There is almost no volcanic activity around continental-continental convergent boundaries. We know that Mount Everest is the Earth’s tallest mountain (above water, that is), and as part of the Himalayas, a convergent plate boundary between the Indian and Eurasian Plates has built it.īecause there is no subduction at this type of boundary, however, the continental lithosphere does not melt easily. Subduction is not the only tectonic process responsible for the world’s geologic hazards! When two continental plates collide at a convergent boundary, the lithosphere is too buoyant to subduct, and large mountain chains build upward toward the sky. Mount Everest and the Himalayas have formed by mountain-building at a convergent boundary between the Indian and the Eurasian Plates. The process of subduction at convergent boundaries will produce volcanoes and moderate to severe earthquakes! Gigantic Mountain Ranges Figure 2.8.3. Some of these earthquakes originate under seawater, which can result in giant tsunamis, such as the 2004 Indian Ocean Earthquake and the 2011 Tōhoku Earthquake in Japan. Once the rock does rupture under the stress, it releases the energy it built up over those many years in the form of a seismic wave – an earthquake occurs.īecause this energy is released from a plate that underwent tremendous stress deep beneath the Earth’s surface, the earthquakes at subduction zones can be as devastating as 9.0 in magnitude. There is a limit to the amount of stress a rigid object, such as a rock, can tolerate before it breaks. When cold, the rigid lithosphere sinks into the asthenosphere, stress from that movement will build up in the rocks over long periods of time. Volcanoes are not the only consequence of subduction zones. At a subduction zone associated with a convergent boundary, melting of the lithosphere by released water will cause volcanism, and the movement of the slab will cause earthquakes and possibly tsunamis. The release of volatiles, such as water, from the subducting slab enables the overriding lithosphere to melt easier, and volcanic arcs form. The Ring of Fire is infamous for having heightened volcanic and earthquake activity, and that is a direct consequence of tectonic activity.Ĭonvergent plate boundaries involving subduction primarily occur throughout the Ring of Fire. If you have ever had a unit on earthquakes and volcanoes in school or watched a documentary on the subject, chances are good that you may have heard of a region called the “Ring of Fire.” Not to be confused with the Johnny Cash song, the Ring of Fire is enormous! It extends for around 40,000 km around the coasts that border the Pacific Ocean – from New Zealand to the Philippines, Japan, Alaska, the western coast of the United States, Mexico, and all the Western Coast of South America. Map displaying the Pacific Ring of Fire (shaded red regions). However, what does all of this have to do with the geologic hazards and disasters that impact our society daily? In this section, we will explore how we can predict, and even come to expect, certain types of disasters near plate boundaries. This theory also explains why we have tall mountain ranges, valleys, and deep ocean trenches. Plate tectonics explains why our oceans open and continents move throughout Earth’s history. 2.8 Predicting Geologic Hazards at Tectonic Boundaries
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