What is angular uncomformity?


Quick Answer

An angular unconformity is a geological phenomenon where an older layer of rock sits directly beneath a much younger layer of rock because the older layer was forced up at an angle, eroded, and younger rock deposited on top of it. An angular unconformity only stays constant for a relatively short distance into a rock face. Digging horizontally into the older rock reveals younger angled layers.

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Full Answer

Angular uncoformities are one of three major types of unconformities, where adjacent layers of rock are from very different time periods. The other two types are known as disconformities and noncomformities. A disconformity is like an angular unconformity, where a layer of much younger rock sits directly atop a layer of older rock, but rather than being caused by angling and erosion, the older rock layers are flat, and only erosion is involved. This occurs during repeated cycles of subsidence, deposition of rock layers, uplift and erosion, then subsidence and deposition again.

Unlike the other types of unconformity, which occur between layers of sedimentary rock, nonconformities occur between igneous or metamorphic rock and layers of sedimentary rock. Nonconformity is where younger sedimentary rock sits atop a much older igneous surface. Otherwise, the process that causes nonconformity is very similar to disconformities.

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