The Planet Earth

Earth is a unique planet between the solar system at least that is because:

Figure(1) Earth.

Earth is a unique planet between the solar system at least that is because :
-Earth has a thick atmosphere, which protect Earth’s residents from harmful UV rays from the sun
-Earth"Atmosphere contains enough oxygen that allows it to support life, and it has the perfect amount for fires to burn.
- Earth also has large amount of liquid water which play an important role in regulating of earth climate.
Earth also has a strong magnetic field that protects it from harmful solar wind and solar flares.
Earth is the suitable distance from the sun. If Earth were farther away, it would be too cold, and all the water would freeze. If Earth were closer, the water would be boiled off.
All these factors together allow Earth to be the only planet -that known -that can support life
Now let’s learn more about the component of our unique planet .

Earth’s Different Spheres .

Earth as a System consists of has five different spheres in briefly they are:

figure(2) Earth as a System consists of has five different spheres

1- the Atmosphere:
The gaseous envelope around the earth is known as atmosphere; it is held down by Earth’s gravitational pull. The atmosphere is concentrated at the Earth’s surface and rapidly thins as you move upward, blending with space at about 100 miles above sea level. The atmosphere is actually very thin compared to the size of the earth.. The heat trapping ability it has helps to keep the Earth warm enough for life, and it also protects the Earth from harmful solar radiation and cosmic rays
Composition of the Atmosphere:
The atmosphere is composed of a mixture of many different gases. Nitrogen accounts for 78% of the atmosphere, Oxygen 21% Argon 0.9%. Small amount of Gases like carbon dioxide, nitrous oxides, methane, and ozone that account for about a tenth of one percent of the atmosphere. Water vapor is unique- its concentration varies from 0-4% of the atmosphere depending on where you are and what time of the day it is.

2-The Hydrosphere:
The Hydrosphere includes all the waters of the seas and oceanic basins, rivers and lakes that cover about 72% of the total surface area of the Earth, including the underground water which fills the pores in rocks and soil in the ground The hydrosphere surrounds the Earth from all sides forming what is known as sea level which is internationally recognized and all heights of different topographical features are attributed to such as mountains, plains, plateaus, valleys and others features that forming the rocks of earth’s crust.

Figure(3)Hydrosphere

3-The Geosphere:
The solid part of the Earth (rocks, minerals, soil, etc.), Most of the geosphere is below the surface.
-How do we learn about interior composition of the Earth?
They study the Earth’s interior by seismic waves. Same waves that are caused by earthquakes and they measured changes in speed/direction of seismic waves.From this, they found that Earth is layered, and have hypothesized about what those layers consist of.

Figure (4) Earth’s Interior Layers

-The Crust
•The outermost layer of Earth vary in thickness.
earth crust consists of three types of rocks (Igneous- Sedimentary-Metamorphic).
–Thickest under mountain ranges (70 km – 40 miles).
–Thinnest under mid-ocean ridges (3 km – 2 miles).
•The Mohorovičić discontinuity or “Moho” is the lower boundary which Separates the crust from the upper mantle. known by a change in the velocity of seismic P waves.
we have two types of Crust: continental and oceanic .Crustal density controls surface position.Continental crust Less dense than Oceanic crust
Chemical composition of crust:

Table ( 1 ) Chemical composition of earth crust.

The Mantle:
Solid rock layer between the crust and the core.
About 2900 km thick, the mantle is 80% of Earth’s volume.
It is composed of iron, magnesium and silicon
Oxides in the form of solid rocks except the upper part of the mantle (Asthenosphere) Below ~100-150 km with a thickness reaches about 350 km the rock is hot enough to flow to form giant convection currents which permits the drifting of the continents above.
Using seismic waves helped scientists to divide mantel into three subdivisions: upper, transitional, and lower
The Core:
The core is the innermost zone of Earth with a radius of about 3486 km. It forms about one sixth (1/6) of the Earth by volume, but being composed of materials with very high density, it makes about one third (1/3) of the Earth by weight. The pressure there is very high reaches about millions of the atmospheric pressure and the temperature is more than 5000°C. The studies that obtained by scientist when they analyzed the seismic waves that spread through the Earth’s zones during the occurrence of earthquakes helped greatly in determining that the earth’s core could be divided into two parts.
Outer Core:

with a thickness about 2100 km and consisting mainly of molten iron and nickel and stands under a pressure of 3 millions atmospheric pressure and with a density reaches about 10 gm/cm3.
Inner Core:
Consisting of rocks of very high density about 14 gm/cm3 and with a radius of 1386 km. Thus, scientists were able to explain the origin of the magnetic field of Earth may be generated from the presence of outer core that composed of molten material revolves around the rocky solid inner core

Figure(5)Flow in the outer core generates the magnetic field.

4-Cryosphere
When scientists talk about the cryosphere, they mean the places where water is in its solid form, frozen into ice or snow.in other words cryosphere is the icy portion of Earth’s crust includes glaciers, permafrost and ground ice, polar ice caps and frozen polar seas

figuer (6 ) Cryosphere

5-Biosphere :
Earth’s Ecosystems which found on Earth’s surface and subsurface to depths of a few kilometers Life occupies an extreme range of environments and strongly interacts with the atmosphere, the hydrosphere and the solid earth (these interactions are called ecology)

Geopatra