Glaciers We wouldn’t be here without them.

A Glacier is an accumulation of snow that is large enough to survive the summer melt. These large ice masses begin to move down hill by gravity. It can move several centimeters to several meters a year depending on its size. These glaciers will settle into lower lying areas as they move.

The two types of glaciers we will talk about are Alpine Glaciers and Continental Glaciers. I. Alpine Glaciers-are found in the mountains. They carve out U- shaped valleys as they move.

Glaciers meet water.

Icebergs are large pieces of glacier that break off into the water.

U-Shaped Valley

II. Continental Glaciers-also known as ice sheets. These large sheets can cover thousands of square miles and are responsible for most of the features we see in New York State and Long Island.

Once any type of glacier moves over the landscape, it leaves behind a path of deeply scratches rocks. These scratches called striations are caused by rocks already suspended in the glacier scratching the ground rock by abrasion.

Striations

As glaciers advance they remove material from the landscape. This material must be deposited somewhere. The glaciers drop unsorted material called till into piles. Then the glacier advances over them. These piles are called Drumlins.

Drumlins

Another depositional feature is called a Moraine. A moraine is a pile of unsorted till found at the terminal end of a glacier. Moraines can also form in the middle of an advancing glacier. The glacier gets the material as it erodes the landscape as it passes.

Glaciers pick up a lot of material along the way.

As the ice passes it rips out large portions of the ground. When the ice melts, these holes fill with water. These are called Kettle Lakes. Lake Ronkonkoma is a kettle lake.

The ice sheet advanced to the where the middle of Long Island is today. The middle of Long Island is where you will find the Moraines. All areas south are called outwash plains (flood plains). These are areas where the landscape is flat and the area is fine sediment. There are very few natural, large boulders.

This sandy, silty, milky looking water is called outwash. This material formed the land we live on today.

Outwash Plain

Remember we said the glaciers deposit material in unsorted piles. This is because all different size particles can be carried by a glacier. Every once in a while we find large boulders that don’t fit in with the surrounding material. These are called Erratics.

Glacial erratics do not match the surrounding bedrock.

Here is the whole picture all together.

Why can’t you find any glaciers in New York State today? The ice and snow all melts during the summer. What is the difference between transported soil and residual soil? Transported soil was deposited by an agent of erosion. What is a glacial erratic and why are they not found around here? A glacial erratic is a larger boulder left behind by a glacier that does not match the surrounding bedrock. You don’t find them around here because we are located on an outwash plain and the meltwater was not strong enough the carry the large rocks.