#Interior of the Earth, #Direct Sources, #Indirect Sources, Interior of the Earth
The interior of the earth can be understood only by indirect evidences as neither anyone has nor anyone can reach the interior of the earth. The radius of earth is 6370 km.
There are two direct sources one is to reach the crust and second is by volcanic eruption.
For example – gold mines in South Africa are as deep as 3-4 km. Going beyond this depth is not possible as it is very hot at this depth.
Scientists have taken up number of projects to penetrate deeper depth. Such as
The deepest drill at Kola in Arctic Ocean has so far reached a depth of 12 km.
During the process of Volcanic eruption when magma is thrown out of the surface of the earth, it becomes available for laboratory analysis.
We know through the mining activity that the temperature and pressure increase with increasing distance from the surface towards the interior in deeper depths.
All natural earthquakes take place in the lithosphere. Lithosphere refers to the portion of depth up to 200 km from the surface of the earth. An instrument called ‘Seismograph‘ records the waves reaching the surface.
Earthquake waves get recorded in Seismographs located at far off locations. However, there exist some specific areas where the waves are not reported. Such a zone is called a shadow zone.
Continental Crust vs Oceanic Crust
A volcano is a place where gases, ashes and/or molten rock material – lava – escape to the ground.
The mantle contains a weaker zone called asthenosphere. It is from this that the molten rock materials find their way to the surface.
The material in the upper mantle portion is called magma. Once it starts moving towards the crust or it reaches the surface, it is referred to as lava.
On the basis of nature of eruption and the form developed at the surface. Major types of volcanoes are as follows:
Barring the basalt flows, the shield volcanoes are the largest of all the volcanoes on the earth. The Hawaiian volcanoes are the most famous examples. These volcanoes are mostly made up of basalt, a type of lava that is very fluid when erupted.
These volcanoes are characterised by eruptions of cooler and more viscous lavas than basalt. These volcanoes often result in explosive eruptions. Along with lava, large quantities of pyroclastic material and ashes find their way to the ground.
The lava that is released during volcanic eruptions on cooling develops into igneous rocks.
The cooling may take place either on reaching the surface or also while the lava is still in the crustal portion. The lava that cools within the crustal portions assumes different forms.
Depending on the location of the cooling of the lava, igneous rocks are classified as
|Structure of the Earth|