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Farmers Almanac
The 2016 Farmers Almanac
Farmers' Almanac

Ask Caleb: What Causes an Ice Age?

Ask Caleb: What Causes an Ice Age?

“What caused the ice age?”
-David Sutherland

There have actually been numerous ice ages throughout the history of the Earth. An ice age occurs when thick sheets of ice build up over much of the surface of the Earth in a process called glaciation. There are still places on the Earth where ice sheets cover the landscape year-round, most notably in Antarctica and Greenland. During a glacial period — informally known as an ice age — these ice sheets grow over the course of many thousands of years, until they cover much of the land and sea.

No one knows for certain what actually causes this to happen, though scientists have many theories. Most agree that ice ages are caused by a combination of factors, including the precession of the Earth’s equinoxes (its “wobbly axis”), volcanic activity, the movement of tectonic plates, sunspot activity, and the amount of greenhouse gases (such as water vapor, carbon dioxide, methane, nitrous oxide, ozone, and chlorofluorocarbons) in the atmosphere. Any of these factors can affect the amount of sunlight that reaches the Earth, or escapes its atmosphere, preventing ice sheets from melting.

The more ice that covers the face of the Earth, the harder it is for the Sun to melt it. Large sheets of ice reflect much of the Sun’s light and heat away from the ground and back into the atmosphere.

At one point in time, hundreds of millions of years ago, the entire face of the Earth, including the Equator, may have been completely encased in ice. Scientists call this theory, “snowball Earth.” Most ice ages aren’t quite that extreme, and may affect only one hemisphere or the other, rather than both at the same time.

The last major period of glaciation ended between 15,000 and 20,000 years ago.


1 Sheri { 03.08.11 at 3:44 pm }

Warming and cooling of the earth is so fascinating. Overall I am aware of extremes where there were none when I was younger.
My neighborhood has chosen to not asphalt our streets, our area is always pointed out as the coolest in the summer, coincidence?

2 Steve { 03.05.11 at 10:07 am }

If you want to know when the next mini ice age is starting go to this web site:
It appears to be already starting…Keep warm…

3 arvin smith { 03.02.11 at 7:21 pm }


4 Carol { 03.02.11 at 3:32 pm }

Hi Jamie,
My point was the fact that we have warming and cooling and then warming. Though, I guess it’s understood by our savvy Farmers Almanac readers the warming and cooling is cyclical. Thanks for the comment. Hope you have the opportunity to read the book I cited in my comment. Very interesting.

5 Jaime McLeod { 03.02.11 at 1:45 pm }

Hi Carol,
We wrote about the Little Ice Age here. it wasn’t included in this article because it wasn’t an official ice age, in the technical sense.

6 Carol { 03.02.11 at 12:18 pm }

I had hoped the Little Ice Age between 1400 and 1800 that was followed by the MWP (Medieval Warm Period) had been addressed in this article. Warming and cooling (glaciation) have been occurring for many centuries if not the entire life of this planet. During that time there was no industrial era with the resultant CO2, no coal being used with it’s pollution, no CO2 emissions from the transportation industry, and on and on.

A recent book from the CATO Institute titled, “The False Promise of Green Energy,” is a must read for anyone interested in understanding how the Green Movement is built on a fallacy. The Green Movement is not workable and will created massive debt and the standard of living for everyone will be seriously compromised. One example explained early in the book states the pursuit of ethanol as a fuel will require major construction of parallel pipelines and storage tanks because it is highly corrosive. This would be a boon for automotive mechanics who will be regularly rebuilding engines in cars if fueled by ethanol and repaired frozen fuel lines. Ethanol freezes at a fahrenheit temperature of between 32 t0 40 degrees. animal biodiesels Gel at even higher temps. The book is authored by four experts, Andrew P. Morriss, Wm. T. Bogart, Andrew Dorchak and Roger Meiners. Their credentials are enumerated at the end of the index. This book is very readable and comes with graphs and charts illustrating the text. Very well done.

7 Frank Maddox { 03.02.11 at 10:43 am }

Since an “Ice Age” would seem to perpetuate itself; and there is no concrete explanation as to the beginning or end of one. Could the concept be a fallicy? I submit this to you: As we know the tectonic plates move, and as we know the poles shift, maybe the land shifted to where the cold/ice was instead of the cold and ice coming to where the land was.

8 Adam FreeMan { 03.02.11 at 10:02 am }

“Snowball Earth” is a perfect description of the Earth in Genesis before YAHWEH started HIS work. The theories of Global warming and Global freezing are political tools that use the natural ebb and flow of the sun’s and Earth’s actions in order to enrich and enpower the elite.

9 Lynn Bushard { 03.02.11 at 9:51 am }

Why the fuss about global warming ? It has been going on for centuries

10 Tina Gallagher { 03.02.11 at 9:46 am }

I would like to have seen in the article information regarding how often these ice ages occur, and which parts of the Earth seem to be targeted. Thank you for an informative article, nontheless.

11 Fred & Vera Richardson { 03.02.11 at 9:04 am }

I was pleased to read this report on ice ages. I live in a part of the country, (The Ozarks), where the concept that the earth is more than 6,000 years old is considered heretical and reports such as this based on scientific facts is always like a breath of fresh air.

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