shells of earth by abdul qahar
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TopicThe Structure of the Earth
Presented To: Sir Shahroz Khan Presented By: Abdul Qahar
&Naveed Akhtar
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Structure of the Earth
• The Earth is made up of 3 main layers:
– Core
– Mantle
– Crust
Inner core
Outer core
Mantle
Crust
The interior structure of the Earth is layered in spherical shells, like an onion.
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Structure
• The structure of Earth can be defined in two ways:
1. Mechanical properties such as rheology,
2. Chemically.
• Mechanically, it can be divided into lithosphere, asthenosphere, mesospheric mantle, outer core, and the inner core.
• Chemically, Earth can be divided into the crust, upper mantle, lower mantle, outer core, and inner core.
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DepthLayerKilometres Miles
0–35 0–22Crust (locally varies between 5 and 70 km)
35–60 22–37Uppermost part of mantle
35–2,890 22–1,790 Mantle
2,890–5,150 1,790–3,160 Outer core
5,150–6,360 3,160–3,954 Inner core
Physical Description
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Core
• Discovered in 1936 by Inge Lehmann.
• Temperature is 6,000 degrees Celsius (10,832 F).
• Outer core: 1,380 miles (2,200 kilometers)
• Inner core: 780 miles (1,300 kilometers)
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Core• The INNER Core - is solid (because of EXTREME pressure
from everything above it)
• The core is thus believed to largely be composed of iron (80%), along with nickel and one or more light elements, whereas other dense elements, such as lead and uranium.
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Seismic measurements of core
• Core is divided into two parts:
• “Solid" inner core with a radius of ~1,220 km
• Liquid outer core radius of ~3,400 km.
• Densities are B/W 9,900 and 12,200 kg/m3 in the outer core and 12,600–13,000 kg/m3 in the inner core.
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Mantle• Temperatures is B/W 500 to 900 °C (932 to 1,652 °F)
at the upper boundary with the crust; to over 4,000 °C (7,230 °F) at the boundary with the core.
• Depth is 2,890 km, making it the thickest layer of Earth.
• The pressure at the bottom of the mantle is ~140 GPa (1.4 Matm).
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Mantle• Because of the temperature difference between the
Earth's surface and outer core and the ability of the crystalline rocks at high pressure and temperature to undergo slow, creeping, viscous-like deformation over millions of years, there is a convective material circulation in the mantle.
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Mantle composition• It has all the properties of a SOLID but can
flow very slowly just beneath the crust.• Here it is made of MAGMA – very thick and
sticky molten rock.• The mantle is composed of silicate rocks that
are rich in iron and magnesium.
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The Crust
• This is where we live!
• The Earth’s crust is made of:
1. Continental Crust
2. Oceanic Crust
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Continental crust
• The thicker crust is continental crust, which is less dense and composed of (felsic) sodium potassium aluminium silicate rocks, like granite.
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Oceanic crust
• The thin parts are the oceanic crust, which underlie the ocean basins (5–10 km) and are composed of dense (mafic) iron magnesium silicate igneous rocks, like basalt.
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Crust• The crust ranges from 5–70 km (~3–44 miles)
in depth and is the outermost layer.
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