What age. An ice age is when Earth

What is an ice age and what factors interact to cause them? This lesson helps answer those questions with the help of graphics and discussion. A lesson summary and brief quiz are also included.

What Is an Ice Age?

To begin this lesson let’s ask the question, what would life have been like in North America 25,000 years ago? Obviously modern amenities wouldn’t be available, but what about the climate? Would it be hot, cold, or somewhere in between? Many scientists agree that it would have been very cold 25,000 years ago because North America was experiencing an ice age. An ice age is when Earth experiences long-term reductions in temperature that results in ice expanding outward from the poles.

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Past Ice Ages

Now that we’ve established what an ice age is, let’s look into when ice ages occur. Notice that I said ages (plural).

That’s because Earth has gone through several different ice ages, with the most recent coming to an end between 10,000 and 15,000 years ago. Ice ages are normal cyclical events driven by a host of various factors such as solar activity, atmospheric composition, ocean currents, Earth’s position in space, and continental movements, to name a few. The interaction between these factors is still the subject of intense study (and debate) by scientists. While we cannot say with 100% certainty when the next ice age will occur, we can say it will definitely happen.

As previously eluded to, ice ages occur periodically. Below is a graph illustrating when Earth’s temperatures dropped and subsequently when ice volume increased (and ice age).

Ice Ages and Global Temperature
Ice Ages and Global Temperature

Turn your attention to the blue or green lines in this graphic. These lines both represent average global temperatures over the past 450 thousand years. Now, notice how these temperatures periodically drop.

The red line more or less parallels the movements of our temperature lines. This red line represents global ice volume. You should be able to see how this ice volume increases to high as average global temperatures decrease. These periods of high ice and low temperatures are ice ages. According to the graphic, Earth has experienced approximately four major ice ages during the past 450 thousand years.

These events would have peaked at around 20, 140, 340, and 440 thousand years ago.It’s worth noting that these are major ice ages. The Earth has experienced several smaller events when ice volumes increased as well.

The point is that ice volume fluctuates between periods of high ice volume and low ice volume. Today, Earth is experiencing a period of low ice volume, but that’s happened several times before. In each case, the ice has returned fairly rapidly. So, if our graphic lines are projected outward into the future, we can predict the coming of another ice age. When exactly? Scientists cannot be sure, but they do know the ice will be back.

Lesson Summary

Earth is currently experiencing a period of relative warmth and stability. However, this will likely change at some point in the future.

That’s because Earth will experience another ice age. An ice age is when ice expands outward from the poles due to long-term reductions in global temperature. Ice ages have occurred throughout Earth’s history with the last one ending between 10,000 and 15,000 years ago. The causes of ice ages are complex and still under investigation.

However, the interactions between solar activity, atmospheric composition, ocean currents, Earth’s position in space, and continental movements are likely the driving forces.


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