Grade Level: JrH-Adult
Producer: BBC
Closed Captioned: No |
Running Time: 50 mins
Country of Origin: Great Britain
Study Guide: No |
Copyright Date: 1998
Available in French: No
|
This film is about plate tectonics – earthquakes, volcanoes and the formation of the continents. The great Alaskan earthquake of 1964 (the most powerful ever recorded) provided the first clue in a scientific detective story that led to a new understanding of the planet's surface. In the aftermath of the ‘quake, American geologist George Plafker noticed something odd – a line of dying barnacles several feet above the high-water line. Visiting the site, George tells how this observation led to the theory of plate tectonics. Scientists now realise that the entire surface of the world is in constant motion, and that all around the Pacific, the ocean floor is sliding back into the planet's interior beneath the neighbouring continents – a fact which explains the earthquakes that plague the nations of the Pacific Rim, from South America to Japan and New Zealand. But how do the volcanoes also found all round the Pacific fit into this theory? In search of an answer, Earth Story climbs 6,000m up one of the world's highest active volcanoes in the Bolivian Andes. The water collected from the summit turns out to be Pacific sea-water, which has completed an extraordinary 100,000,000 year journey through the Earth. It is this seawater, dragged down into the Earth's interior by the sinking ocean floor, which is the ultimate cause of the volcanoes. It acts like anti-freeze on the hot rocks of the Earth's mantle, causing them to melt and erupt in the arc of volcanoes known as the Ring of Fire. As this molten magma rises through the crust, it adds material to the Earth's continents. Evidence in Britain's Lake District reveals this is how all continents form – as the sea floor is destroyed, so the dry land is born. |
