Task: Question Generation
Input (English): A rock under enough stress will fracture. There may or may not be movement along the fracture. If there is no movement on either side of a fracture, the fracture is called a joint. The rocks below show horizontal and vertical jointing. These joints formed when the confining stress was removed from the rocks as shown in (Figure If the blocks of rock on one or both sides of a fracture move, the fracture is called a fault (Figure 1.2). Stresses along faults cause rocks to break and move suddenly. The energy released is an earthquake. How do you know theres a fault in this rock? Try to line up the same type of rock on either side of the lines that cut across them. One side moved relative to the other side, so you know the lines are a fault. Slip is the distance rocks move along a fault. Slip can be up or down the fault plane. Slip is relative, because there is usually no way to know whether both sides moved or only one. Faults lie at an angle to the horizontal surface of the Earth. That angle is called the faults dip. The dip defines which of two basic types a fault is. If the faults dip is inclined relative to the horizontal, the fault is a dip-slip fault (Figure 1.3). There are two types of dip-slip faults. In a normal fault, the hanging wall drops down relative to the footwall. In a reverse fault, the footwall drops down relative to the hanging wall. This diagram illustrates the two types of dip-slip faults: normal faults and reverse faults. Imagine miners extracting a re- source along a fault. The hanging wall is where miners would have hung their lanterns. The footwall is where they would have walked. A thrust fault is a type of reverse fault in which the fault plane angle is nearly horizontal. Rocks can slip many miles along thrust faults (Figure 1.4). At Chief Mountain in Montana, the upper rocks at the Lewis Overthrust are more than 1 billion years older than the lower rocks. How could this happen? Normal faults can be huge. They are responsible for uplifting mountain ranges in regions experiencing tensional stress. A strike-slip fault is a dip-slip fault in which the dip of the fault plane is vertical. Strike-slip faults result from shear stresses. Imagine placing one foot on either side of a strike-slip fault. One block moves toward you. If that block moves toward your right foot, the fault is a right-lateral strike-slip fault; if that block moves toward your left foot, the fault is a left-lateral strike-slip fault (Figure 1.5). Californias San Andreas Fault is the worlds most famous strike-slip fault. It is a right-lateral strike slip fault (See opening image). People sometimes say that California will fall into the ocean someday, which is not true. Strike-slip faults. Click image to the left or use the URL below. URL:
Output (English): strike slip faults result from __________ stresses.