Topics in GeographyThe Solar System Layers and Composition of the Atmosphere Types and Branches of Geography Types of Rocks
Academic Questions in Geography
We have 3 main types or classes of rock namely, igneous rock, sedimentary rock and metamorphic rock. These classification of rock is based on how they are formed.
Igneous rocks are formed when molten substances below the earth surface cools down and solidifies. These molten substances are called magma or lava. Magma can be derived from melting of existing rocks on the earth crust. The solidification of molten magma into igneous rock may be below the earth surface (intrusive) or on the earth surface (extrusive), giving rise to the two types of igneous rock.
Intrusive Igneous Rock: These are igneous rocks that crystallizes below the earth’s surface. They generally cool slowly during the process of solidification and tend to produce large crystals. They are also referred to as plutonic igneous rock. Examples are gabbro, granite and pegmatite.
Extrusive Igneous Rock: They are igneous rocks that form when molten magma erupts on top of the earth's surface. They cool down and solidify quickly, producing small crystals in the process. Sometimes, the molten magma cools so quickly, allowing no time for crystals to grow. This rapid cooling results in the formation of an amorphous glass. They are also referred to as volcanic igneouse rock. Examples are basalt, rhyolite and scoria.
Sedimentary rocks amount to about 76% of the earyth's surface. They can be formed in different ways;
Clastic sedimentary rock require 4 basic proesseses during their formation:
Examples of Sedimentary rocks include chalk, limestone, sandstone and clay.
Weathering refers to the many processes of physical and chemical breakdown of rocks when exposed to the air and water.
Lithification is a process of rock formation whereby pressure squeezes the rock sediments into layered solids while the connate fluids are expelled.
Diagenesis is a term used to describe all the chemical, physical, and biological changes a sediment undergoes after its initial deposition and during and after its lithification. it is not dependent on surface weathering.
Metamorphic rocks results from the transformation of an existing rock or original rock called protolith. This protolith may be an igneous rock or a sedimentary rock or another older metamorphic rock. Their transformation may be physical or chemcal, requiring great heat and pressure. Metamorphic rocks are always more dense and also less likely to be broken down by erosion when compared to igneous and sedimentary rocks. They make up about 12% of the earth crust and can also be formed beneath the earth surface.
Examples of metamorphic rocks are schist (a converted basalt), quartzite (a compressed sandstone), and marble (a compressed limestone or dolomite).
Amazing facts in Geography
Instabul is a city in Turkey. It's the only city that lies between two continents. Instabul lies between Europe and Asia
It is believed that the Amazon rainforest is responsible for producing about 20% of earth's oxygen.
Please read on tropical rainforest here.
The middle part of the earth or (center of the earth) is actually hotter than the sun
There are actually three countries in the world that are present inside another country. These are:
NOTABLE POINTS IN Geography