How the Earth was Made - Season 2

Mt Vesuvius is the world's most dangerous volcano, and it threatens three million people. It was responsible for the most famous natural disaster of ancient history.

Four and a half billion years ago the Earth formed from dust in space to become a molten ball of rock orbiting the Sun. This episode travels back in time to investigate how the fledgling planet survived a cataclysmic cosmic collision with another world.

Africa's Sahara Desert is the size of the United States, making it the largest desert in the world. It's also the hottest place on the planet.

The Sierra Nevada, North America's highest mountain range, contains one of the most awe-inspiring geological features on the planet: Yosemite Valley. Walled by sheer 3,000-foot granite cliffs and made from one of the toughest rocks on earth.

From Alaska to New Mexico, the Rockies are one of the great mountain belts of the world--caused by tectonic forces of the Pacific Plate pushing against the North American continent.

The single longest linear feature on Earth--the "Ring of Fire" circles almost the entire Pacific. It is a ring of active volcanoes.

It is the tallest and biggest mountain on earth, as far removed from sea level as it's possible to be--and yet its sedimentary layers contain fossils that were once creatures that lived on the ocean seabed.

It is not only a place of natural splendor but a geologic treasure trove as well. Hidden in the sediments of the rocks in its walls is evidence of the coldest time on our planet--ironic in one of the hottest places on Earth.

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?