The inclination of a flat or a planer part of a surface that is not horizontal c

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The inclination of a flat or a planer part of a surface that is not horizontal can be described by what is called its strike and dip. Strike is the compass bearing of a horizontal line on the inclined surface. Dip is the direction that a drop of water would flow down the surface and is measured as the angle down from the horizontal to this direction on the surface. Clearly, the directions of [] and [] are at right angles to each other. Differential stress exists when the acting stress on a body is not equal in the three, orthogonal, principle directions into which it can be resolved. Differential stress (tension, compression or shear) can result in brittle failure that produces fractures called joints and faults. Blocks of rock separated by joints show no appreciable offset movements. Joints arc confined to the upper part of rock bodies and do not extend to great depth. Blocks of rock separated by [] show noticeable to great displacements (vertical throws, horizontal offsets, or oblique movements) with respect to each other. Faults can extend throughout the depth that a rock can fracture. This first description of a fault for practical purposes occurred in a coal mine where a horizontal seam (bed) of coal being [] (excavated) was found to terminate abruptly against an inclined surface of barren rock. Having lost the continuation of the coal scam the miner was declared to be "at fault." The terminating surface, however, was found to feel rough when stroked down by hand and smooth (called []) when stroked up. This suggested that the surface was a fracture where the block of rock on the far side, which could contained the continuation of the coal, had been moved up. Having mined through the fracture, the floor the miner stood on was within the block of rock that had moved up. This was called the footwall block. The block that had been mined continued over the miner's head. This was called the headwall block. The fracture that allowed for upward movement of the footwall block relative to the headwall block became (reassigning the blame) called the fault. A raise (an upward sloping tunnel) was excavated in the footwall block and the continuation of the coal seam was found. This fault with movement of the footwall block up with respect to the headwall block was understood to be the action of horizontal tension that simultaneously moved the blocks away from each other. This type of fault was called a [] fault when a visa versa condition was found and called a [] fault. In the case of a reverse fault, the footwall block moves down with respect to the headwall block and is the action of horizontal compression that simultaneously moves the blocks toward each other. Horizontal shear results in faults with horizontally offset blocks. The fault is called a left-lateral transcurrent ([]) fault if the block on the far side of the fault has moved to the left and a [] transcurrent fault if it has moved to the right. Joints are usually sets of fractures: two at 45 degree to the principle direction of compressive or tensional stress and one normal to the principle direction of intermediate stress. Normal faults usually dip at an angle of 60-45 degree in the principle direction of tension and at depth can become listric (curved with lessening dip at depth). Reverse faults usually dip as an angle of 45--30 degree to the principle direction of compression and when their dip is less they are called [] faults. The dip of a transcurrent fault is usually vertical but can be at any angle. dip faults normal reverse right-lateral slickenside stoped strike-slip strike thrust

Explanation / Answer

Strike and dip faults stoped, normal reverse, thrust strike-slip Left lateral fault, right lateral fault strike-slip

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