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火山沉陷是指由若干火山口(或火口构造)及其组合所构成的大型洼地,其四壁陡峻,内部平缓而近于圆形,直径一般在三十公里以上。它通常经历了喷发和喷发后的沉陷(下陷)两个演化阶段。前者以猛烈喷发形成山火碎屑岩及熔岩堆积为特征;后者是在强烈喷发之后,由于火山产物与下伏岩浆房之间压力失去平衡,使火山洼地的中间地块沿环状断裂发生下陷,形成以沉积岩、火山沉积岩为主的湖相或河湖相沉积为标志。继下陷之后,当下伏岩浆房重新获得岩浆补给并在其压力作用下,原来下陷的地块又以构造隆起
Volcano depression refers to a number of crater (or crater structure) and its combination of large depression, the steep walls, the interior is smooth and nearly circular, the diameter is generally more than thirty kilometers. It usually experiences two stages of evolution following the eruption and subsidence (sag). The former is characterized by intense eruptions of pyroclastic rocks and lavas; the latter, after intense eruptions, occur along annular fractures due to a loss of pressure balance between volcanic products and underlying magma chambers Subsidence, the formation of sedimentary rocks, volcanic sedimentary rock-based lacustrine or lacustrine deposits as a symbol. Subsequent to the subsidence, when the underlying magma chamber regains magmatic replenishment and under its pressure, the originally subsided massif is again structurally uplifted