{"id":451,"date":"2020-09-07T16:18:46","date_gmt":"2020-09-07T16:18:46","guid":{"rendered":"https:\/\/sharedlearning.in\/dailyprep\/?p=451"},"modified":"2020-09-07T16:19:48","modified_gmt":"2020-09-07T16:19:48","slug":"the-structure-of-earth","status":"publish","type":"post","link":"https:\/\/old.sharedlearning.in\/dailyprep\/2020\/09\/07\/the-structure-of-earth\/","title":{"rendered":"THE STRUCTURE OF EARTH"},"content":{"rendered":"

\"\"<\/p>\n

The internal structure of earth is layered in spherical shell: an outer silicate solid crust, a highly viscous asthenosphere<\/strong> and mantle, a liquid outer core that is much less viscous than the mantle, and solid inner core. The scientific understanding of the internal structure of earth is based on observations of topography<\/strong> and bathymetry<\/strong>, observations of rock, analysis of the seismic waves, measurement of the gravitational and magnetic fields of earth.<\/p>\n

\"\"<\/p>\n

Earth can be divided into crust, upper mantle, lower mantle, outer core, and inner core.<\/p>\n

\n

CRUST<\/strong><\/h4>\n<\/blockquote>\n

It is the outermost and the thinnest layer of the earth’s surface. The Earth’s crust ranges from 5 – 70 km in depth. The thin parts are the oceanic crust, which underline the ocean basins(5 – 10 km) and are composed of dense iron magnesium silicate igneous rocks, like basalt. The thick crust is continental crust, which is less dense and composed of potassium aluminium silicate rocks, like granite. The rocks of the crust falls into two major categories- Sial and Sima. The crust is made up of two layers- an upper lighter layer called the sial (silicate + Aluminium) and a denser and heavy layer called sima (silicate + maganese). The average density of this layer is 3 gm\/cc.<\/p>\n

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MANTLE<\/strong><\/h4>\n<\/blockquote>\n

Earth’s mantle extends to a depth of 2,890 km, making it the thickest layer of earth. The mantle is divided into upper mantle or asthenosphere and lower mantle which are separated by the transition zone. The lowest part of the mantle is known as “D” layer. The mantle is composed of silicate rocks.<\/p>\n

\"\"<\/p>\n

The upper portion of mantle is called asthenosphere. It is in semi molten plastic state, and it is thought that this enables the lithosphere to move about it. Within the asthenosphere, the velocity of seismic waves is considerably reduced called ‘low velocity zone’.<\/p>\n

\n

CORE<\/strong><\/h4>\n<\/blockquote>\n

Beyond a depth of 2900 km lies the core of the earth. The outer core is 2180 km thick and is in the molten form. The inner core s 1220 km thick and is in plastic form due to the high pressure. It is made up of Nickel and iron (NiFe) and is responsible for earth’s magnetism. This layer has the maximum specific gravity. The temperature of the earth’s core is approx 6000 0<\/sup>C. It has the maximum specific gravity.<\/p>\n

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TEMPERATURE INSIDE THE EARTH<\/h4>\n<\/blockquote>\n

Temperature increase by 1 0<\/sup>C for every 32 meters of depth. For the first 100 km, there is 120<\/sup> increase per km. For the next 300 km, there is 20<\/sup> increase per km. After that, there is 10<\/sup> increase per km.<\/p>\n

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TRANSITION ZONES<\/h3>\n<\/blockquote>\n

All these layers are separated from each other through a transition zone. These transition zones are called discontinuities. There are 5 discontinities which are explained below:<\/p>\n

<\/p>\n

1- CONRAD DISCONTINUITY<\/h5>\n

It is a transition zone between upper continental crust and lower continental crust. This boundary is observed in various continental regions at a depth of 15 to 20 km. It is not found in oceanic regions. It is named after Victor Conrad.<\/p>\n

2- MOHOROVICIC DISCONTINUITY<\/h5>\n

It is a transition zone between lower crust and upper mantle. It is usually referred to as the Moho. It is named after Andrija Mohorovicic. The Moho separates both the oceanic crust and continental crust from underlying mantle. It lies almost entirely within the lithosphere.<\/p>\n

3- REPETTI DISCONTINUITY<\/h5>\n

It is a transition zone between upper mantle and lower mantle. It is defined as an increase in seismic velocities with depth. it was named after William C. Repetti.<\/p>\n

4- GUTENBERG DISCONTINUITY<\/h5>\n

It is a transition zone between lower mantle and outer core. It occurs within earth’s interior at the depth of about 2900 km, below the surface, where there is an abrupt change in the seismic waves that travel through earth. At this depth primary seismic waves(P waves) decrease in velocity while secondary seismic waves(S waves) disappear completely. The Gutenberg discontinuity was named after Beno Gutenberg. It is also referred as Oldham-Gutenberg discontinuity, or the Weichhert- Gutenberg discontinuity.<\/p>\n

5- LEHMANN BULLEN DISCONTINUITY<\/h5>\n

It is a transition zone between the outer core and inner core. It is an abrupt increase of P-wave and S-wave velocities at the depth of 220 km. It appears beneath continents, but not usually beneath oceans.<\/p>\n","protected":false},"excerpt":{"rendered":"

The internal structure of earth is layered in spherical shell: an outer silicate solid crust, a highly viscous asthenosphere and mantle, a liquid outer core that is much less viscous than the mantle, and solid inner core. The scientific understanding of the internal structure of earth is based on observations of topography and bathymetry, observations […]<\/p>\n","protected":false},"author":2,"featured_media":0,"comment_status":"open","ping_status":"open","sticky":false,"template":"","format":"standard","meta":{"footnotes":""},"categories":[40],"tags":[41],"class_list":["post-451","post","type-post","status-publish","format-standard","hentry","category-geography","tag-earth-interior-structure-of-earth-nife-sial-sima-gutenberg-discontinuity-conrad-discontinuity-lehmann-discontinuity-repetti-discontinuity"],"_links":{"self":[{"href":"https:\/\/old.sharedlearning.in\/dailyprep\/wp-json\/wp\/v2\/posts\/451","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/old.sharedlearning.in\/dailyprep\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/old.sharedlearning.in\/dailyprep\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/old.sharedlearning.in\/dailyprep\/wp-json\/wp\/v2\/users\/2"}],"replies":[{"embeddable":true,"href":"https:\/\/old.sharedlearning.in\/dailyprep\/wp-json\/wp\/v2\/comments?post=451"}],"version-history":[{"count":2,"href":"https:\/\/old.sharedlearning.in\/dailyprep\/wp-json\/wp\/v2\/posts\/451\/revisions"}],"predecessor-version":[{"id":456,"href":"https:\/\/old.sharedlearning.in\/dailyprep\/wp-json\/wp\/v2\/posts\/451\/revisions\/456"}],"wp:attachment":[{"href":"https:\/\/old.sharedlearning.in\/dailyprep\/wp-json\/wp\/v2\/media?parent=451"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/old.sharedlearning.in\/dailyprep\/wp-json\/wp\/v2\/categories?post=451"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/old.sharedlearning.in\/dailyprep\/wp-json\/wp\/v2\/tags?post=451"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}