This was a big over arching piece I did to satify my interest Lake Champlain. I had alway been interested in the geology of the beautiful state I call home, so this paper was particularly fun. Hope you enjoy it as much as I did!
The Geologic History of the Champlain Valley
Massive mountain ranges, deep valleys, saltwater oceans, and towering glaciers; these are not the usual images one thinks of when contemplating the tranquil Champlain Valley. A billion years ago the Champlain Valley, along with the entire Earth, was much different than it is at present. Today this small, and sometimes forgotten region of the northeast is filled with beautiful rolling hills and stocky snow capped mountains. However, the Champlain Valley has a long history, extending far before terrestrial life had evolved. The only life on the planet was a wide variety of microscopic plants, bacteria and a few primitive eukaryotes within the ocean. Glaciation started about three million years ago and continued to about 12,000 years ago. The glaciers moved from the northwest over the landscape causing rocks and boulders to be dragged beneath the ice. These acted like dams and forced the water in the Champlain Valley to pool in a huge lake – Lake Vermont. At its height, Lake Vermont had a surface elevation around 500 feet higher than Lake Champlain’s current level. As the glaciers melted ocean waters flowed in from the Atlantic forming the Champlain Sea. The Champlain Valley is complex, a geologist’s dream, and contains many ancient sites, some of which are found nowhere else on the planet. Its history is just as complex, and in order to truly understand it one must start from the very beginning of our solar system’s existence.
The various planets are thought to have formed from the disc-shaped cloud of gas and dust left over from the Sun's formation, through the process known as accretion, in which the planets begin as dust grains in orbit around the central protostar, and eventually accumulate more and more mass as the particles collide together. Eventually these grains form into rocks, and boulders, then asteroids, and finally into small planets. In the case of the terrestrial planets they ceased accumulating matter about 100,000 years after the formation of the Sun. Only collisions with other Planetesimal allowed the terrestrial planets to grow to their present sizes.
The gas giants formed further out than the terrestrial planets. Ices were more abundant on the Jovian planets than the metals and silicates that formed the terrestrial planets, allowing the Jovian planets to grow massive enough to capture hydrogen and helium, without becoming as dense and the terrestrial planets. Uranus and Neptune probably formed closer to the Sun—near or even between Jupiter and Saturn—and later migrated outward due to the gravitational pull of Jupiter and Saturn. Between three and ten million years ago the Sun's solar wind would have cleared away all the gas and dust in the protoplanetary disc, blowing it into interstellar space, ending the growth of the planets.
Earth formed around 4.54 billion years ago from the same disk of dust and gas from which the sun itself coalesced and was largely completed within 10-20 million years. The proto- earth grew by accretion and was bombarded by objects ranging in size from dust particles to small planets until its interior was hot enough to melt the heavy metals that made up the majority of its substance. As the earth cooled the very first atmosphere formed, which may have been made up of hydrogen gas. However, hydrogen is very lightweight and reactive, so most of it would have floated off into space or reacted with other substances, leaving the atmosphere to be filled with other gasses. The first functioning atmosphere is theorized to have formed due to the volcanic activity and other chemical reactions taking place at the time. It is thought that H2O, CO2, CO, and N2 initially made up Earth’s atmosphere for the first 1 billion years, but over 3.5 billion years, the amount of CO2 in our atmosphere decreased as it became incorporated into rocks. Plate tectonics and erosion have destroyed all rocks from this time, but the different temperatures at which molten iron and silicate minerals solidify indicate that as it cooled the Earth eventually segregated into an iron core and silicate mantle approximately 2-4 billion years ago.
Lake Champlain is the sixth largest freshwater body in the United States, covering 435 square miles with almost 600 miles of shoreline. Nearly all of the Vermont shoreline is composed of sedimentary rocks - limestone, dolostone, quartzite - which were deposited in the shallow tropical sea that made up the Champlain basin about 500 million years ago. The Champlain Basin as is it known today did not exist a billion years ago. However, mountain-building events had formed a huge range of mountains that were as large as the Himalayas are today. These mountains, which were the original Adirondacks, were situated on the shoreline of the prehistoric continent of Laurentia, with a shallow tropical sea extending to the south and east. Over 500 million years the Adirondacks slowly succumbed to erosion, reducing them from 20,000 feet tall to the Adirondack Mountains seen today.
About 600 million years ago, tectonic forces caused the surface of the earth to rift. The ocean that formed was the Iapetus Ocean and was filled with fossilized coral reefs that give scientists an idea of the kinds of life that lived in this area over 450 million years ago, such as: trilobites, cephalopods, bryozoans, gastropods and primitive corals. Further tectonic activity caused the Iapetus Ocean to narrow, eventually closing completely. In the last phases of closure, the opposite sides of the ocean collided causing the ground to fracture and fold, forming a new massive mountain range the, Appalachian Mountains. The Green Mountains were formed as part of this Appalachian range some 450 million years ago. They too, like the Adirondacks have eroded to a fraction of their original size. The tremendous forces it took to create the Green Mountains can still be seen today in sights like the Champlain Thrust - a huge slice of rock that broke free of the forming mountains and thrust upwards above rocks that were much younger in age. The Thrust runs along the northeastern shore of Lake Champlain from St. Albans to Burlington.
From the formation of the Green Mountains 400 million years ago until the beginning of the Pleistocene, there is very little record of any geologic activity in the Champlain Basin, this period is known as the Great Hiatus. However, dinosaurs evolved, the mountains around the Champlain Basin continued to erode, and the Atlantic Ocean formed during this time. The only window into the Great Hiatus is the Brandon Lignite, a minuscule deposit of iron-rich clay and a crude form of coal found near Forestdale, Vermont. In this sight, scientists have uncovered the fossils of fruits and plant seeds about 25 million years old. These fossils suggest that, at some time during the Great Hiatus, the climate of the Champlain Basin would have had to have been much warmer. After this warm period, the climate of the earth changed, and the temperature dropped dramatically. It is unclear what caused this change, and the triggers for it could range from changes in air or ocean currents to the positions of the continents.
The Pleistocene or “Ice Age” began about 2.5 million years ago and ended about 10,000 years ago. Glaciers form when the temperature of the earth drops to a point where more snow falls in a given winter than can melt the following summer. When the weight of the overlying snow becomes great enough, the glacier begins to move outwards. At one time the thickness of the glacier in the Champlain Valley was over a mile high. Mastodons and woolly mammoths lived in cold and rugged tundra environments and followed the retreating glaciers northward.
About 20,000 years ago the vice like grip of the Pleistocene began to slacken, and glaciers began to melt. Melt water collected in the Champlain basin, as it was blocked by ice to the north and huge rocky damns of glacial debris to the south, it formed a massive freshwater lake, far deeper that the modern Lake Champlain. The lake covered an area of hundreds of square miles, encompassing both Vermont and New York.
Approximately 13,000 years ago, the glaciers began to melt more vigorously, receding back to expose land that had been covered for thousands of years. The ice that had acted like a dam to Lake Vermont was gone, and the lake level dropped rapidly. The general warming of the climate caused worldwide glacial melt, leading to increased sea levels. Seawater flooded Lake Vermont, replacing it with an arm of the Atlantic Ocean, the Champlain Sea. This large inland bay was connected to the ocean by what is now the St. Lawrence river valley. Scientists have discovered the skeletons of more than a dozen Beluga whales, in addition to the remains and fossils of seals, salmon, herring and mussel shells from this time period.
All are proof that the Champlain Sea was once a fertile and popular extension of the Atlantic. These fossils have been uncovered in New York, Vermont, Ontario and Quebec all of which were encompassed by the Champlain Sea. As the glaciers receded further the earth rose – free of the glaciers crushing weight – causing the Champlain Sea to rise above sea level. Around 9,000 years ago the salt water slowly drained northward from the Champlain Sea, following the St. Lawrence River to the ocean, tributaries and rivers surrounding the basin slowly began to fill the area with fresh water, eventually giving way to the large lake known today as Lake Champlain.
The history of Champlain Valley is complex, extending as far back as the formation of the planet, and contains countless ancient sites and wonders found nowhere else on Earth. A billion years ago the Champlain Valley, along with the entire Earth, was much different than it is at present. The only life on the planet at that time was a wide variety of microscopic plants, bacteria and a few primitive eukaryotes within the ocean, but even then the beginnings of the Champlain Valley were visible in the both the Ieaptus Ocean and the young Adirondacks. Glaciation started about three million years ago and continued to about 12,000 years ago. The glaciers moved from the northwest over the landscape causing rocks and boulders to be dragged beneath the ice. These acted like dams and forced the water in the Champlain Valley to pool in a huge lake – Lake Vermont. At its height, Lake Vermont had a surface elevation around 500 feet higher than Lake Champlain’s current level. As the glaciers melted ocean waters flowed in from the Atlantic forming the Champlain Sea. Massive mountain ranges, deep valleys, saltwater oceans, and towering glaciers; these are not the usual images one thinks of when contemplating the tranquil Champlain Valley. Today this small, and sometimes forgotten region of the northeast is filled with beautiful rolling hills and stocky snow capped mountains, but these hide an absolutely fascinating, and incredibly long story.