Jellyfish, Polyps and Worms?

• Main Author: Southwood, T R E
• Format: Book Part
• Language: unknown
• Published: Oxford University PressOxford 2003
• Subjects: Kamchatka; Kamchatka Peninsula
• Online Access: http://dx.doi.org/10.1093/oso/9780198525905.003.0004; https://academic.oup.com/book/chapter-pdf/52320358/isbn-9780198525905-book-part-4.pdf

Abstract The continents of the earth move. The crust (lithosphere) consists today of seven large tectonic plates and a number of smaller ones. Several of them have continents attached to their ‘backs’, and shuffle across the globe, moved by the deeper convection currents of the liquid rock in the middle layer, the mantle. When the plates move away from each other in the deep ocean, liquid rock (magma) flows upwards and solidifies to form ridges. In some other places the plates may scrape past each other, causing fault lines (such as the San Andreas Fault). When they collide directly, one passes below the other, a process known as subduction. If this happens where the plates are ‘carrying’ continents then these buckle and rise to form mountains (for example, the Himalayas). Most volcanic activity occurs around the edges of the plates, but some submarine mountains and volcanic islands arise towards the middle of plates. These are due to hot spots, which are generated in particular stationary sites in the mantle. As the plates move across a hot spot a chain of volcanoes are successively ‘punched ‘ through it; only one end of the chain is active — where the plate is currently over the hot spot. The Hawaiian Islands and the older line of submarine mountains, known as the Emperor Seamounts (see map p. 176), that stretch up to the Kamchatka Peninsula, are a spectacular example of the effects of a hot spot and show how the Pacific plate has moved over the past 75 million years.