9A -LITHOSPHERE-EARTH'S STRUCTURE

LITHOSPHERE

Where are we now and where are we going?

“…in every grain of sand there is the story of the earth.”
Rachel Carson

At the most basic level, humans depend upon the earth:Atmosphere…air to breathe
Hydrosphere …water to drink
Lithosphere …food to eat
Biosphere …food to eat

We need to be able to understand past transformations and predict future transformations. If we can forecast weather, why can’t we “earthcast” changes in the Critical Zone?
Earth – more than 5,000 million years old and is still in the process of changing.

In one year, Atlantic Ocean widens by 10cm while Pacific Ocean is shrinking as the continents move slowly across the globe.
Red Sea – in its infancy – in 60 million years time it will be as wide as the Atlantic Ocean
Africa and Asia may split apart as a result of the Mediterranean merging with Atlantic Ocean

EARTH COMPRISES:

3 main regions
1.Lithosphere – solid, inorganic section
2.Hydrosphere – liquid section
3.Atmosphere – gaseous section

THE INTERIOR OF THE EARTH

The Earth is divide into 3 concentric layers
•The crust
•The Mantle
•The core
Each layer has different properties

Earth's Crust Diagram:This diagram shows the various parts of the upper mantle and crust. The crust can be continental or oceanic. The lithosphere is solid and consists of the crust and uppermost mantle. The asthenosphere is below the lithosphere and is a plastic, moving part of the upper mantle. The lithosphere slides upon the moving asthenosphere in the theory of plate tectonics.

This diagram shows a cross-section of the Earth. It includes from the outer surface inward: the crust, mantle, outer core and inner core.

THE CRUST

The earth’s uppermost part.
The crust is a very thin skin which surrounds the planet
The Earth's Crust is like the skin of an apple.
It is very thin in comparison to the other three layers.
From the ocean floor towards the interior it extends upto 10 km.
It includes igneous, sedimentary and metamorphic rocks.
From the earth’s surface it extends from 40km to 60km depth.
The temperatures of the crust vary from air temperature on top to about 870 degrees Celciusin the deepest parts of the crust.
You can bake a loaf of bread in your oven at 350 degrees Fahrenheit , at 1600 degrees F. rocks begin to melt.
* The crust of the Earth is broken into many pieces called plates. The plates "float" on the soft, plastic mantle which is located below the crust. These plates usually move along smoothly but sometimes they stick and build up pressure. The pressure builds and the rock bends until it snaps. When this occurs an Earthquake is the result!
* Notice how thin the crust of the Earth is in comparison to the other layers. The seven continents and ocean plates basically float across the mantle which is composed of much hotter and denser material.
* The crust id divided into two layers: sial and Sima
* SIAL: uppermost portion of the crust. It is not found below the ocean floor.
*SIMA: lower part of the earth’s crust is Sima .

SIAL:
Topmost layer consists of granitic rocks
On an average forms the first 25 km of the crust and is lighter
Consists of silicates and aluminium, and other ligher metals.
SIAL – SI – Silicate; AL-aluminium
Sial layer is thick over the continents but is thin or absent on the ocean floors.

SIMA -
Below the Sial layer is a denser layer on an average 35 km.
Consists of silicates of magnesium, iron and other denser metals .

Why is the composition of the crystal layer of earth of great interest?
We get most of our minerals from the Crust of the earth.
Valuable soil layer – essential for the growth of both cultivated and wild plants.
Physical features of the earth’s crust influence land use and other human activities.
Density of human population also depends on nature of the relief features in an area.

Mesosphere or The Mantle
* It is between the crust and the core. It is mainly solid, but acts as a

fluid-like solid.
*The imaginary line which separates the lithosphere from the mantle is known as “Moho’
* The upper part of the mantle is cooler and so stronger. This strong

part of the mantle is joined together with the crust to form the

lithosphere. It goes down to 1300˚C.
* The mantle which directly underlies the lithosphere is much hotter and

so weaker, this is called the Asthenosphere. (astheno means weak) it

goes down to 1700 ˚C . The lithosphere slides over the Asthenosphere.

The area below the this is called the lower mantle * Convection currents in the mantle
* We think the mantle acts like hot and sticky tar.
* It is heated by the core below it and cooled by the crust above.
* When you heat a fluid it’s density drops and it expands. If you cool it, it will contract and become more dense. So the hotter material at the base rises toward the top while the cooler material at the top sinks. This generates slowly flowing convection currents in the Mantle

* Has an average thickness of about

2,840 km
* Consists of mixed silicates and

metals like magnesium and iron and

is rich in olivine

UPPER MANTLE OR ATHENOSPHERE

* Is partially in molten state.
* Velocity of the earthquake waves decreases in it
* Lower Mantle is called the Mesosphere.
* Temperature of this layer is very high
* Between 850 degree C in upper region and 2208 degree C in lowest region

Barysphere or The Core

•Innermost layer of the earth – extends from below the mantle to the central part of the earth.
•On the basis of earthquake waves, this core is divided into two parts
1. outer core which is liquid
2. inner core or Nife which is solid
* The core is made up of mainly iron and nickel which makes it very dense
* The movement of the liquid outer core generates the Earth’s magnetic field
* Outer core is 2250 km thick and surrounds the Inner Core.
* It is till in molten condition
* Inner core is also called ‘Nife’ because it consists of Nickel and iron.
* Its thickness is about1228 km.
* It is very hard in nature.
* It is a compound of alloys of carbon, iron or silicon.
* Due to high temperature, nickel and iron are found in molten stage.
* Liquid iron generates its own electricity and so under pressure, the core is the source of the earth’s magnetic field.
* Has a radius of about 3,500 km
* Consists mostly of metals - mostly iron and nickel – hence known as Nife (Ni-Nickel, Fe-iron)
* Temperature – about 5000 degree celcius
* Divided into INNER CORE AND OUTER CORE
* Outer core behaves lke liquid and does not allow earthquake waves to pass through it.
Greatest depth reached by human beings into the earth’s crust is 8 km for drilling oil.

The interior of the Earth has a major impact on other Earth systems.

•Convection currents in the mantle cause the movement of the plates
•The internal heat is responsible for volcanoes.
•The outer core generates the Earth’s magnetic field
•Earth’s early atmosphere and water was probably formed from volcanic gases derived from inside the Earth.
•The position of the continents effects ocean currents and so the Earth’s climate.
•Plates also effect the geographic distribution of organisms and so their evolution.

What is the solid earth made of?
Planet Earth is a rocky planet. It is made up of rocks and minerals.
The Earth is made up of a number of Elements
The interior of the Earth is quite different than the exterior (continental crust)

LAYERS OF THE EARTH


* Crust

* Mantle

* Outer core
* Inner core