Structure of the Earth


 The earth is made of rocks; we cannot dig much deeper about 10 km, our knowledge of structure of the earth is derived from the study of seismic wave. The velocity of these waves depends on the composition of the region through which they travel. So by determining the velocity of the waves, we can infer the composition of the region through which they pass. The earth has multiple layers are crust, mantle and core.


Structure of the Earth

Crust:

      This is the outermost rocky layer. The rocks consist mainly of silicates; they are compounds of silicon with silicon oxide as the basic compound. The thickness of crust is about 50 km under the continent. The thickness of crust is not same everywhere. Under the seafloor, its thickness is much less.

Internal Structure of the Earth

Mantle:

       The layer from 50 km to the depth of about 3000 km is called the mantle. It is rich in iron and magnesium silicates.  

Core:

      The innermost layer of the earth is called core. It is divided into two regions. The inner core is solid metal sphere radius about 1200 km. It is almost pure iron alloy with small amount of nickel. The inner core is surrounded by liquid metal about 2200 km.  The matter here is in the fluid state. The movement of inner core is responsible for earth magnetic field.

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Different Types Of Movement Of The Earth's And Their Effects

Following are the different types of the Earth movement:

Orbital motion:


The earth revolves around the sun in a particular path called its orbit. It takes 365.25 days to complete it path around the sun. The earth year is 365 days long and extra 0.25 days added after every fourth year.
Different types of movement of the earth's and their effects

The shape of orbit is not circular, it like an oval shape. The distance from sun varies during the motion. The earth is closest to the sun in January about 91.4 million miles. It is farthest away from sun in July about 95 million miles.

Axial motion:


Axial motion of the earth's and their effects


The earth is also rotating on it axis west to east and take 24 hours to complete round on it axis. The side of earth that faces the light of the sun has day time and the other side of earth has night time.


Why different seasons on the earth?


The earth axis is tilted slightly at angle 23.5°. Due to this position it gives us four seasons (summer, spring, winter and autumn). The sun rays hit different portion of earth differently depending upon position of earth during it orbital motion.

Orbital motion and their effects on Seasons of the earth's


 The earth position is so that it tilted slightly toward sun (from June to august). The sun rays hit directly on northern hemisphere result summer in this region and winter in southern hemisphere.

The earth position is so that it tilled slightly away from the sun (from December to February). The northern hemisphere is little away from the sun. The sun rays hit less directly result winter in this region and summer in southern hemisphere. There is no difference between summer and winter close to the equator.

The earth position is so that the sun shines equally on both hemispheres (from September to November). The result is autumn in northern hemisphere and spring in other region.


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