The Earth
Earth is the third planet from the Sun and the fifth largest planet in our solar system. It has a diameter of 12,756 km, a mass of 5.9736 kg, and an orbit of 149,600,000-km (1.00 AU) from the Sun. The Earth is also the densest major body in the solar system.
Interior:
The Earth's interior is made up mostly of rock and metal. It is divided into four main layers. These layers are:
The inner core: a solid metal made up of nickel and iron.
The outer core: a liquid molten core of nickel and iron.
The mantle: a mostly solid and dense material made of silicate rock.
The crust: a thin material made of silicate rock.
Plate tectonics:
Unlike the other terrestrial planets, Earth's crust is divided into several separate solid plates that float around independently on top of the hot mantle below. This is called plate tectonics. Two major processes characterize it: spreading and subduction. Spreading occurs when two plates move away from each other and new crust is created by upwelling magma from below. Subduction occurs when two plates collide and the edge of one dives beneath the other and ends up being destroyed in the mantle. Currently, there are eight major plates. They are:
The North American Plate: North America, western North Atlantic and Greenland
The South American Plate: South America and western South Atlantic
The Antarctic Plate: Antarctica and the "Southern Ocean"
The Eurasian Plate: eastern North Atlantic, Europe and Asia except for India
The African Plate: Africa, eastern South Atlantic and western Indian Ocean
The Indian-Australian Plate: India, Australia, New Zealand and most of Indian Ocean
The Nazca Plate: eastern Pacific Ocean adjacent to South America
The Pacific Plate: most of the Pacific Ocean and the southern coast of California
There are also twenty or more small plates such as the Cocos, Arabian, and Philippine Plates. Earthquakes are much more common at the boundaries of these plates.
Magnetosphere
The Earth has two poles (north and south ) that act as magnets. This creates a magnetosphere around the Earth. A magnetosphere is a magnetic field surrounding an object. The magnetosphere around the Earth is caused by electric currents generated from its inner core. It is responsible for causing solar winds and auroras. The sun and the other planets too but Earth has the strongest. Also, the Earth's poles reverse every 200,000 to 300,000 years.
Surface:
Seventy percent of Earth's surface is covered with water, and the other thirty percent makes up the seven major continents. (Asia, North America, Australia, Africa, South America, Europe, and Antarctica) These continents were connected as one large land mass over 250 million years ago but the shifting continental plates caused them to break up and spread apart.
Atmosphere:
An atmosphere surrounds the Earth. It protects the planet by blocking dangerous rays from the Sun. The atmosphere is a mixture of gases that is thickest near the surface but eventually thins until it merges with space. It's made up primarily of nitrogen (78%), Oxygen (21%), and some other various gases (1%). The atmosphere has five layers. They are:
The troposphere: the first layer above the surface. Most of the Earth's weather occurs in this layer.
The stratosphere: where the ozone layer is. It absorbs the Sun's harmful rays here.
The mesosphere: most meteors burn up in this layer.
The thermosphere: where space shuttles orbit. It is also where the auroras and meteors are.
The exosphere: a thin layer where space and the atmosphere merge.
Satellite:
The Earth has only one natural satellite, the moon. It does, however, have thousands of man-made satellites and a complicated relationship with an asteroid called Asteroid 3753 (1986 TO). It is called a companion to the Earth.