Normal faults and extensional structures, the tectonic morphology of faults

Answer] Sleepy Servants: c

2021 Textbook P7

Knowledge points: geological structure is a fraud. The fault line is the intersection line between the fault and the ground, which indicates the extension direction of the fault, and its shape is determined by the shape of the fault plane and the bending and undulating conditions of the ground.

Faults are widely developed tectonic formations in tectonic movements. It's not the size.

First, the scale varies, from small ones of less than one meter to hundreds of meters and thousands of meters. But all of them disrupt the continuity and integrity of the rock formation.

In fault zones, rocks are often broken and easily eroded by weathering. Along the fault line, valleys often develop, and sometimes springs or lakes appear.

What are the forces that cause the rock formations to break and dislocate? It turns out that the strong pressure and tension generated by the movement of the earth's crust exceed the strength of the rock layer itself, which has a destructive effect on the rock. The surface where the rock strata are staggered is called the fault plane.

When the rocks in the middle of the two faults rise relatively, and when the rocks on both sides fall relatively, the rocks that rise relatively are called barriers; It often forms block-shaped mountains, such as Lushan and Mount Tai in China. When the rock blocks in the middle of the two faults fall relative to each other and the rock blocks on both sides rise relatively, a graben is formed, that is, a narrow and long depression zone. China's Fenhe Plain and Weihe Valley are both grabens.

Faults are particularly important for geoscientists because the sudden movement of crustal faults along the faults is the main reason for the occurrence of **. Scientists believe that the more they study the mechanisms of faults, the more accurately they will be able to predict and even control.

Normal fault: A type of geological structural fault layer. It is divided according to the relative displacement of the two disks of the fault.

After the fault is formed, the fault in which the upper wall is relatively lower and the lower wall is relatively rising is called a normal fault. It is mainly formed by the action of tensile tension and gravity. Normal faults are steep, usually above 45°, and more common at around 60°.

Normal faults are significant in the topography, mostly forming river valleys, gullies and lakes. Normal faults mostly occur at the boundary of the tension fracture plate.

A normal fault is a fault in which the upper wall moves downwards along the fault relative to the lower wall. It is generally believed that most normal faults are formed under the action of gravity and horizontal tension, so they are also called gravity faults. The inclination angle of the normal fault section is generally 45 degrees to 90 degrees.

A reverse fault is a fault in which the upper wall rises relatively along the fault plane. It is generally believed that reverse faults are formed by near and horizontal compressive stresses, so they are often associated with folds.