Fossil Landscape Revealed: Reading the Rocks in New England Summits

It’s remarkable to think that we are discovering ice on a dwarf planet 4.67 billion miles (7.5 billion kilometers) away from Earth, at a time when we are still unraveling clues to the ice that once shaped this planet.

Two New England geologists have spent years studying the rocks and traces left by ancient glaciers in the White Mountains, the northern stretch of the Appalachian Mountains in New Hampshire and Maine. This past October, they co-authored a paper in Geology with 3 other scientists.  And in it, they revealed that the highest summits in New England were covered by solid ice during the Last Glacial Maximum.

 

View from the summit of Mount Moriah in New Hampshire looking at the White Mountains’ Presidential Range; image by Cappi Thompson at Getty Images.

 

But what does this mean? And why should we care?

“This question about whether or not the New England summits were covered by an ice sheet is long standing, going back over 100 years,” explained Dr. P. Thom Davis by phone.  “And one reason this question is important is because continental ice sheets take a long time to build up, and as they build up, they reduce global sea level.   So ice sheet thickness has implications far beyond just New England.”

Dr. Thom Davis of Bentley University and Dr. Paul Bierman of the University of Vermont actually wrote and presented the paper at the annual Geological Society of America conference in 1999, but they didn’t publish it until 2015.

“We sent a draft around informally to some colleagues,” said Dr. Davis, “and they sort of were giving us a hard time, wanting us to go back and rethink a lot of the implications. And then one thing led to another, and we just kept rethinking and rethinking for the next 15 years.”

“It was a much more radical proposition in 1999 than it is today,” explained Dr. Bierman. “Since then a whole lot of work has come out of the Arctic. So when we finally submitted this now, I guess it was a surprise, but it wasn’t unexpected.”

That ‘radical proposition’ involved whether or not ice covered the mountains, whether it was a certain type of ice, and therefore whether it did or did not preserve “fossil” or “relic” landscapes.   These ideas have been pondered (or dismissed) by various geologists since the mid 1800s.

While the term “fossil landscape” might inspire images of preserved prehistoric environments suffused with traces of ancient life, this is not at all what it means.  Rather, it refers to the geology left behind by cold-based ice–ice frozen all of the way to the ground–that both shielded rocks from the effects of cosmic rays and slowed erosion.

Think of how much impact an enormous sheet of ice can have on an environment.  When ice is not completely frozen to the ground (warm-based ice), water runs through it, pulling dirt, rocks–and the glacier itself!–along with it.  The ground erodes; the debris is carried elsewhere. Remnants can be seen in boulders scattered throughout New England.

Notice the shape of the valley in Crawford Notch, NH.  This valley is a result of glacier ice moving through the environment, albeit at a remarkably slow speed. Image by Mark Zelasko at Getty Images.

Boulder in Salisbury, NH

 

Detail of boulder in Salisbury, NH

Images of a boulder (perhaps a glacial erratic: a rock carried by a glacier and deposited in another location in geologic terms) in Salisbury, NH; photos taken by the author

 

“The word ‘fossil landscape’ sort of worried me from the get-go because of how it might be misconstrued to having more of a biological context, like mammoth bones,” stated Dr. Davis, in reference to the press release describing their work. “We’re looking at the age of exposure, the length of time those surfaces have been exposed to the cosmic ray bombardment.”

Drs Davis and Bierman collected samples near to or on the summits of Mt. Katahdin in Maine and Mt. Washington and Little Haystack Mountain in NH during the 1990s.  Their ‘radical’ suspicion–that these summits were indeed covered by solid ice–could only able be proven recently with advanced technology.

Before that, they–like their peers in the last two centuries–relied on visible clues: the type of rock on summits and in valleys, striations (or grooves) in the rocks that may have been made by  ice, the type of sediment in the valleys and whether this indicated the type of glacier that might have helped create them.  And one of the biggest clues?

Erratics.

“That is,” Dr. Davis explained, “stones that have been transported from another location.”

“Two centuries ago, scientists might have argued [that erratics] were deposited in these high locations by great floods,” he continued. “But that pretty much ended with Agassiz’s glacial theory in the middle of the 1800s.”

He is referring to Louis Agassiz, an eminent Swiss biologist and geologist who taught at Harvard, and perhaps the first to support the idea that these summits were covered by an ice sheet.  It is important to note, however, that he believed that ice sheet was a local glacier rather than a vast continental ice sheet.

Prior to this, geologists such as Charles T. Jackson–the first NH State Geologist–or Edward Hitchcock (of trace fossil fame) believed that a flood complete with icebergs was responsible for misplaced boulders. Striations could be explained by the force of rock against rock from powerful currents within that water.

British citizens Mary Horner Lyell and her husband, Charles–another well-known geologist from the 1800s–explored these mountains in 1845, including a trip up Mt. Washington on horseback. Lyell attributed erratics to melting icebergs.

Frozen tower and communication equipment at the summit of Mt. Washington; image by Onfokus at Getty Images.  Charles Hitchcock — son of Edward and Orra Hitchcock — helped create this year-round weather station.  He was a NH State Geologist and a Dartmouth professor. 

NH geology took a step forward with James W. Goldthwait and then later his son, Richard, in the 1900s.  They proposed that New England summits were covered by solid ice–not warm-based ice–and by a continental–not a local–ice sheet.

“[James W. and Richard P. Goldthwait] recognized this importance long ago, from the turn of the last century,” said Dr. Davis. ‘They both recognized very fresh looking erratics. The only way erratics can arrive on these summits is by continental ice sheets.”

“They made a really good case that the last ice sheet that dropped these erratics on the summits happened during our last glaciation about 20,000 years ago. [I]f the summits had been nunataks during the last major glaciation about 20,000 years ago, then the erratics should have been more weathered, the soils should have been more developed on the summit areas, and the bedrock should have been more weathered, as well.”

Baxter Peak of Mount Katahdin in Baxter State Park, Maine. View from Knife Edge Trail; image by Posnov at Getty Images.

Mount Katahdin is the highest mountain in Maine at 5,268 feet (1,606 m). Katahdin is the centerpiece of Baxter State Park: a steep, tall mountain formed from underground magma; image by Simon Massicotte at Getty Images.

The debate about the type of ancient ice in the White Mountains was dropped for a few decades, slowly regaining interest in the 1970s.  But it wasn’t until the recent paper by Drs. Bierman and Davis that proof lent itself to solving the issue.

“[Our method was to] count the abundance of very, very rare isotopes,” Dr. Bierman explained, “And, by that we mean isotopes of the element beryllium and the element aluminum.”

“The beryllium isotope with a total mass of 9 is the normal stuff that you find in nature. The beryllium isotope with a total mass of 10 per atom is extremely rare. And in order to measure these isotopes, we needed the technical ability to do that, and that didn’t come about until the late 1970s with a device called the accelerator mass spectrometer. These are very large, very expensive, difficult to maintain, and rare beasts. Over the past 30 years, they’ve been used increasingly by geologists to make the kinds of measurements that we did.”

“We also used cosmogenic carbon-14,” he continued, “which is an isotope with a much shorter half-life, about 5,730 years. And what that means is that when a rock is exposed to cosmic rays at the surface and then buried, that carbon 14 disappears much more rapidly than beryllium 10 and aluminum 26 isotopes.

“[Data from the accelerator mass spectrometer] tells us the [exposure] age because we can count the number of carbon-14 atoms, just like we can count the beryllium-10 atoms. We know that these are produced at a certain rate every year. It’s a very low rate.

“For beryllium-10, it’s just a few atoms per year per gram of material that we’re measuring. It’s a little bit more for carbon-14.  And since we know how quickly they’re made and we can count how many atoms there are, we can calculate an age–or a residence time–near the surface.”

“A lot of these ages from our exposure dating,” added Dr. Davis, “were coming out much older than we expected, much older than the last glaciation from the summits of both Katahdin and Mt. Washington.”

 


A view of Mt Washington and Mt Madison along some farmland in Shelburne, New Hampshire during winter; image by Cappi Thompson at Getty Images.

“I think the Goldthwaits were primarily looking at these kinds of qualitative data, like how fresh the erratics in the bedrock were,” Dr. Davis offered. “And based on that, they probably weren’t exposed very long.  But as it turns out, weathering varies dramatically to different latitudes, so is not a very quantitative method. That’s all we had, though, until these cosmogenic radionuclides became available for measuring.”

“The main point of our geology paper is that, apparently, even at temperate latitudes, the higher elevations may have been overrun by ice sheets that were frozen to the bed, leaving what we call ‘relic landscapes,'” he concluded.

“From a geologic point of view,” Dr. Bierman continued, “it points to the complexity of the evolution of the New England landscape. It’s another piece of the puzzle in how this landscape evolved over time.”

 


Sunrise clouds above the White Mountains’ Presidential Range in Jefferson, New Hampshire; image by Cappi Thompson at Getty Images.

Old_Man_of_the_Mountain_4-26-03

 

Old Man of the Mountain–an iconic NH rock formation, one that seems appropriate to share in a blog post on geology–on April 26, 2003, seven days before the rocks of its face collapsed. A late spring snow fell the night before. Image by Jeffrey Joseph, public domain, Wikipedia.

Dr. P. Thom Davis and Dr. Paul Bierman not only introduced me to a new science, they also piqued my interest in it. Basic geologic vocabulary was foreign to me. I delighted in discovering the meaning behind new words (nunataks, moraines, varve records, basal thermal regime!) in order to better understand their work. Thanks to their time and their research, I now look at the world around me with much more discerning eyes, especially at the many boulders erratics that scatter the landscape.  Fossils in New England may be scarce, but rock formations are not.  I extend a sincere and resounding THANK YOU to both, for their help, their graciousness and the fun three-way conversation we had discussing their paper!

Thank you to Kea Giles at the Geological Society of America for sending me a copy of the paper!

I highly recommend the book “The Geology of New Hampshire’s White Mountains” shown below, co-authored by Dr. P. Thom Davis. It is a fascinating account of NH geology and a great introduction to geology itself.

Woodrow Thompson, another co-author of that book, wrote an engaging account of the history of NH geology (paper is listed below). It was a great help to me in writing this piece, and I encourage anyone interested to read it

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References:

  1. Fossil Landscapes in New England, GSA press release, October 26, 2015
  2. Cold-based Laurentide ice covered New England’s highest summits during the Last Glacial Maximum, Paul R. Bierman, P. Thompson Davis, Lee B. Corbett, Nathaniel A. Lifton, Robert C. Finkel, Geology, October 2015
  3. History of Research on Glaciation in the White Mountains, New Hampshire (U.S.A.), Woodrow B. Thompson, Géographie physique et Quaternaire, Volume 53, 1999
  4. The Geology of New Hampshire’s White Mountains, J. Dykstra Eusden, Woodrow B. Thompson, Brian K. Fowler, P. Thom Davis, Wallace A. Bothner, Richard A. Boisvert, John W. Creasy; Durand Press, 2013

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Strange Monsters and Turkey Tracks

Mary Anning was only 5 or 6 years old when she started down the path of discovery; Edward Hitchcock was in his late 30’s. Born on different continents 6 years and 3 days apart, both contributed to a world in which science was blossoming in new and exciting directions.

Their lives couldn’t have been more different.

Mary Anning was born May 21, 1799, to Molly and Richard Anning.  She and her older brother, Joseph, were the only children out of ten to survive to adulthood.  They learned from their father how to find fossils along the shore of their home in Lyme Regis, England. Mary accompanied her father on these hunts from age 5 or 6.  She learned how to excavate fossils from the rock, how to polish them, how to sell them to local tourists.

Lyme Regis, Dorset looking along the beach towards Charmouth, with the promenade to the left. The coast contains many fossils in the rocks which draws tourism from around the globe. Photo by Chris Hopkins, courtesy Getty Images. This is where Mary Anning searched for fossils throughout her life.

*****

When she was 11, Mary found her first major discovery: the complete skeleton of the first known ichthyosaur. Her brother had found its skull the year before—the same year that their father died—and she had gone back to excavate further.

Its discovery puzzled scientists at the time. Extinction and evolution were concepts that had yet to be introduced. The first dinosaur, Megolosaurus, would not be named until 13 years later; the actual term ‘dinosaur’ would not appear until 1842.  So this skeleton, with components recognized as those of lizards and fish, was utterly alien to the world.

 

Yale Peabody - Ichthyosaurus detail

Yale Peabody - Ichthyosaurus

Images of Stenopterygius quadricissus at the Yale Peabody Museum; this is a “thunnosaur ichthyosaur”, as described here at Wikipedia.  In any case, not the exact type of ichthyosaur–a marine reptile that co-existed with dinosaurs–discovered by Mary Anning, but it is something similar. Photos taken by the author.

*****

And it was just one of many new species Mary would go on to discover in her lifetime.

In 1823, she would find the skeleton of what was eventually known as Plesiosaurus giganteus. Five years later, she would find a pterosaur (Dimorphodon).  She discovered a transitional fossil—one that actually demonstrates in its skeleton traits that show it is evolving from one form to another—in 1829. That became known as Squaloraja polyspondyla. In 1830, she found another plesiosaur: Plesiosaurus macrocephalus.  Ultimately, she would also discover 34 new species of ancient fish.  She correctly identified fossilized dung within ichthyosaur skeletons, a type of fossil newly named coprolites and described by William Buckland after discussions with Mary Anning and Gideon Mantell.

 

DSP - diorama detail

Part of a life-size diorama at Dinosaur State Park, Rocky Hill, CT; replicas of Dimorphodon, a pterosaur discovered by Mary Anning in 1828, can be seen in the top right. Photo taken by the author.

Squaloraja_polyspondyla

Image of Squaloraja polyspondyla, a type of fossil discovered by Mary Anning in 1829. You can read about this in more detail at the blog Mary Anning’s Revenge here

Plesiosaurus_macrocephalus_mary_anning

Drawing of Plesiosaurus macrocephalus discovered by Mary Anning in 1830; image courtesy of Brian Switek and Wikipedia

Beneski - great vertebrae from ichthyosaurus

Beneski - great vertebrae ichthyosaurus sign

Images of a polished section of Ichthyosaurus communis vertebrae in a drawer at the Beneski Museum at Amherst College.  Not only does this come from Lyme Regis, but this is the type of Ichthyosaur discovered in 1832. Mary Anning found the skull and was convinced that there was nothing more to be found. Fellow-fossil hunter Thomas Hawkins, however, believed there was more.  She led him to where she’d found the skull, and he and his team did find the rest of the skeleton.  When the skeleton shattered as they moved it, Mary Anning helped Hawkins put it together.

*****

Her discoveries fueled scientific revelations, were studied by the most prominent scientists of the age, and were discussed in the relatively new Geological Society of London.

As a woman, she was never allowed to attend any of their meetings or lectures.  Moreover, she was almost never credited for her remarkable fossil finds.

Her male friends could attend university (as both a woman and a member of the Dissenter religion, this was not an option), join scientific organizations, have papers published, discuss the latest scientific research among peers in professional institutions, travel extensively (without chaperones) and make substantial financial gains in their careers.

Mary’s life was marked by periods of financial gain and of teetering terribly close to financial ruin. She had three years of formal education.  She traveled to London once.

And yet, she constantly persevered. Her work enabled her to buy a home for her family at the age of 27, the first floor of which she created her fossil shop.  Although she was not privy to university resources, she taught herself scientific illustration.  Using marine life from the local beach, she taught herself anatomy through dissection.  She was in communication with and visited by scientists from all of Europe.

Illustration of Mary Anning selling fossils by Dorling Kindersley (DK), courtesy Getty Images.

In fact, some of the very same people in communication with Edward Hitchcock were communicating with or visiting Mary Anning: Charles Lyell, Roderick Murchison, Richard Owen, Gideon Mantell, and William Buckland.

Across the ocean, Edward Hitchcock was born in Deerfield, Massachusetts on May 24, 1793, several years before Mary Anning was born.  He would also outlive her.  While she died of breast cancer at the age of 47, Edward died at 70.

Had he been African-American (or simply African) in the newly-formed United States or a woman anywhere, his opportunities would have been severely limited, but he was none of those things.  Still, although he hoped to study astronomy at Harvard, he ultimately never attended college.

He did, however, become the first state geologist for Massachusetts in 1830 (the same year Mary made one of her major fossil discoveries).  He created the first geologic map of Massachusetts—only the 2nd ever created in the country—in 1832.  He believed the state exhibited proof of the Great Flood referenced in the Bible; it was later found to be remnants of the Ice Age.

 

DSP - sign New England ichnology

Sign at Dinosaur State Park that offers a brief history of ichnology in New England. Edward Hitchcock is pictured at the very top. Below that, a drawing of the fossil tracks found by Pliny Moody–a name you will see in marble in the “Donors to the Footmarks” frame further below. Photo taken by the author

*****

Remarkably, he believed that women should receive education and learn about science. One of his well-known students was Mary Lyon, a woman who went on to found Mount Holyoke Female Seminary (now known as Mount Holyoke College), among some of the country’s first academic institutions for women. Orra White Hitchcock, who married Edward in 1824, was a prolific artist and scientific illustrator.  She created many of the illustrations he used in his classes.

Classroom chart on linen drawn by Orra White Hitchcock, Amherst College.

Drawing of plesiosaurus skeleton by Orra White Hitchcock, 1828 – 1840, Classroom chart on linen, courtesy of the Archives & Special Collections at Amherst College

 

In 1835, things changed abruptly.  Dr. James Deane, from a nearby town, wrote to Edward about tracks found in stone slabs that were to be used to build a sidewalk.  Edward dismissed their importance until the surgeon sent him plaster casts of the tracks.

Most people referred to these tracks, seen in other local stone slabs, as “turkey tracks”.  Edward believed they were created by birds.  It was a belief he would defend for the rest his life, despite new discoveries that may have indicated otherwise.

Wild turkey tracks in snow

Wild turkey tracks in the snow, late Spring, New England; photo taken by the author

Wild turkey in Fall

Wild turkey in the Fall, New England; photo taken by the author

In part, his theory made sense.  The tracks looked remarkably similar to the familiar tracks of extant turkeys, and fossils of any ancient creatures responsible for the tracks in stone were not found.  New England, with its acidic conditions and lack of fossil-preserving stone, is not fossil-friendly.

Edward created a new science he named “ornithichnology,” a name that references birds, but was later shortened to just “ichnology” by William Buckland.

Beneski - 1802 footprints

Beneski - 1802 footprints

Images of the first documented fossil footprints, discovered in 1802, displayed at the Beneski Museum at Amherst College, part of the Hitchcock collection. Photos taken by the author

Beneski - gem of Hitchcocks collection

Fossil tracks displayed at the Beneski Museum at Amherst College. According to Window into the Jurassic World by Nicholas G. McDonald, these tracks were the “gem” of Hitchcock’s collection (pg. 58, Figure 6-8). This slab was originally used as paving. Photo taken by the author (of this blog)

*****

While major discoveries of reptiles and dinosaurs were starting to pepper European science, Edward continued studying fossil tracks and traces.  He wrote about his work and his theory to the men on the forefront of these discoveries (as mentioned earlier, women were not allowed or, apparently, credited). He began publishing books and submitted papers to the Yale American Journal of Science.

Richard Owen disagreed with Edward’s findings at first.  He would eventually change his mind after describing an extinct bird in 1939 (the ‘moa’ of New Zealand).  In 1841, Charles Lyell actually visited Edward and became a prominent supporter.

Although Mary Anning discovered and identified coprolites more than 15 years earlier, Edward discovered these fossils in 1844 in Chicopee Falls, Massachusetts.

Beneski - coprolites

Coprolites displayed in a drawer at the Beneski Museum at Amherst College.  These are not necessarily those discovered by Edward Hitchcock in 1944. Photo by the author

 

His two major works outlining his life’s work were published in 1858 (“Ichnology of New England“) and then two years following his death in 1865 (“Supplement to Ichnology of New England“).

He maintained that these fossil tracks were made by birds, and his work was heavily influenced by his desire to find proof of God in nature. In his own words, he taught “natural theology.”

 

DSP - Ichnology Hitchcock

The book Ichnology of New England, written by Edward Hitchcock in 1858; copy displayed at Dinosaur State Park. Photo taken by the author

DSP - Supplement Ichnology Hitchcock

The Supplement to the Ichnology of New England, written by Edward Hitchcock but published posthumously in 1865copy displayed at Dinosaur State Park. Photo taken by the author

Beneski - Hitchcock - donors sign

Framed marble sign highlighting donors and the amount donated; displayed at the Beneski Museum at Amherst College; photo taken by the author

 

His efforts as college president in the 1840’s prevented the closure of Amherst College.  One of his particularly successful years was the same year that Mary Anning passed away, 1847.

Today, his vast collection–thousands of fossil footprints and traces–reside in the elegant Beneski Museum of Natural History.  We are extremely fortunate, as Edward Hitchcock made it very clear he did not want his collection owned by anyone who did not share his evangelical Christian views.  Although the college moved to a more secular philosophy, his family did not honor this request.

Beneski - racks of Hitchcocks trace fossils

A small section of the Hitchcock collection of fossil tracks and traces at the Beneski Museum of Natural History at Amherst College.  This author encourages anyone interested to visit this amazing museum. Photo by the author

*****

Did Mary Anning and Edward Hitchcock know of each other across the Atlantic?  Did their names or their work ever come up in conversation? Did their mutual friends in science discuss them with the other?

There is no evidence to suggest this.

But the world would be increasingly changed thanks to their contributions, their dedication and their lifelong efforts.

Mary Anning Painting

Mary Anning painting” Credited to ‘Mr. Grey’ in Crispin Tickell’s book ‘Mary Anning of Lyme Regis’ (1996) – Two versions side by side, Sedgwick Museum. According to the Sedgwick Museum, there are two versions. The earlier version is by an unknown artist, dated before 1842 and credited to the Geological Society. The later version is a copy by B.J. M. Donne in 1847 or 1850, and is credited to the Natural History Museum in London. Licensed under Public Domain via Commons.

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References:

  1. The Fossil Hunter: Dinosaurs, Evolution, and the Woman Whose Discoveries Changed the World by Shelley Emling, 2009, Palgrave Macmillan
  2. Window into the Jurassic World by Nicholas G. McDonald, 2010, Friends of Dinosaur State Park and Arboretum, Inc.
  3. Curious Footprints: Professor Hitchcock’s Dinosaur Tracks & Other Natural History Treasures at Amherst College by Nancy Pick & Frank Ward, 2006, Amherst College Press
  4. Amherst College Archives & Special Collections – Edward & Orra Hitchcock: https://www.amherst.edu/library/archives/holdings/hitchcock
  5. Amherst College Digital Collections: https://acdc.amherst.edu

 

Locations:

  1. Dinosaur State Park, Rocky Hill, CT
  2. Beneski Museum of Natural History, Amherst College, Amherst, MA
  3. Yale Peabody Museum, New Haven, CT
Classroom chart on linen drawn by Orra White Hitchcock, Amherst College.
One of 61 drawings done by Orra White Hitchcock for use in Professor Edward Hitchcock’s classes on geology and natural history. This is a reproduction of a preexisting drawing. Pen and ink on linen, Mastodon maximus skeleton, 1828 – 1840, courtesy of the Archives & Special Collections at Amherst College