In geology, there is a term called tectonism. If explained in detail, it has a close relationship with tectonic plate movements. The movement of tectonic plates will usually cause a shift in the layers of the Earth both vertically and horizontally. The movement is known as tectonism. The appearance produced by the shift of the plate usually results in fractures and folds resulting in changes in the shape of the Earth. The tectonic movements themselves are divided into 2 types, namely epeirogenic and orogenetic motion. Now to distinguish between the two movements, the differences will be explained below.
Epeirogenic motion is a movement that occurs in the layers of the Earth’s crust and usually, the movement is carried out horizontally and vertically (perpendicular). This movement is caused by the removal and decline of the Earth’s surface which lasts for a long time, moves slowly, and is also located in a very wide area. Epeirogenic itself is divided into 2 types of movements, namely positive epeirogenic and negative epeirogenic.
- Positive Epeirogenic
It is an epeirogenic movement where there is a downward movement of land, so that it looks as if by the surface of the water to rise. This event can be easily found on the river or on the beach. Examples are:
- There was a decline on several islands in Indonesia, such as in the Maluku Islands to the island of Banda. Each year the islands drop by 1 cm.
- The decline of the valley found in the Congo River, Africa to reach 2,000 km below sea level.
- Negative Epeirogenic
It is an epeirogenic movement where there is an increase in a land so it looks as if the surface of the water is going down. Examples of these events are:
- Rising highlands or plateaus in Colorado, United States experience lifting around 1,000 meters since 5 million years ago.
- An increase in the island of Simeulue in the north, during an Earthquake in Aceh, Indonesia.
- Stockholm Beach which has increased by about 1 meter every 100 years.
The characteristics of the epeirogenic movement can be seen from existing characteristics, such as the coastline. On the coastline, one of the signs of the epeirogenic movement can be easily seen whether there is a decrease or increase in sea level if so then epirogenetic plate movement has occurred.
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Orogenic comes from the word oros which means mountain and gennos which means forming so that the orogenic movement can be interpreted as a movement that forms mountains. The definition of orogenic is a movement that occurs on the surface of the Earth and the movement can be either a vertical movement or horizontal movement. The movement results in the movement of the Earth’s plate so that the surface of the Earth becomes elevated or dropped. This movement also takes place quickly and is in a narrow area. Orogenic movement can cause folds and also fractures.
This fold is the result of the orogenic movement carried out horizontally so that the shape of the Earth’s surface becomes wrinkled, folded, and eventually forms the surface of the Earth into mountains. In the fold that leads to the top is called the anticline while the part that folds downward is called the fold valley or syncline.
Types of folds include:
- An upright fold, the influence of horizontal power or radial energy is the same as tangential power.
- Sloping folds, a horizontal force that is not the same.
- Folds, there is a horizontal direction in one direction.
- Closed folds, there is tangential power.
- Fault hoods, there are movements that occur along with the Earth’s crust.
The fault is a horizontal or vertical movement so that the surface of the Earth becomes cracked or broken due to a strong enough pressure to pass through the broken point of the rock and occur very quickly.
Types of faults include:
- The land descends; the land is lower than the surrounding land due to a fault by the attraction of two directions so that the Earth’s crust drops.
- The land rises, the land is higher than the surrounding land due to a fault. This is caused by horizontal tectogenic movements (2-way or more movements so that the Earth’s crust rises).
- Fault, the fault caused by horizontal motion that is not frontal and only partially shifted. The fault itself is divided into 2 types, namely Sinistral and Dextral.
- Mountain Block, a collection of mountains composed of several faults. This fault occurs due to the presence of endogenous forces in the form of cracks.
Whereas the forms from the fault can be in the form of:
- The Mountains
It is a combination of several mountains that form the surface of the Earth which seems bumpy and there are valleys and grooves between mountains. There are 2 types of mountainous land, namely:
- Pacific Circum
- Mediterranean Circum: Inner arc and outer arc
It is a flat land that is at an altitude of 700 meters above sea level. These highlands can initially originate from the lowlands that experience rapture. Even so, the highlands have experienced erosion at this time. However, there are still remnants of erosion in the form of high peaks with the same height, such as in the highlands of Bandung, West Java and the Karo plateau, North Sumatra.
One form of the Earth in the form of a plateau, at the top, is relatively flat and has experienced erosion, for example, Dieng Plato in Central Java.
The shape of the Earth has decreased. The form of elongated depression is called Slenk while the rounded depression is called the Basin, for example, depression in Central Java.
- Sea Trench
The shape of this Earth is in the sea with a depth of more than 5,000 meters. The sea trough is elongated and narrow in shape. This is caused by a continuous sinking process, for example, the Sibolga Sea Trench.
- Sea Threshold
It is a barrier found on the sea floor that separates the two-deep seas. Examples include the Gilbatar Strait and the Sulu Sea Threshold.