Shells of earth By Abdul Qahar

TopicThe Structure of the Earth

Presented To: Sir Shahroz Khan Presented By: Abdul Qahar

&Naveed Akhtar

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.

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.

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

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)

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.

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.

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).

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.

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.

The Crust

• This is where we live!

• The Earth’s crust is made of:

1. Continental Crust

2. Oceanic Crust

Continental crust

• The thicker crust is continental crust, which is less dense and composed of (felsic) sodium potassium aluminium silicate rocks, like granite.

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.

Crust• The crust ranges from 5–70 km (~3–44 miles)

in depth and is the outermost layer.