Investigating Plate Tectonics, Earthquakes, and Volcanoes

Investigating Plate Tectonics, Earthquakes, and Volcanoes — page 3
INVESTIGATING PLATE TECTONICs EARTHQUAKES AND VoICANOE At their edges the plates interact with each other in one of three ways they con verge diverge or slip past each other When two oceanic plates converge or come together the older denser plate slides under the younger plate When oceanic crust meets denser continental crust the oceanic crust slides underneath In other places plates diverge or spread apart In the middle of the oceans long ridges form where plates diverge Magma or molten rock rises from the man tle and fills in the gap creating new seafloor On the continents diverging plates create troughs called rift valleys The most extensive of these is East Africa s Great Rift Valley Along some boundaries two plates neither converge nor diverge instead they slide past each other along fractures in the crust These fractures are called transform faults The plates sometimes stick causing a buildup of pres sure that may be released in the form of an earthquake The sudden and sometimes vio lent shaking caused by earthquakes kills about IO 000 people a year Approximately 80 per cent of the world's earthquakes occur in the Ring of Fire a belt circling the Pacific Ocean that traces the boundaries of tectonic plates The Pacific Ring of Fire is also the site of about 90 percent of the world's