MOHAWK - Discovering the Valley of the Crystals Copyright 2002
What Created the Mohawk Valley
To really appreciate the Mohawk Valley it's essential to understand how it came to be.
I've read dozens of books describing the geology of upstate New York, and I've traveled the length and breadth of the Mohawk Valley trying to visualize the forces of nature that created this unique passage through a chain of mountains. It took awhile but I got it, and with the help of friends who have little interest in geology or what went on here thousands of years ago, I think I can help you get it too.
So, with the aid of your imagination and a shaded relief map, I offer the following:
Picture this. From Little Falls west is a huge lake, many times bigger than Lake Ontario, that covers all but the highest peaks. From The Noses east is another huge lake, many times bigger than Lake Champlain. At Little Falls is a ridge of solid rock. Not just any rock, but super-hard Adirondack rock that had pushed up through overlying dolostone and shale when the Adirondack dome started to rise 100 million years ago. Further east, in the area of The Noses, is also solid rock, part of a chain of mountains that run from Maine to Georgia--- the Appalachian Plateaus. In between is glacial till--- boulders, rocks, gravel and sand--- packed high and hard by a mile-high glacier.
That's how it was after the last glacier melted 10,000 years ago.
For a few thousand years the huge lake to the west, now called Glacial Lake Iroquois, put enormous pressure on the solid rock and glacial debris dam at what is now Little Falls. As the dam deteriorated, the lake started to overflow, creating falls, rapids and a river of such proportions they are beyond imagination. Their force was so great that swirling water and chunks of glacier-deposited rocks and sand literally ground holes in the underlying dolostone, creating huge potholes. Take a look.
For eons the huge lake's outlet eroded a 25-mile channel through solid rock and glacial till, breaching the Appalachian Plateau at The Noses and pouring into Glacial Lake Albany.
Can't picture it? Look at this shaded relief map of the Mohawk Valley. Follow the outline of Lake Iroquois. Look at the narrow gaps at Little Falls and the Noses. See the Lake Albany basin.
Got it? If that's all you get out of this chapter you are ahead of the game. However, there is much, much more. And it's fascinating......
....... if you have time and imagination.
Water, Water, Everywhere Water
Five hundred million years ago a vast, shallow ocean covered what is now New York State. To the west a high plateau, to the east a range of towering mountains --- rivaling the Himalayas of today --- eroded into the ocean. For millions of years suspended particles of eroded rock and dissolved minerals settled to the ocean floor. Over time, the pressure and heat caused by the weight of overlying sediment, turned sand to sandstone and carbonate minerals to dolostone and limestone. These layers of sedimentary rock covered ancient granite-type rock.
For 50 million years oceans and landmasses rose and fell, and primitive creatures populated and evolved on the ocean floor. Brachiapods (clam-like), cephlapods (octopus-like), bryazoans (moss-like), crinoids (single-stem plant-like) and trilobites (horseshoe crab-like) lived, died and became part of the calcium-rich sediment that eventually turned to limestone laced with the fossils of these ancient life-forms.
Under the ocean floor, salty seawater, laden with dissolved silicates, dripped, trickled and percolated through layers of dolostone to find cavities created by gas pockets. Under extreme heat --- duplicated in laboratories today --- dissolved silicates formed quartz which, depending on impurities and temperature, became chert or double terminated quartz crystals.
Some 450 million years ago calcium-rich deposits dominated ocean sediments, however, intermittent inflows of mud eroded from the eastern mountains also settled to the ocean floor, eventually forming thin layers of shale intermixed with thick layers of limestone. Ten million years later mud from the eastern mountains poured into the ocean basin to become deep deposits of shale.
The Appalachian Plateau
Around 330 million years ago two huge continents (proto-North America and proto-Africa) collided, causing an uplifting of the compacted sediments that once lay horizontal on the ocean floor. This uplifting continued for more than 100 million years, causing heat and pressures that altered the composition and shape of the sedimentary rock, sometimes folding, faulting or turning it on end. Today this much eroded and often faulted Appalachian Plateau is a chain of mountains that runs from Canada to Georgia, crossing New York State north to south, and once crossing the Mohawk Valley between Little Falls and The Noses.
Young Mountains From Old Rock --- Still Growing
Around 100 million years ago a hotspot formed in the earth's crust under what is now northeastern New York. This extreme heat changed the composition of the "old rock" and caused it to expand upward, creating the Adirondack Dome.
Sandstone and other sedimentary rock covered the Dome as it moved slowly skyward. Millions of years of erosion stripped these softer rocks from the mountains and exposed the harder metamorphic --- granite-gneiss --- rocks that erode more slowly. At lower elevations, sedimentary rocks such as sandstone, dolostone, limestone and shale were pushed upward, causing all these rock formations to angle down and away from the mountains.
The upward movement of the Adirondacks continues today at the rate of 2-3 mm a year. Fact is the Adirondack Mountains are growing 30 times faster than the wind, rain, ice and snow are wearing them away.
Intrusions of Adirondack rock also occurred at a few lower elevation areas such as the outcrops near Middleville and at Little Falls.
Mile High Glaciers, Ancient Lakes and Mighty Rivers Sculpted the Land
The ice age in upstate New York began 1.6 million years ago and ended a mere 10,000 years ago. Advancing and retreating glaciers, ancient lakes and mighty rivers sculptured the land, left enormous deposits of rock, gravel, sand, silt and clay . . . and created the Mohawk Valley.
Glaciers more than a mile high covered this part of the state, leaving scars on the highest Adirondack peaks. As these monstrous fields of ice moved south they tore Adirondack rocks from the peaks. Some of these rocks were suspended in the ice, to be deposited miles away when the ice melted. Most became part of a massive grinding and conveying system. The weight of the ice and the abrasiveness of "sandpaper" rocks imbedded in the bottom of the glacier, ground boulders to rocks, rocks to pebbles and pebbles to sand .... and carried them southward. When glaciers encountered softer sedimentary rock such as shale, limestone, dolostone and sandstone, they were ground to rocks, pebbles, sand, silt and clay.
Some 12,000 years ago when the glaciers started to melt, suspended boulders (erratics) --- some 20-feet across and weighing 100 tons --- and all those grades of ground-up rock were deposited throughout New York State. At the southern terminal of some of these receding glaciers, vast amounts of mixed rock, gravel, sand, silt and clay --- glacial till --- were deposited. These moraines created hills, ridges, valleys, kettle holes and lakes, and changed the direction of rivers. One of these moraines changed the direction of West Canada Valley. Prior to the ice age, the river flowed southwest past the present village of Prospect, on to Holland Patent, along the path of Nine Mile Creek and entered the Mohawk River west of Marcy. Glacial till deposited in the Prospect area, blocked the stream's original path and redirected it southeast through Trenton Gorge. (Outflows from ancient glacial lakes had already started the formation of Trenton Gorge when the river's direction changed.)
Glacier Melt-Waters Create Trenton Gorge,Trenton Falls and Boonville Gorge
As glaciers melted and receded northward, ice dams, glacier deposits and rock formations held back vast areas of freshwater. These ancient lakes existed for thousands of years and covered much of upstate New York. A glacial lake in what is now the upper Mohawk Valley was so big and deep that it filled the entire valley west of Little Falls and most of West Canada Valley. The Hasenclever and Deerfield hills between West Canada Valley and the Mohawk Valley were islands in that lake.
For a time one of the outflows from this lake ran northwest through a gap near present day Trenton Falls. Vast amounts of fast moving water, rocks and sand, passing through this gap into a northern basin, cut into the limestone in this area and started the creation of Trenton Gorge. Waterflow through the gorge was later reversed when the southern lake dropped in level and the water level in the northern basin ---- in the Forestport area --- increased. For thousands of years enormous volumes of water, rock and sand passed through this outflow, deepening the gorge. Water activity and ice caused joints (deep cracks) in the limestone to widen, causing huge sections to break loose, resulting in step-like formations topped with resistant limestone, creating a series of magnificent waterfalls now known as Trenton Falls.
Trenton Gorge and Trenton Falls (Kuyahoora) were created by glacial water. This is a view of Upper High Falls with Mill Dam Falls in the background.
Prospect Falls does not appear to be one of the Trenton Falls. It's more likely a side of the gorge that was cut by a glacial outflow. The other side was cut away by subsequent stream erosion and/or hidden under glacial till.
Other outflows of this northern lake determined the course of a number of Mohawk Valley streams. A section of the river between North Branch and Hillside, sometimes known as The Canyon, was created by this glacial lake outflow, as was the steep-sided Boonville Gorge and its waterfalls. The Lansingkill now follows the path of this ancient river. An outflow also ran through present day Remsen and Barneveld cutting through limestone, creating waterfalls and determining the course of Cincinnati Creek. Another created Steuben Valley and set the path of Steuben Creek.
The Canyon between West Branch and Hillside was created by a glacial river.
Glacial meltwaters also created Frankfort Gorge, Ilion Gorge, and the ravines, waterfalls and potholes on most of the streams in the Mohawk Valley. Of course the greatest waterfalls and potholes were at Little Falls.
A section of the Mohawk Valley, a Mohawk Castle, a British Fort, a village and a creek were named after a pothole located in Canajoharie. This pothole was famous long before the written word reached the valley. Canajoharie describes "the pot that cleans itself."
Glacial Till Sorted By Lakes and Rivers
Glacial river and lake-waters sorted glacial till. Rivers and streams running into the lake carried rocks, gravel, sand, silt and clay. The finer and lighter particles of clay were carried out into the lake and settled to the bottom as clay deposits. Silt settled out of the water closer to shore. Sand, gravel and rocks built up as deltas near the mouths of rivers and streams. When these lakes and rivers reduced in size, sorting continued, often depositing sand over clay, and gravel over sand.
How Big Were They ?
It's difficult to comprehend the size and depth of the glaciers and the glacial rivers and lakes that covered this area. It helps to consider that the hills that start just north of Fairchild Road in Remsen and continue south to Prospect and Hinckley, consist of rock, gravel and sand deposited by a glacier. In addition to separating the glacial lakes in this area and changing the flow of West Canada Creek, as noted earlier, this glacial moraine contains a number of "kettle holes". These conical-shaped holes, hundreds of feet across and dozens of feet deep, were created when glacial ice, imbedded in the moraine, melted. The melt-water drained through the till; gravity and erosion did the rest. Similar deposits can be found in many areas of the Mohawk Valley.
Stand atop Deerfield Hill or Frankfort Hill or any hill in the upper valley that is over 1300 feet above sea level. Consider that all but these highest hills were covered by a glacial lake. Look more closely at the lay of the land to see the terracing created when the lake dropped to a lower level, remained there for many years, and then dropped again and again as the downstream dam of ice and debris eroded away.
Look at the hills on both sides of Boonville Gorge. When the glacial lake to the north drained through this area, the glacial river was as high as these hills. The volume of water and the amount of rock, gravel and sand it carried was so great it created the gorge and deposited millions and millions of tons of gravel and sand in the lower valley. These deposits created a huge delta north of Rome. The Village of Delta was built on that glacial river deposit. Today much of this ancient delta is covered by Lake Delta. Further downstream this glacial river deposited the sand that became the Rome Sand Plains.
Sand plains of various sizes were created by glacial river deposits. These sand "deltas" became sand plains when the water receded and the dry sand was spread by prevailing winds. There are sand plains in the Town of Trenton and the Town of Norway. The largest sand plain in the Mohawk Valley was created between Schenectady and Albany by the outflow of Glacial Lake Iroquois.
Adirondack Rock More Resistant to Erosion
While glacial lakes and rivers had a major impact on the lay of the land and the direction of streams in the lower valley, it had far less impact on the terrain of the Adirondack stretches of such tributaries as West Canada Creek and East Canada Creek Although these mountain valleys were widened and sculpted by the glacier, Adirondack rock --- mostly granite-gneiss --- resisted glacial and glacial water erosion. The glacier, however, tore boulders and rocks from the mountains, suspended some of them in ice, or ground them to rocks, pebbles and sand. When the glacier melted the larger rocks and boulders settled on mountain tops and ridges, and in the valley. The rest were washed downstream.
Glacial meltwater and debris that plummeted down waterfalls and through crevices in the Adirondack rock, dug small lakes, ponds and potholes in solid rock. Most of the lakes and ponds in these upper valleys and many of the deeper water areas in the tributary streams were created or started at that time
The potholes in the rock outcrop in West Canada Creek, three miles northwest of Nobleboro are examples of the grinding power of volumes of water swirling small rocks, gravel and sand. In this case it was --- and still is --- Adirondack rock grinding Adirondack rock that created these unusually large granite-gneiss potholes. The West Canada's Ohio Gorge was created when an upheaval of granite-gneiss fractured. Repetitive thawing and freezing widened fractures, breaking off huge chunks of rock. Glaciers and glacial water carried away debris and further sculpted the half-mile long gorge.
What Was Left After It Was All Over?
When the ice age ended and the glacial lakes and rivers had all but disappeared, the Mohawk Valley consisted of rock and ground-up rock. In the mountains thousands of acres of solid granite-rock, huge boulders, piles of rocks and sand dominated the landscape. In the lower valley dolostone, limestone, shale, and sandstone with a couple of intrusions of Adirondack rock was covered in most areas with mixed and sorted deposits of rock, gravel, sand, silt and clay. In many areas hillsides and valleys were littered with Adirondack rocks of many sizes, some as large as small buildings.
The stage was set for life to return to the Mohawk Valley.
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