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A flood basalt is the result of a giant volcanic eruption or series of eruptions that coats large stretches of land or the ocean floor with basalt lava. Flood basalt provinces are often called traps, which derives from the characteristic stairstep geomorphology of many associated landscapes. Eleven distinct flood basalt episodes occurred in the past 250 million years, resulting in large volcanic provinces, creating plateaus and mountain ranges on Earth. Large igneous provinces have been connected to five mass extinction events, and may be associated with bolide impacts. == Formation == The formation and effects of a flood basalt depend on a range of factors, such as continental configuration, latitude, volume, rate, duration of eruption, style and setting (continental vs. oceanic), the preexisting climate state, and the biota resilience to change. One proposed explanation for flood basalts is that they are caused by the combination of continental rifting and its associated decompression melting, in conjunction with a mantle plume also undergoing decompression melting, producing vast quantities of a tholeiitic basaltic magma. These have a very low viscosity, which is why they 'flood' rather than form taller volcanoes. Another explanation is that they result from the release, over a short time period, of melt that has accumulated in the mantle over a long time period. The Deccan Traps of central India, the Siberian Traps, and the Columbia River Plateau of western North America are three regions covered by prehistoric flood basalts. The largest and best-preserved continental flood basalt terrain on Earth is part of the Mackenzie Large Igneous Province in Canada.〔(Muskox Property - The Muskox Intrusion )〕 The maria on the Moon are additional, even more extensive, flood basalts. Flood basalts on the ocean floor produce oceanic plateaus. The surface covered by one eruption can vary from around 200,000 km² (Karoo) to 1,500,000 km² (Siberian Traps). The thickness can vary from 2000 metres (Deccan Traps) to 12,000 m (Lake Superior). These are smaller than the original volumes due to erosion. 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「Flood basalt」の詳細全文を読む スポンサード リンク
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