- Definition of Rock
- Types of Rock
- Mode of Formation of Rock Types
- Characteristics of Rock Types
- Economic Importance of Rocks to Man
Definition of Rock
A rock is any solid substance that forms part of the earth crust. This solid substance may be hard, like granite or even be soft like mud. In other word, rocks are aggregates of minerals, that is, a combination of different minerals.
The most common rocks and their minerals include;
Types of Rock
There are three major types of rocks according to their origin, mode of formation and physical appearance. They are
1. Igneous Rocks
Mode of Formation
These rocks are formed from the cooling and solidification of molten rock or magma from the earth beneath. They are crystalline in nature. Examples are Basalt and Granite.
Types of Igneous Rocks
Igneous rock could be divided into two, namely: Intrusive or plutonic igneous rock and Extrusive or Volcanic Igneous rock.
(i) Intrusive Igneous Rocks
Intrusive Igneous rocks are rocks which solidified deep in the crust and they are only seen on the surface after a prolong erosive action.
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