What caused, and thawed, the last Ice Age?

Question

What caused, and thawed, the last Ice Age?

Answer 1

We are still in the Ice Age.

For most of it's existence the Earth has been without ice, indeed that is it's normal state.

We believe that the Ice is normal because all of our existence (200,000 years approx) has been governed by ice.

The last cause of this Ice Age was the continental drift disrupting the warming oceanic currents (South America bumping up against North America).

Periodically the Earth moves on an elliptical orbit around the Sun, this allows some cooling at the poles.

Periodically too the trapped carbon di-oxide in rocks is freed by natural action (volcanic).

So the warming and cooling is natural, warming is the norm.

We, in our wisdom have accelerated the process by producing an abundance of greenhouse gases, but then again the Dinosaurs produced a massive amount of Green house gases too in the form of methane.

The implication is of course that we are no cleverer than Dinosaurs.

Any help?.

Answer 2

Still some questions about all that, actually.  There are cycles in climate that are associated with the earth's orbital behavior and the sun's output that seem to explain some of the general cycles during the "ice age".  Apparently, the global cooling was also produced by the uplft of the himalayas and the closing of the atlantic-pacific ocean link in central america (these changes altered air and ocean currents and heat transfer across the globe).  Many causes, no simple answers.  Complex problem.

Answer 3

The natural cooling and heating of the planet. And nobody even drove 4X4s then!

Answer 4

Nature,

Similar weather changes like we are getting these past few weeks, The world has to heat up (people think that that is global warming but i think global warming is the biggest load of p**p) before it cools down into an ice age.

Answer 5

The earth goes through many cycles some over tens of years others over millions of years. Ice ages are part of this. The last one was just part of one of these cycles. As for what exactly caused it no one knows for sure.

Answer 6

Cold, and then heat!

Answer 7

Its a very big question.

First we are still in an ice age and have been for about 2 million years.  Ice ages are divided into glacial and interglacial periods where ice fronts advance and decay.  The Earth is currently in an interglacial. The last glacial period started about 80 thousand years ago, the last interglacial started about ten thousand years ago and a new glacial will start sometime in the future.

Its very rare for this planet to have ice at the poles.  Normally its a tropical water world.  It is even rarer to have ice at both poles.  

A cycle that may have influenced the current ice age is the movement of the continents across the equator to block a warm current that for many millions of years ran around the equator.  This current may have kept both poles warm as well as most of the planet tropical.  

Other factors that may have cooled the planet are the isolation of Antarctica, the growth of the Tibetan plateau and a net drop in global carbon dioxide over the last 70 million years.

As the planet is in a cooler phase the Earths orbital cycles (The Malankovich Cycles) can drive the plant between glacial and interglacial.  They do not cause the ice-ages but they do influence the the changes between advancing and retreating ice by changes in the shape of the Earth orbit and its angle of tilt towards the Sun.

There are possibly many other factors such as the Earth albedo (its ability to reflect energy back into space, so more ice more energy reflected back) and solar energy cycles that need also to be considered as well as factors that we do not currently understand or even know of.

So what caused it...we don't really know the full story yet but bit by bit science is unraveling this problem because one day the ice will return and if we are still here we will have to learn to live with it.