Geological Evidence of Glacial Activity in New York State

The ice age in North America began about two million years ago and ended about 6000 years ago. During this period four major glacial advances occurred. Deposits and glacial evidence may be found in all northern states. But only in New York can we find the latest glacial evidence. Earlier glacial evidence has bin swept away. This glacier that swept away all the evidence is called the Wisconsin glacier. This took place 20,000 years ago. Many examples of evidence of this glacier are visible today. n years ago and ended about 6000 years ago.

GLACIER FACTS 20,000 years ago glaciers covered all of Canada and extended southward over the sites of Seattle, Chicago, and New York city. All of New York ,except for the Allegheny state park was once buried under ice more than one mile thick. The glaciers over road all of the Adirondack mountains including the highest mountain which is Mt. Marcy. Because of their great thickness and mass, glaciers completely override all land features even some times large mountains.

Today very few places have low enough average temperatures and sufficient snow fall for glaciers to form. Antarctica is covered by the largest glacier that is one and a half times as large as the United States. New York’s Finger Lakes were carved out by glacial ice. Long Island is a 120 mile long out washed plain. It has no bedrock. Niagara Falls began when the Wisconsin Glacier melted.

GLACIER TERMINOLOGY Glacier: is a body of ice showing evidence of movement as reported by the presence of ice flow line, crevasses and recent geologic features. Glacial Advances: is the net movement of glacier terminus downvalley. Advance occurs when the rate of glacier flow downvalley is greater than its rate of ablation. Moraine:rock debris deposited by a glacier. Striations: are the scratches etched in to the rock at the bed of a glacier. Till:is the unsorted rock debris deposited directly by the glacier without the extreme reworking by meltwater. Also called Glacial Till.

Erratic:Bolder transported by a glacier that generally differs from the bedrock beneath the rock. Kettle: depression in a glacial deposit were outwash was deposited around a residual block of ice. Kame: A conical hill of sand and gravel deposited by a melting glacier. Continental Glacier: ice sheet of continental proportion. MeltWater: water from ice and snow, especially from a glacier

This is a glacial erratic that shows evidence of weathering and erosion

Two erratics lined up in approximate direction of ice flow

May be a small kettle lake or pond, rounded edges and poor drainage.

A large erratic placed here by a glacier.

Evidence of frost wedging since glacial deposition.

One side of this U-shaped glacial valley shows glacial debris of all sizes

U-shaped valley showing smooth side to the right.

Unsorted, angular edged fragments deposited by glacial ice.

Young stream eroding through the glacial debris.

Scratches on a rock caused by glacial till

Another large erratic showing scratching going in one direction.

Evidence of weathering of erratic since the last ice age.

A different angle of this large glacial erratic

Large erratic for this area but in the mid-west the ‘haystack boulders’ may be as large as a house.

Bibliography Ramsey, William L. Modern Earth Science. Holt, Rinehart and Winston Publishers: NewYork, 1979. USGS. “Glossary of Selected Glacier Terminology”. http://vulcan.wr.usgs.gov/glossary/Glaciers/glaciers_terminology.html Van Diver, Bradford B. Roadside Geology. Mountain Press Publishing Company: Missoula, 1985.