Tag Archives: Glaciations

Get out Your Ice Skates ‘Cuz We’re in an Ice Age

It might not look like it when you look out the window, but we’re in the middle of an ice age. Just because the upper half of North America isn’t covered by a mile and a half to two and a half miles of cruising glaciers doesn’t mean they won’t come back.

Our current ice age started about two and a half million years ago, give or take a couple three tens of millennia. The last glaciation started about a hundred and ten thousand years ago and ended about twelve thousand years ago. It hit a maximum of ice coverage of North America about twenty six thousand years ago. Glaciations last about a hundred thousand years and inter-glacial periods between ten thousand and fifty thousand years, depending. We’re past the ten thousand year mark. The ice sheets could start cruising back anytime now.

What does the timing of ice ages depend on, you might well ask? Depending, mainly, on where we are in a Milankovitch cycle. What the hell’s a Milankovitch cycle, you might well ask?

Ah, good old Mulutin Milankovitch, the well known Serbian geophysicist and astronomer. Back in the 1920’s, he took all the known data about the earth’s orbit, how it varies from nearly a circle to slightly elliptical, how that orbit also wobbles up and down like a spinning coin at the end of its spin, and the fact that, as the earth spins about its axis, that axis also wobbles about a bit. He took all that and figured out that, since all this affects how much sunlight hits the continents during the changing seasons, that the effect was that, when the axial tilt was steepest, and the earth’s orbit was most elliptical, we got colder. Earth is known to have had 5 serious ices ages in its four billion plus year history. A couple of them made earth resemble the ice planet Hoth, except for some areas around the equator. No fossil tauntauns have been discovered as of yet.

Milankovitch’s theory matched what was known about ice ages back in the 1920’s, more or less. These days it has been modified by throwing in continental drift, which was merely an unproven hypothesis back when he was hypothesizing away. Where the continents are affects ocean currents, which affects the distribution of heat around the planet, etc, etc, etc.

There’s a moving image for you: continents scooting around, the planet wobbling on its axis while whipping around the sun, orbit stretching back and forth while wobbling up and down. Throw in the fact that the whole solar system bobs up and down across our galaxy’s equator while orbiting around the galaxy. Makes you wonder why we aren’t all nauseated.

Maybe that’s why there are volcanoes. Our mother earth, good old Gaia, gets spin dizzy and just needs to barf occasionally.

First shared on the Squatcher’s Lounge Podcast:

For the reading impaired, an audio version of this quasi theory may be found here: