Science

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Surface and Interior of Earth
Earth, the largest and densest rocky planet, was formed about 4.5 billion years ago. The Earth's [|interior] is divided into four layers, which is typical of rocky planets. Each layer has different characteristics and is made of different [|elements] and minerals. There are many different types of features on Earth’s surface due to the complexity of our planet. The [|surface] is unique from the other planets because it is the only one which has liquid water in such large quantities. Water forms some features of Earth's surface such as rivers, oceans, beaches and lakes. Other [|surface features], such as mountains, [|earthquakes] and volcanoes, are formed when large pieces of the Earth’s outer layer move slowly by [|plate tectonics].
 * || [[image:http://www.windows2universe.org/earth/images/earth_s2.gif link="http://www.windows2universe.org/earth/images/earthafr_image.html"]] ===== Click on image for full size //Image courtesy of NASA/JPL// ===== ||