Tectonics and Orogenic Movements

Tectonism is the third biggest earth forming movement that takes place when the crust of the earth becomes deformed due to great amounts of pressure. This type of movement normally takes place over a long period of time and cannot be perceived by people.

Even in cases when the movements are quicker, such as like what occurred in the sinking of Long Beach, California because of the removing of enormous pools of oil underneath the city, the movement that occurs might not be noticed for a number of years.

It is known though that tectonic movements can occur very quickly and can actually take place in a matter of seconds and when this does happen, the end result is what we know as earthquakes.

The most known of types of tectonism are epeirogeny and orogeny. Epeirogenic movements consist of the slow modifications that can take up to centuries and eons for them to make a change that can be perceived in the crust of the earth.

Orogenic movements are what are known as mountain making movements. These are in general a bit more rapid than epeogenic changes however, they are still slow and can take up to thousands of years.

The deformation of rocks that occurs from orogenic and epeirogenic movements is very vital to prospectors. The following terms are words that can be found in geological reports in mining.

Warping takes place when big areas of rocks get lifted or lowered under the crust of the earth. When the strata is looked at superficially, it would look like a straight line parallel to the surface. If this examination were done scientifically it would be seen that the strata actually inclined a little towards the center of the earth.

When rock strata has been under a great amount of pressure from one or two directions it is considered to fold. Folds can go in one direction however it is more common to see the strata is curved up or downwards. When pressure is placed on it, it causes it to bend. 

When it comes to fold, an anticline is occurs when the strata is folded upwards with the outside of the curve lines pointing down. A syncline happens when the strata gets folded downwards while the curved part is pointed upwards.

When folds have been diagrammed, geologists have used the same expressions that are used when a mineral lode is described. This is known as the attitude of the strata. The directional plane of the strata is the compass heading that is taken on a flat area where the strata intersects with it. The dip is the slant of leaning that is created between the strata and the flat line utilized for the strike.

Another thing that is important when it comes to geology are fractures and this is often times how the lodes are seen and in occasions lost in the process of mining. A fracture is simply an area where rock strata has become fractured.

There are different types of fractures though and the simple ones are known as joints and they usually occur because of contraction when the original rock strata cooled. It is exemplified by just a little bit or no movement at all of the strata when in relation to the part it has broken or fractured from.

When a great deal of pressure causes a great amount of movement along the area of the earth’s crust is it known as a fault. There has been a lot of mention of this word however it is not always well understood by the average person. Before explaining the kinds of faults there are, it is first needed to list the words that are utilized to explain the different parts of a fault.

The rocks or strata are moved along the fault plane or the areas where the fracture occurs. The amount of movement that takes place along the fault plane is known as the displacement. As we had said before in folds, strike and dip have the same meaning when they are applied to faults. The plane that bounds the lower part of an inclined fault is called footwall and the one above is known as hanging wall.