ecphora gardnerae gardnerae is an extinct, Oligocene to Pliocene, predatory gastropod and the Maryland State Fossil, whose first description appeared in paleontological writings as early as 1770. Sadly, riprapping (rock used to protect shorelines from erosion) has covered one of only two localities in the State of Maryland where the fossil can be found. The other is on private land and off limits without permission. Ironically, Marylanders can find their state fossil in Miocene strata of Virginia. Download copies of current and past newsletters here or simply subscribe.