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Volcano
Category All Natural World
Series Title Earth - The Power of the Planet
Episode 1
Duration 50 mins
Product Code 22072
Broadcast Year 2008
Price £195.00

Volcanoes are usually seen as destructive, but in this BBC education film Iain shows they are absolutely in making the Earth a home for life. No force has played a more important role in creating the planet we know today.

His story begins in Ethiopia at the extraordinary volcano that is Erta Ale. Iain abseils down to the edge of one of only two lava lakes on Earth. It's a bubbling, seething cauldron of molten lava. This volcano offers a dramatic illustration of the heat that lies just beneath the Earth's surface - heat that fuels volcanoes, but also drives some of the most fundamental process on the planet.

In Iceland we discover how the Earth's inner heat drives the system of plate tectonics. At Thinvellir Iain dives between two continents - scuba diving in the eerily beautiful pools and canyons that have formed as Europe and America pull away from each other. At Rotorua in New Zealand Iain explores how volcanoes have played a critical role in keeping the planet habitable.

Early in the Earth's history the sun burned much less brightly than it does today. The planet was kept warming because the early Earth was highly volcanic, and all those eruptions poured out huge amounts of carbon dioxide. A natural form of global warming meant the planet stayed warm enough for early life to evolve. And it was most probably at volcanic hot springs similar to Rotorua that life first evolved.

We explain the critical role that the Earth's inner heat plays in shaping the Earth; without it Earth would be a waterworld, completely covered in a 4km deep ocean. New land is being continually created by the collision of the plates - a process which leads to violent earthquakes, and to the formation of great mountain ranges.

The Earth's inner heat fuels the movement of the plates, and it is this that counters the forces of erosion. Without the movement of the plates, the Earth wouldn't have a land surface at all. Iain discovers that volcanoes also played a critical role in saving the planet from one of the greatest disasters it has ever faced - Snowball Earth.

700 million years ago the planet completely froze over. A planet completely covered in ice reflects most of the sun's heat back into space, so once the Snowball took over the planet it seemed there was no escape. But over millions of years volcanoes kept erupting from under the ice, and gradually carbon dioxide built up in the atmosphere until a super greenhouse effect finally melted the snowball. Out of this great disaster life on Earth took a giant leap forward.

Until this time all life on Earth was simple, single celled bacteria. But within a few million years of the snowball ending, the first complex life had evolved. And in perhaps the most extraordinary twist of all, volcanoes and life have formed a partnership. Life removes carbon dioxide from the atmosphere, and when it dies and falls to the sea floor it becomes rock which eventually gets buried. After millions of years it is erupted in volcanoes' returning the carbon dioxide to the atmosphere.

This long, slow cycle, keeps the planet the right temperature for life. The Earth's inner heat shapes our world. It raises up great mountains, it levels cities, it creates new land, and destroys it too, it powers the evolution of life on Earth, and helps maintain the temperature of the planet. Without it the Earth would have become a dead planet millions of years ago.

Volcano is part of a series of geography teaching resources about the natural world from Earth - The Power of the Planet.

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