Читать книгу Incredible Hawaii - Terence Barrow - Страница 13

5 Drifting islands of Hawaii

THERE HAVE BEEN MANY THEORIES TO EXPLAIN THE origin of the Hawaiian chain of islands. Before modern geophysical studies of the floor of the world’s oceans, a theory prevailed that the surface of the earth was a more or less immovable crust. The Hawaiian Islands were believed by some to be formed by outwelling lava as a great rift or crack opened on the sea bottom. It now appears more likely that tectonic plates of earth’s crust drift around the globe at a rate of about seven feet per century.

According to the latter theory the vast Pacific plate on which Hawaii sits glides over the earth’s semi-fluid under-crust like a gigantic raft, and as this plate passes over a “hot spot” lava vent, islands are formed. The Big Island of Hawaii is now passing over this great vent and is thus still in formation. Some day Hawaii, like the other islands, will have moved on, and a new island will start to form. Islands appear to glide off in a northwest direction, riding on a giant plate which at its upper end moves under Japan and Asia, causing earthquakes from time to time.

The Hawaiian Islands have been in the process of creation and dissolution for about 20 million years. The earliest undersea volcanic mountains to break sea surface now stretch about 2,000 miles to the northwest of the Big Island, some worn down to rocky pinnacles or eroded to water-level reefs.