Structure and Composition of the Earth

GEOPHYSICS

 Geophysics:  Is the branch of science that is concerned with the physical, chemical, geological, astronomical and other characteristic properties of the earth.

OR

Is the study of the physical properties of the earth.

  

INTERIOR STRUCTURE OF THE EARTH

The structure of the earth is composed of three major zones arranged in a concentric manner.

            i.  The crust

            ii.The manner

            iii. The core

THE CRUST

Is the outer solid layer of the earth. It is the thinnest layer compared to other two components. Its thickness is as out 6 to 40 km (5 to 30 miles) compared to the radius of the Earth 6400 km.

TYPES OF CRUST

                         i.   Continental crust (SIAL)

                         ii.   Oceanic crust (SIMA)

CONTINENTAL CRUST (THE SIAL)

Is the outer most layer of the earth which forms the continents. The SIAL composed of silica and Aluminium compound.

 Seas, oceans, rivers and lakes are interrupts SIAL.

OCEANIC CRUST (THE SIMA)

Is the inner part of the crust it is composed by silica and magnesium. It is denser than SIAL.

The SIMA forms the oceanic floor.

The SIAL and SIMA is separated by layer called²Conrad discontinuity”

THE MANTLE

Is the layer found between the earth’s crust and the core. It extends to a depth of 2900km below the earth’s surface from the Mohorovic discontinuity. It is denser than earth’s crust.

The layer which separates the crust and mantle is called Mohorovic Discontinuity”

The Mantle contains about 70% of the Earth’s mass.

PARTS OF MANTLE

         i.   The upper Mantle

       ii.    The lower Mantle

The temperature of the upper Mantle is about 870°C and increases to 2,200°C of the inner (lower) mantle.

The Mantle is composed by rocks that are said to be in a plastic state.

THE CORE

Is the inner most part of the Earth’s interior.

Have two layers

         i.     Liquid outer core

       ii.    Solid inner core

 LIQUID OUTER CORE

The layer composed of a liquid of molten nickel and iron called MAGMA. It extends to a depth about 5000km below the earth from the Mantle.

SOLID INNER CORE

The layer composed of a solid of iron – nickel alloys. It is solid because of the high pressure, the inner core is very hot, and its temperature is about 6000°C.

The layer which separates the Mantle and the core is called. “Gutenberg discontinuity”  

TECTONIC PLATES

Are huge pieces creates by cracks of the earth’s crust and part of the Mantle.

They float on top of the semi- Molten rocks underneath. They move about at a very slow speed.

These Tectonic plate movements have split the continents.

BOUNDARY

Are lines where two tectonic plates meet.

TYPES OF BOUNDARIES

         i.     Destruction boundaries.

       ii.     Constructive boundaries.

     iii.    Conservative boundaries.

DESTRUCTIVE BOUNDARY

Is the boundary found at edges of two plates moving towards each other.

CONSTRUCTIVE BOUNDARIES

Are boundaries formed at the edges of two plates moving away from each other.

  

CONSERVATIVE BOUNDARIES

Are boundaries formed when two plates slides past each other without moving a part or towards each other.