Glacial Change Documented

Glacial Change Documented

Glaciers... Defined

Although ice is generally thought of as rigid and immobile, glaciers are not stationary masses. In fact, in order to be considered a glacier, an ice mass must be of sufficient size and thickness to flow. Its sheer weight becomes so great that gravity forces the ice mass to spread outward and downslope.

Poll

So... Do you think that Illinois had glaciers?

• Yes

• No

It Did!

If you look closely at the map of North America, you can see how the ice sheets and glaciers made their way down into Illinois

How do Glaciers move?

Mass Balance

A glacier moves according to its mass balance—the difference between how much snow and ice it gains each year relative to how much it loses.

Calculating Mass Balance

When the amount of snow and ice accumulated on a glacier through precipitation or wind deposits exceeds the amount lost due to melting, wind erosion, or breaking off into the sea, it is said to have a positive mass balance year.

During extended warm periods, when the snow and ice lost over a year exceed what is gained, the mass balance is negative.

Poll

In which season would you expect the mass balance have the MOST NEGATIVE balance (the glacier lost the most mass)

• Winter

• Spring

• Summer

• Fall

Open Ended

Explain why you chose the season in the previous question.

Movement

Glacial movement plays an important role in shaping landscapes. In mountainous regions, glacial erosion widens and deepens a V-shaped river valley that guides a glacier's flow.

When the ice thaws, a U-shaped valley is revealed. Stray boulders that have been deposited far from their source, known as glacial erratics, often litter this transformed landscape.

Deep grooves, or striations, in exposed bedrock are other telltale signs of glacial movement.

Since 1900, most glaciers around the world have been retreating and continue to retreat as global temperatures rise. The loss of ice could lead to potentially serious consequences for humans.

Open Ended

Explain how the loss of ice (melting of the glaciers) could adversely, badly affect humans.

Accelerated melting of valley glaciers could produce catastrophic flooding followed by long-term drought, which would affect hundreds of millions of people who rely on stable glaciers to provide water for agriculture and their drinking supply.