Characteristics of Igneous Rocks

The igneous rocks are also known as primary rocks as they form the basis of the formation of other types of bricks. Igneous rocks are formed because of the cooling, solidification, and crystallization of molten material known as magma. Igneous rocks mainly consist of alumino-silicate minerals such as quartz and feldspar. The Main Characteristics of Igneous Rocks are

Characteristics of Igneous Rocks

  • Hot lave pours out at the time of volcanic eruptions and cools down, later on, forming rocks.
  • The molten materials are known as magma, sometimes cool down beneath the earth’s crust, again forming rocks.
  • When the earth’s surface first became solid after it cooled down from its hot liquid state, the original rocks of the earth’s crust were formed. They are the Primary Igneous rocks, which are usually not found today.
  • Igneous rocks are generally harder and more granular.
  • There are no layers in Igneous rocks.
  • Fossils are not found in Igneous rocks.
  • The formation of Igneous rocks takes place beneath and above the surface of the earth.
  • Rocks formed by the cooling of molten matter beneath the earth’s surface are called intrusive igneous rocks. “Granite’ and ‘Gabbro’ are the main examples of these rocks.
  • The intrusive rocks are thus crystalline rocks.
  • Sometimes, the molten matter oozes out through cracks in the earth’s crust and spreads on the surface, forming extrusive igneous rocks.
  • Gabbro, Obsidian, Basalt, etc are examples of extrusive igneous rocks.
  • A very large area of the Deccan Plateau consists of basalt rocks.
  • These rocks contain silica from 40 to 80%, others are felspar, magnesium, and iron, etc
  • Other examples of Igneous rocks are-Granite, Pumic stone, Basalt, and Gabbro.

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5 Characteristics of Sedimentary Rocks

Sedimentary Rocks are formed by the deposition, sedimentation, and lithification of sediments over a long period of time. The Main Characteristics of Sedimentary Rocks are

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