User:Frozenfire71/TWA/Earth/2
The Earth is the third
The Earth is home to millions of species of
. Earth has many places that are suitable for humans to live in, although some areas of the planet can are dangerous or uninhabitable.Science shows that Earth formed around 4.5 billion years ago. The
71% of Earth's surface is covered in salt water
Earth interacts with other objects in the Solar System, particularly the Sun and the
Shape and structure
Earth is a terrestrial planet. This means it is made up of solid rock unlike a
Inside, the Earth is similar to the other terrestrial planets. It has an outer, solid rock layer called the
Tectonic plates
The Earth is the only terrestrial planet with
Surface
The Earth changes greatly from place to place. Over 70% of the Earth surface is covered by water. The underwater surface has many of the same features as the above sea with volcanoes, mountains and trenches or canyons. The 30% not covered by water is mostly forests, deserts plains, mountains and plateaus. Human civilization has led to increasing
Atmosphere
A planet's atmosphere is a layer of different gases surrounding it. It is kept there by gravity. The Earth's atmosphere is made of about 78% nitrogen, 21% oxygen and small amounts of other gases. This mixture is often called air. Further up there is a layer of ozone gas called the Ozone layer. Ozone absorbs ultraviolet radiation from the Sun. Ultraviolet radiation is dangerous to people, so without the Ozone layer life would not be possible. The atmosphere also protects the earth from crashes with meteors and small asteroids. This is because they burn up due to all the friction as they fly through it. It also helps to keep Earth warm. Some gases including carbon dioxide and methane act like a blanket around the Earth, they trap heat under them, keeping the Earth warm.[6]
Weather, climate, and water cycle
Hot air rises. As it rises it gets colder again and falls. This creates convection currents. When hot air meets cold air different weather effects happen. Convection currents are the cause of almost all weather on Earth. When it gets hot on the surface water evaporates and becomes steam or water vapour. This hot water vapour rises. As it rises it gets colder. When it gets cold enough it turns back into water again. This causes the clouds and rain. It is called the water cycle.[7]
Orbit and rotation
The Earth takes about 24 hours to complete one day and about 365 days to complete a year. Actually, the Earth take 365.24 days to revolve around the sun. After every four years, an extra day is added, and the year has 366 days. This is a leap year. The Earth is, on average, 150 million kilometers away from the Sun, and moving at a speed of 30 kilometers a second or 108,000 miles an hour. The Moon orbits the Earth at an average distance of 250,000 miles. It is tidally locked to Earth, which means it always has the same side facing the Earth. It takes roughly one month to complete one orbit. The Earth is part of the Solar System and orbits the sun along with thousands of small objects and eight planets. The Sun, and therefore the Solar System, are currently traveling through the Orion Arm of the Milky Way Galaxy and will be for approximately the next 10,000 years.[8]
References
- ^ Gnawledge, O'penn. "Planet Earth in the Balance of History". Science and Nature Journal. SandNjournal.com/Earthinthebalance. March 21, 20. Retrieved April 24th, 2013.
- ^ "Origin of the Moon and Earth". Reisch, Maggy. Nature.com: Volume 10:2, p.19-27. http.www.nature.com/102/Reisch/Earth. Retrieved 2009-07-28.
- ^ "Tectonic plates. Shifting Sands". Roberts, Paul. Harvard University Press. http.www.harvard.edu/roberts/shifting. Retrieved 2009-07-28.
- ^ Toshiro Tanimoto. "Crustal of the Earth". American Geophysical Union. Retrieved 2009-08-02.
- ^ "The Crust". Alphonz, Edgar. Oregon State University. http.www.osu.edu/Alphonz/Crust. Retrieved 2009-07-03.
- ^ "NASA - Earth's atmosphere". NASA Student Guides. http.www.nasa.gov/student/atmosphere. Retrieved 2009-08-06.
- ^ "What causes weather?". NASA Student Guides. http.www.nasa.gov/student/weather. Retrieved 2009-08-06
- ^ "Earth's in the Milky Way". NASA Student Guides. http.www.nasa.gov/student/milkyway. Retrieved 2009-08-06.