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Volcanoes are formed usually near plate boundaries, most commonly convergent/destructive plate boundaries, such as the Pacific Ring of Fire, which contains about 68% of Earth's volcanoes. A volcano is formed when there are cracks in the plates. When a denser plate, such as the oceanic plate, subducts under another plate, either a continental or oceanic plate, the subducted plate will melt under extreme temperatures in the mantle. This will form cracks in the plates, which results in magma flowing out from the mantle through the cracks in the plate and out onto Earth's surface. The magma will then harden and form layers, slowly forming a volcano. A shield volcano is formed when there is basic lava, which means it flows quickly over a large area before it cools and hardens; whereas an acid-lava or composite volcano is formed when there is acidic lava, which means it flows slowly over a small area before it hardens. Another reason for the formation of volcanoes is the hotspot theory. A hotspot is situated in the middle of a plate. It is situated beneath the plate, which means it does not move. It is magma source, and magma spews out of it onto Earth's surface to form volcanoes. However, the volcano is situated above the plate, so the volcano moves along with the plate. Since the hotspot does not move, the volcano becomes extinct as it is cut off from its magma source. A new volcano then forms on top of the hotspot and the cycle continues. Some examples are the Hawaii chain islands and Yellowstone. Earthquakes occur near plate boundaries and fault lines. It is when there are plate movements such as convergent, divergent or transform plate boundaries, with the strongest impact being the convergent plate boundary. When two plates slide or collide into each other, shockwaves are produced. These shockwaves will then affect things on Earth's surface, causing buildings to collapse and infrastructure to be destroyed. However, the strength of the shockwaves also depend on the ground (soil) that the buildings are built on. If it is strong, solid soil, it will be able to withstand and minimize the impact of the shockwaves. In a convergent plate boundary, two plates will approach each other. The denser plate will then subduct. Friction is produced and the ground shakes, depending on the strength of the quake, causing an earthquake. Shockwaves are radiated around the area, creating tremors. In a divergent plate boundary, two plates will move away from each other, causing the ground to sink, forming rift valleys. This will also cause earthquakes due to the sinking of land. In transform plate boundaries, where earthquakes usually happen, two plates move side by side in opposite directions. This will produce lots of friction when the two plates come into contact. The ground will vibrate and the tremors can be felt, however, not as strong as those in convergent, as they definitely will not exceed 8.5 on the Richter scale. If earthquakes occur in water bodies, a tsunami, which is a huge tidal wave, will occur. It will originate at the epicenter, which causes a rise or fall in the seafloor. A wave is then produced. However, it cannot be clearly seen, until it gets nearer to coast. The water travelling at fast speeds will start to form great waves when the seafloor gets shallower. It may be up to 7-10 stories high! It will then cause the coastal areas to be flooded. In some cases, earthquakes might be man-made. The 'earthquakes' are produced when buildings collapse, or there are bombings such as an atomic bomb or other strong-impact bombs. Gas pipes that explode underground can also cause shockwaves to be radiated out.

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16y ago

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