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The upper part of the asthenosphere is believed to be the zone upon which the great rigid and brittle lithospheric plates of the Earth's crust move about. Due to the temperature and pressure conditions in the asthenosphere, rock behaves plastically, moving at rates of deformation measured in cm/yr over lineal distances of thousands of kilometers. In this way, it flows like a convection current, radiating heat outward from the Earth's interior. Above the asthenosphere, at the same rate of deformation, rock behaves elastically and, being brittle, can break, causing faults. The rigid lithosphere is thought to "float" or move about on the slowly flowing asthenosphere, creating the movement of crustal plates described by Plate Tectonics theory.

Although its presence was suspected as early as 1926, the worldwide occurrence of the asthenosphere was confirmed by analyses of earthquakeAn earthquake is a trembling or shaking movement of the Earth's surface. Earthquakes typically result from the movement of faults, quasi-planar zones of deformation within its uppermost layers. The word earthquake is also widely used to indicate the sourc waves from the ChileThe word chile may also refer to Chilli pepper. The Republic of Chile is a republic located on the southwestern coast of South America. It is a long and narrow piece of land between the Andes mountains and the Pacific Ocean. It shares borders with Argentian Great earthquakeThe Great Chilean Earthquake of May 22, 1960, was an earthquake measuring 9. 5 on the Richter scale (9. It affected southern Chile. Its epicenter was located in Valdivia, Chile, approximately 700 kilometers (435 miles) south of Santiago. The earthquake ca of May 22May 22 is the 142nd day of the year in the Gregorian calendar (143rd in leap years). There are 223 days remaining. Events 1176 Murder attempt by the Hashshashin (Assassins) on Saladin near Aleppo. 1455 Wars of the Roses: First Battle of St Albans Richard,, 1960Events January-February January 1 Independence of Cameroon January 9 Aswan High Dam construction begins in Egypt January 11 Chad declares its independence. January 14 Ralph Chubb, the gay poet and printer, dies at Fair Oak Cottage in Hampshire. January 23.