User:Cadillac000/TWA/Earth/2

Donee below. The crust is split up into parts called plates. These plates interact as they move about causing earthquakes and creating volcanoes and mountain ranges. The place where plates meet are called plate boundaries. There are three types of plate boundary: constructive, destructive and transform.

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 urbanisation — the growth of cities. Many things can change the surface of the Earth. Plate tectonics is main cause of change but there are others such as erosion from wind and rain, erosion by the oceans or meteorite impacts. There are three main types of rock that make up the Earth's surface: Igneous rock is made when magma or lava from the mantle reaches the surface and cools. As it gets colder it turns into rock or solidifies. Sedimentary rock is made from sediment, like sand or small bits of other rock, that has been crushed and packed tightly together. Metamorphic rock which is made when either of the other two types are changed by high or low temperatures and pressures.

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.

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.

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.