The Pacific Ocean is rimmed by a chain of active volcanoes, arranged in a series of graceful arcs and extending 30,000 kilometres from New Zealand through Fiji, New Guinea, the Philippines, Japan, the Aleutian Islands, and down the west coast of the Americas to Patagonia. This necklace of volcanoes, continually rocked by earthquakes, has been christened the 'Ring of Fire'. Scientists exploring the link between the Pacific Ocean and the earthquakes and volcanoes which surround it have formulated a remarkable theory, plate tectonics, which explains not only how the outer part of the Earth works, but how the continents themselves, and the mineral wealth they contain, were first formed and continue to grow.