Earth Science. May 15, Convergent plates come together, while divergent plates pull apart. Explanation: Convergent plates converge, or come together. Earthquakes are caused by movement among the tectonic plates.
Related questions How do I determine the molecular shape of a molecule? What is the lewis structure for co2? When two plates come together, it is known as a convergent boundary. Convergent boundaries occur between oceanic - oceanic lithosphere, oceanic - continental lithosphere, and continental - continental lithosphere. The geologic features related to convergent boundaries vary depending on crust types.
Plate tectonics is driven by convection cells in the mantle. The Cascade Mountain Range is a line of volcanoes above the melting oceanic plate. The Andes Mountain Range of western South America is another example of a convergent boundary between an oceanic and continental plate. Here the Nazca Plate is subducting beneath the South American plate. Magnitude 9 earthquakes only occur on subduction zones.
As stated above, there hasn't been an active subduction zone under San Francisco or Los Angeles for millions of years. However, earthquake intensity along the modern-day San Andreas fault maxes out at approximately 8.
The location where two plates meet is called a plate boundary. Basically, because it's a big fault that is close to some big cities. While it is not as likely to experience a 7. That was when San Francisco experienced an estimated magnitude The lines that bring water, electricity and gas to Los Angeles all cross the San Andreas fault —they break during the quake and won't be fixed for months.
Are They Dangerous Places to Live? Mountains, earthquakes, and volcanoes form where plates collide. If we choose to live near convergent plate boundaries , we can build buildings that can resist earthquakes, and we can evacuate areas around volcanoes when they threaten to erupt.
If two tectonic plates collide, they form a convergent plate boundary. The new magma molten rock rises and may erupt violently to form volcanoes , often building arcs of islands along the convergent boundary. What happens when two continental plates collide?
Instead, a collision between two continental plates crunches and folds the rock at the boundary, lifting it up and leading to the formation of mountains and mountain ranges.
Picture two giant conveyor belts, facing each other but slowly moving in opposite directions as they transport newly formed oceanic crust away from the ridge crest. Perhaps the best known of the divergent boundaries is the Mid-Atlantic Ridge. This submerged mountain range, which extends from the Arctic Ocean to beyond the southern tip of Africa, is but one segment of the global mid-ocean ridge system that encircles the Earth. The rate of spreading along the Mid-Atlantic Ridge averages about 2.
This rate may seem slow by human standards, but because this process has been going on for millions of years, it has resulted in plate movement of thousands of kilometers. Seafloor spreading over the past to million years has caused the Atlantic Ocean to grow from a tiny inlet of water between the continents of Europe, Africa, and the Americas into the vast ocean that exists today. The volcanic country of Iceland, which straddles the Mid-Atlantic Ridge, offers scientists a natural laboratory for studying on land the processes also occurring along the submerged parts of a spreading ridge.
Iceland is splitting along the spreading center between the North American and Eurasian Plates, as North America moves westward relative to Eurasia. The map also shows Reykjavik, the capital of Iceland, the Thingvellir area, and the locations of some of Iceland's active volcanoes red triangles , including Krafla. The consequences of plate movement are easy to see around Krafla Volcano, in the northeastern part of Iceland. Here, existing ground cracks have widened and new ones appear every few months.
From to , numerous episodes of rifting surface cracking took place along the Krafla fissure zone. Some of these rifting events were accompanied by volcanic activity; the ground would gradually rise m before abruptly dropping, signalling an impending eruption. Between and , the displacements caused by rifting totalled about 7 m.
When the continental crust stretches beyond its limits, tension cracks begin to appear on the Earth's surface. Magma rises and squeezes through the widening cracks, sometimes to erupt and form volcanoes. The rising magma, whether or not it erupts, puts more pressure on the crust to produce additional fractures and, ultimately, the rift zone. East Africa may be the site of the Earth's next major ocean.
Plate interactions in the region provide scientists an opportunity to study first hand how the Atlantic may have begun to form about million years ago. Geologists believe that, if spreading continues, the three plates that meet at the edge of the present-day African continent will separate completely, allowing the Indian Ocean to flood the area and making the easternmost corner of Africa the Horn of Africa a large island.
The size of the Earth has not changed significantly during the past million years, and very likely not since shortly after its formation 4. The Earth's unchanging size implies that the crust must be destroyed at about the same rate as it is being created, as Harry Hess surmised. Such destruction recycling of crust takes place along convergent boundaries where plates are moving toward each other, and sometimes one plate sinks is subducted under another. The location where sinking of a plate occurs is called a subduction zone.
The type of convergence -- called by some a very slow "collision" -- that takes place between plates depends on the kind of lithosphere involved. Convergence can occur between an oceanic and a largely continental plate, or between two largely oceanic plates, or between two largely continental plates.
If by magic we could pull a plug and drain the Pacific Ocean, we would see a most amazing sight -- a number of long narrow, curving trenches thousands of kilometers long and 8 to 10 km deep cutting into the ocean floor.
Trenches are the deepest parts of the ocean floor and are created by subduction. Off the coast of South America along the Peru-Chile trench, the oceanic Nazca Plate is pushing into and being subducted under the continental part of the South American Plate. In turn, the overriding South American Plate is being lifted up, creating the towering Andes mountains, the backbone of the continent.
Strong, destructive earthquakes and the rapid uplift of mountain ranges are common in this region. Even though the Nazca Plate as a whole is sinking smoothly and continuously into the trench, the deepest part of the subducting plate breaks into smaller pieces that become locked in place for long periods of time before suddenly moving to generate large earthquakes.
Such earthquakes are often accompanied by uplift of the land by as much as a few meters.
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