Topics in GeographySolar System: Classification, Types and Characteristics of Planets Atmosphere: Layers, Functions and Composition of the Atmosphere Geography, Types and Branches of Geography Types, Characteristics and Examples of Rocks: Igneous, Sedimentary and Metamorphic Rocks
Academic Questions in Geography
We have 3 main types or classes of rock based on how they are formed. These are; igneous rock, sedimentary rock and metamorphic rock.
Image Credit: Pinterest
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's surface (intrusive) or on the earth's 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.
Intrusive Igneous Rock 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.
Extrusive Igneous Rock are also referred to as Volcanic Igneous Rock. Examples are basalt, rhyolite and scoria.
Image Credit: Cailin's Rock
Sedimentary rocks amount to about 76% of the earth's surface. They can be formed in different ways;
Clastic sedimentary rock require 4 basic processes during their formation. These are:
Examples of Sedimentary rocks include chalk, limestone, sandstone and clay.
Note the followings
Weathering refers to the processes that involves the 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 lithification.
Diagenesis is not dependent on surface weathering.
Image Credit: Miracosta
Metamorphic rocks are formed from the transformation of an existing rock or original rock called protolith. The protolith may be an igneous rock or a sedimentary rock or another older metamorphic rock. Their transformation may be physical or chemical, 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).
THANKS FOR READING - Please Help Share!
Alfred Ajibola is a Medical Biochemist, a passionate Academician with over 7 years of experience, a Versatile Writer, a Web Developer, a Cisco Certified Network Associate and a Cisco CyberOps Associate.
Amazing facts in Geography
Earth is the only planet that contains water on it's surface. In fact, the percentage of water on Earth is greater than that of land.
Salt water or Saline water makes up about 97% of Earth's water. It comprises majorly of ocean and sea waters
Metal actually rains on planet Venus
Planet Mars appear brownish/red because it's covered with iron rust.
China is the largest emitter of carbon IV oxide (CO2) in our world today
There are over 125 billion galaxies in our universe. Our galaxy (called the milky way) has about 100-400 billion stars.
The 🌞 sun is actually a 🌟 star; and a single star can be 100 times bigger than the earth.
It is estimated that 50% of all gold ever mined on Earth came from South Africa.
Infact, it came from a single plateau in South Africa called Witwatersrand
We have 7 continents. All the 7 continents ends with the alphabet that began it.
The continents are:
- North America
- South America
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.
NOTABLE POINTS IN Geography