The Effect of Ice Age Glaciers: Formation of Pluvial Lakes

Lesson Transcript
Instructor: Rebecca Gillaspy

Dr. Gillaspy has taught health science at University of Phoenix and Ashford University and has a degree from Palmer College of Chiropractic.

An ice age is a prolonged period of time where cold weather and large glaciers cover most of the earth, and when these glaciers melt they can cause major changes to the environment. Lean more about glaciers, their erosion and deposition process, how pluvial lakes are formed, and what effects this has on the planet. Updated: 10/04/2021

Ice Ages

If you live in an area where winter roars its ugly head and plummets temperatures below zero, then you know the joy that comes with the arrival of spring and warm temperatures. But, what if the weatherman said spring wasn't scheduled for another 10 million years? Well, if that were the case, then you would be living in an ice age and be able to look forward to nothing but a prolonged period of cold with glaciers blanketing much of the earth.

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  • 0:01 Ice Ages
  • 0:27 Glacial Erosion and Deposition
  • 2:48 Pluvial Lakes
  • 3:52 Isostatic Depression
  • 4:42 Changes in Sea Level
  • 5:29 Lesson Summary
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Glacial Erosion and Deposition

Glaciers are huge moving mountains of ice that can directly affect the landscape in many ways. The carving and shaping of the land beneath a moving glacier is a process referred to as glacial erosion. As a glacier moves over the earth's surface, it plucks up rocks and sediment, which then get stuck to its belly and go along for the ride. These particles act like sandpaper and scratch the bedrock below. The removal or rocks and grinding of bedrock create entirely new landscapes.

Glacial erosion is responsible for some of the most stunning rock features in mountainous regions, such as glacial horns, with their sharp, angular peaks, and cirques that have round hollows with steep sides.

Glaciers carved out basins within bedrock that later filled with water, forming millions of lakes that exist to this day. Glaciers were responsible for turning many of the typical V-shaped valleys between the mountains into U-shaped valleys with broad and wide valley floors.

When the environment emerges from the freezing ice age temperatures, we see another direct effect, or glaciers known as glacial deposition, which is the settling of sediments left behind by a moving glacier. This process occurs as the melting glaciers drop all of the rocks and sediments they previously picked up. It's almost as if the ice age glaciers were the original litter bugs of the environment, because they spread debris over vast areas. The unsorted materials moved and deposited by a glacier is known as till.

Till can be pushed or deposited into piles. Lines of till that form at the edges of past glaciers leave behind landforms known as moraines. Moraines form in lines and give a general idea of the boundaries and farthest point that the past glacier reached.

We also see drumlins, which are elongated hills composed of glacial till. A number of drumlins can form together in a field, and their unique shape makes them look almost like the backs of whales breaching the surface of the ocean. Glacial erosion and deposition are direct effects of ice age glaciers, but there are also indirect effects that impact the earth.

Pluvial Lakes

One indirect effect is the creation of pluvial lakes, which are lakes that were at one time very large due to excessive rainfall associated with glaciation. To recall this term it might help you to understand that the word 'pluvial' means rain in Latin. So pluvial lakes formed due to very heavy rainfall, but there's a catch - pluvial lakes formed in desert areas.

Are you wondering how so much rain fell in the desert? Well, it all had to do with the presence of ice-age glaciers. Glaciers are huge, and during an ice age they can cover about a third of the land. These huge ice cubes changed air flows and weather patterns and turned previously dry areas into wet areas. This allowed basins in these previously dry areas to fill with water, giving us the pluvial lakes. After the ice age, the pluvial lakes began to shrink, but we still see some remaining today, such as the Great Salt Lake in Utah.

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