Earth
is the third planet from the Sun and is the largest of the terrestrial
planets. The Earth is the only planet in our solar system not to be
named after a Greek or Roman deity. The Earth was formed approximately
4.54 billion years ago and is the only known planet to support life.
Facts about the Earth
Mass: 5,972,190,000,000,000 billion kg
Equatorial Diameter: 12,756 km
Polar Diameter: 12,714 km
Equatorial Circumference: 40,030 km
Known Moons: 1
Notable Moons: The Moon
Orbit Distance: 149,598,262 km (1 AU)
Orbit Period: 365.26 Earth days
Surface Temperature: -88 to 58°C
Composition and Structure of the Earth
The
Earth consists of four concentric layers: inner core, outer core,
mantle and crust. The crust is made up of tectonic plates, which are in
constant motion. Earthquakes and volcanoes are most likely to occur at
plate boundaries. The Earth is made up of four distinct layers:
1.
The inner core is in the centre and is the hottest part of the Earth.
It is solid and made up of iron and nickel with temperatures of up to
5,500°C. With its immense heat energy, the inner core is like the engine
room of the Earth.
2.
The outer core is the layer surrounding the inner core. It is a liquid
layer, also made up of iron and nickel. It is still extremely hot, with
temperatures similar to the inner core.
3.
The mantle is the widest section of the Earth. It has a thickness of
approximately 2,900 km. The mantle is made up of semi-molten rock called
magma. In the upper parts of the mantle the rock is hard, but lower
down the rock is soft and beginning to melt.
4.
The crust is the outer layer of the earth. It is a thin layer between
0-60 km thick. The crust is the solid rock layer upon which we live.
There are two different types of crust continental crust, which carries
land, and oceanic crust, which carries water.
Shape: The
shape of Earth approximates an oblate spheroid, a sphere flattened
along the axis from pole to pole such that there is a bulge around the
equator.
Chemical
composition: Earth's mass is approximately 5.97×1024 kg.It is composed
mostly of iron (32.1%), oxygen (30.1%), silicon (15.1%), magnesium
(13.9%), sulphur (2.9%), nickel (1.8%), calcium (1.5%), and aluminium
(1.4%), with the remaining 1.2% consisting of trace amounts of other
elements. Due to mass segregation, the core region is believed to be
primarily composed of iron (88.8%), with smaller amounts of nickel
(5.8%), sulphur (4.5%), and less than 1% trace elements.
Tectonic plates: The
mechanically rigid outer layer of Earth, the lithosphere, is broken
into pieces called tectonic plates. These plates are rigid segments that
move in relation to one another at one of three types of plate
boundaries: convergent boundaries, at which two plates come together,
divergent boundaries, at which two plates are pulled apart, and
transform boundaries, in which two plates slide past one another
laterally. Earthquakes, volcanic activity, mountain-building, and
oceanic trench formation can occur along these plate boundaries.
Surface: Earth's
terrain varies greatly from place to place. About 70.8% of the surface
is covered by water, with much of the continental shelf below sea level.
This equates to 361.132 million km2 (139.43 million sq mi). The
submerged surface has mountainous features, including a globe-spanning
mid-ocean ridge system, as well as undersea volcanoes, oceanic trenches,
submarine canyons, oceanic plateaus and abyssal plains. The remaining
29.2% (148.94 million km2, or 57.51 million sq mi) not covered by water
consists of mountains, deserts, plains, plateaus, and other landforms.
Magnetic field: The
main part of the Earth's magnetic field is generated in the core, the
site of a dynamo process that converts kinetic energy of fluid
convective motion into electrical and magnetic field energy. The field
extends outwards from the core, through the mantle, and up to Earth's
surface, where it is, to rough approximation, a dipole.
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