Types Of Rocks-Characteristics,Country Of Location
TYPES OF ROCKS (INTRODUCTION)
Before i start talking about types of rocks,i will have to get down to what rock is all about.The earth’s crust consists of rocks.
A rock is any mineral material of the earth that can be in a combination of different mineral elements such as silica which contains silicon and oxygen.
TYPES OF ROCKS
Rocks are being classified into three major types;they are;
- Igneous Rocks
- Sedimentary Rocks
- Metamorphic Rocks
Igneous rocks are those rocks formed by the cooling and solidification of molten rocks called magma which is being ejected from beneath the earth’s crust.The magma which results from high temperature and pressure beneath the earth,forces itself towards the earth’s surface through cracks. As the magma moves towards the surface,it comes in contact with lower temperature,then solidifies to form igneous rocks.
Characteristics of igneous rocks
- They are resistant to erosion and other elements of climate
- They do not contain fossils
- They are usually hard and impervious
- They do not occur in layers meaning that they are non-stratified rocks.
Types of igneous rocks
There are two types of igneous rocks:
A) Plutonic (intrusive) igneous rocks: These are rocks formed when molten magma cools and solidifies slowly before it gets to the surface of the earth to form large crystals. As a result of prolonged erosion,the plutonic igneous rocks will later be exposed to the surface of the earth. Examples of plutonic igneous rocks are: granite,gabbro and diorite.
B) Volcanic (extrusive) igneous rocks: These rocks are formed when the molten magma cools and solidifies rapidly on getting to the surface of the earth to form small crystals. An example of volcanic igneous rock is basalt
Three countries you can find igneous rocks
There are some other countries which you can find igneous rocks apart from the ones mentioned below:
Sedimentary rocks are those rocks that are formed from sediments deposited either by water,by wind or by ice. These sediments are deposited in layers or strata;that is one layer on top the other and after a long period of time,they become hardened by compression to form sedimentary rocks. The plane between two strata of sedimentary rock is called Bedding Plane
Characteristics of sedimentary rocks
- They do not exist in crystals
- They occur in layers or strata
- The rocks may be coarse,fine soft or hard
- They contain fossils of plants and animals
- They are not resistant to erosion
Types of sedimentary rocks
Based on the process of formation,there are three types of sedimentary rocks.
- Mechanically formed sedimentary rocks: These rocks are formed from sediments of other rocks that have accumulated and cemented together over a long period of time. Examples are shale,clay,sandstones,breccia,conglomerate.
- Organically formed sedimentary rocks: These are rocks formed from the remains of living organisms.When sedimentary rocks are formed from the remains of animals like corals or shellfish,such rocks are called calcareous rocks, examples limestone and chalk. But when sedimentary rocks are formed from the remains of vegetable matter such as swamps and forest,they are called carbonaceous rock. Examples are coal,peat,lignite,petroleum etc.
- Chemically formed sedimentary rocks: These rocks are precipitated chemically from rock solution.Examples are potash,sodium chloride(common salt),nitrate,gypsum and dolomite.
Importance of sedimentary rocks to man
- They are source of minerals e.g coal,gold,petroleum.
- Sedimentary rocks are source of materials for construction.
- They determine the quality of soil nutrient
- They determine the availability of and supply of underground water.
- They are used as medicines.Example kaolin
- They are source of raw materials for cement.
Countries you can find sedimentary rocks
Like i said earlier there are so many countries you can find them but am going to mention but a few
- USA(southwestern utah)
Metamorphic rocks are changed rocks which are formed from pre-existing igneous or sedimentary rocks which have been changed as a result of great heat and pressure. The original character and appearance may be greatly altered or changed by such forces. Examples of metamorphic rocks are: slate,marble,schist,graphite,quartzite,gneiss.
Slate is formed from clay,marble is formed from limestone,quartzite is formed from sandstone,gneiss is formed from granite,schist is formed from shale,graphite is formed from coal.
countries to find metamorphic rocks