EARTH SCIENCE
EARTHQUAKES
Question
[CLICK ON ANY CHOICE TO KNOW THE RIGHT ANSWER]
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When the Earth’s plates move
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All of the above
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When stress on rock is great enough to cause a fracture
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When the Earth moves around the sun
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Detailed explanation-1: -A fracture will sometimes form a deep fissure or crevice in the rock. Fractures are commonly caused by stress exceeding the rock strength, causing the rock to lose cohesion along its weakest plane. Fractures can provide permeability for fluid movement, such as water or hydrocarbons.
Detailed explanation-2: -Faults occur when rocks break due to the forces acting on them. Stress may build up over a period of many years until the fault suddenly moves – perhaps a few centimetres, or even a few metres. When this happens, it releases a huge amount of energy in an earthquake.
Detailed explanation-3: -If rocks on one side of the break shift relative to rocks on the other side, then the fracture is a fault. If there is no movement of one side relative to the other, and if there are many other fractures with the same orientation, then the fractures are called joints.
Detailed explanation-4: -Compression stress squeezes rocks together. Compression causes rocks to fold or fracture (Figure below).
Detailed explanation-5: -Stress impacts the formation of small local faults, and broader tectonic plate boundaries. How the rock responds, depends on the type of stress and the conditions the rock is being subjected to when it encounters stress. It is this change in Earth’s crust that generates different types of faults and plate boundaries.