Atmosphere:

Atmosphere is a layer of gases that surrounds the Earth and is held together by the Earth’s gravity. It consists of roughly 78% nitrogen and 21% oxygen, with water vapor , carbon dioxide and other gases .It is 8Km thick ,with variations through out the surface of Earth.

Besides the air we breathe, atmosphere provides a greenhouse effect, blocking out the harmful elements of the Sun’s rays which is ultraviolet solar radiation.

Atmosphere also transports water vapor causing rain and moderates the Earth’s temperature. The heating and reheating of air causes shifting of hot and cool air called atmospheric circulation. This circulation is what causes shift in weather and climate.

Without atmosphere’s effect of green housing and temperature control, the Earth would be -18⁰C making the life impossible.

Season:

Changing seasons are caused by the Earth’s movement. The Earth completes a rotation on its axis in a day and takes a year to complete a revolution of the sun.

These two movements create variation in temperature, weather and seasons. The distance of the Sun is 146 million Km from the Earth and the Earth temperature varies between -89⁰C to 57.7⁰C.

During the rotation the part of the Earth’ surface facing the Sun, experiencing midday while the other side of the Earth ha a cool night.

The Earth is inclined at an angle of 66.5⁰.

During the first half of the year, the Northern hemisphere is closer to the Sun, and experiences summer, while the Southern hemisphere experiences winter. In the second half, the axis of the Earth tilts the other way and the Southern hemisphere faces the Sun, thus experiencing summer.

Earth

The earth is the third planet from the sun, the fifth largest planet and the densest major body in solar system. It is the only planet known to have life. In proportion to its size it as largest moon in the solar system.

The word Geography (Ge means Earth in ancient Greek and grapy means writing) which means study of all the natural and human aspects of earth.

Earth is one of the four solar Terrestrial planets .Planets with a rocky body rather than gases are called terrestrial planets. Jupiter is a gas planet.

Chemical composition:

The mass composition of earth is approximately 5.98*1024kg.

It is made up of approximately 100 elements of which iron, oxygen, silicon, magnesium, sulphur, nickel, calcium and aluminum are the main constituents.

Shape:

Earth is a sphere lightly squished at the poles and bulging at the Equator. So if you drew a line across the Equator, and a line between the poles, the line around the Equator would actually be 43Km longer.

Therefore Earth is not a perfect sphere and is termed on

Oblate spheroid. This is caused by rotation of Earth.

That average diameter of Earth is 12,742Km.

Internal Structure of Earth:

Plate Tectonics:

The outer layer of Earth called Lithosphere,is broken into vast pieces known as tectonic plates. These plates are at the same place, but shift at the boundaries, causing earthquakes, volcanic activity, and Mountain building and trench formation under the sea. The Himalayas are the best example for mountain building.

Surface:

About 70.8% of the Earth’s surface is covered in water. There is a lot of physical features in this submerged surface, such as longest mountain ranges in the world, volcanoes, trenches, canyons, oceanic plateaus and plains. This is known as Hydrosphere.

The remaining 29.2% is covered in mountains, deserts, plains, plateaus, and other features. This surface undergoes constant changes due to the effect of plate tectonics and erosion.