Earth is somewhat like chicken egg. Earth's hard layer is like egg shell. Egg white is like mantle and yolk of egg is like core of Earth. Volcanic eruption brings out material from the mantle.
Earthquake and waves
Earthquake is any sudden movement in the Earth which releases energy. This energy Travel in waves in spherical manner. The wave created at the location of earthquake are called earthquake wave.
Hypocenter or Focus: Place where the earthquake takes place, or from where the energy is released. This wave from the hypocenter travels throughout the body of earth. Waves generated at Hypocenter is called Bodywave.
Epicenter: It is the point where the body wave hits vertically above the Hypocenter. At the Epicenter one more wave is created called the Surface wave which travel only on the surface of Earth. Every living being is located on the Earths surface, hence the destruction on the Earth surface is caused by Surface wave.
Characteristics of wave
There are two type of waves called P-wave and S-wave.
Medium Property:
- S wave: Travel only in solid Medium.
- P wave : Travel in solid, liquid, gas.
Refraction property:
- S wave and P wave : Refract when density of medium changes.
Speed Property:
- S wave and P wave: Change speed with change in density of medium.
Observation
S-wave does not emerge on the surface of the Earth in the region beyond 105 degree with respect to the Hypocenter and Earth's center. This region is also called S-wave Shadow zone. S-wave is not observed here.
P wave did not emerge on the surface of earth in the region beyond 105 degree upto 145 degree. It is known as P wave shadow zone, here P wave is not observed.
These S wave cannot travel on liquid, hence there must be a liquid inside earth i.e Core. Angle is always 105 degree, this means that core inside Earth is in Uniformly spherical shape. Hence core is a liquid uniform sphere. So the wave which entered the core died and other wave emerged out.
P wave can travel in any medium i.e solid, liquid, gas. When it passed through the core, the medium got changed from solid to liquid and emerging out from liquid to solid, this resulted in refraction of P wave at an angle of 145 degree. Hence it did not emerge in p wave shadow zone i.e belt between 105 degree and 145 degree.
Chemical Composition
The Earth crust mostly constitute of Silica and aluminium and its oceanic thickness is around 5 km and continental thickness is around 30 km to 40 km and mountainous thickness is around 70 km.
Mantle of Earth mainly constitute of Silica and magnesium and its thickness is around 2900 km. The core of Earth mainly constitute of Nickle and Iron and its thickness is around 6400 km.
Physical Composition
The top solid part of mantle i.e crust + top layer of mantle together is known as Lithosphere.
The middle part of the mantle also called the plastic mantle as it is not solid and not completely liquid is know as the Asthenosphere. Magma convection takes place in Asthenosphere, it is upto 400 km below. The lower most part of mantle is called Mesosphere, where the solid part of mantle is situated.
The Earth's core is also divided into two part. The outer part of core is in liquid form and called upper liquid core. The inner core is in solid form and called lower solid core.
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