How the Earth Was Made

Over 20 years ago, Mt. St Helens--thought to be dormant--shocked America when it exploded. It is an acidic volcano--the magma beneath is full of volatiles making it highly explosive. A new plug has formed in its throat and is rising. When it blows it will be like uncorking a champagne bottle, releasing pressure below and allowing dissolved gases to escape and explode. The question is...when will it blow again?

In the remote wastes of Siberia buried under snow are the remains of one of the greatest catastrophes that the Earth has endured. 250 million years ago, huge volumes of lava spewed out onto the surface--so much that it would have buried the whole of Texas under one mile of lava. At first the temperature dipped but then the greenhouse gases that escaped from the depressurized lava caused a massive global warming. It wreaked havoc and 95% of the species on Earth became extinct. Yet life hung on and in time this disaster paved the way for the next great phase of life on earth--the age of the dinosaurs.

Why do we have ice ages and when is the next one due? Chart the progress of different ice ages through the history of our planet, from Snowball Earth hundreds of millions of years ago to the recent ice ages. As the Earth circles the sun, its orbit changes slightly and so does it angle of rotation. When the right wobble in our rotation combines with the right orbit, the Earth is, and will again be, plunged into an ice age--but maybe not for a few thousand years.

Gold dates from the time of the supernova explosion that gave birth to the building blocks of our solar system. When it was created, the Earth included a tiny percentage of gold atoms, and over the aeons geologic processes have concentrated it into various nooks and crannies around the globe. The best of it is in the ancient Precambrian rocks in South Africa, where the deepest mines in the world extract it. In other regions of the world, gold can be gathered from younger sedimentary rocks that have been eroded off older Precambrian rocks. The American gold rush was this type of deposit. Now in Nevada, sedimentary rocks are leached on a truly vast scale to extract the gold.