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The Earth formed approximately 4.6 billion years ago. The Earth was formed at the same time as the rest of the solar system by the coming together of materials that were not incorporated into the sun. The Earth was very hot (perhaps molten) at first, but then cooled off. When the planets began to form, earth transforms from random mix to layered sphere. The layers differ physically and chemically. They are separated by their density. Three main layers where formed. 1) Core – center of the earth 2) Crust – Outer layer 3) Mantle – separates core and crust Core: Core consists of mostly nickel and iron. These are very dense elements. Inner core (6400 KM to 5200 KM) is solid. Outer core (5200 KM to 2900 KM) is molten. Mantle: These are intermediate density elements – mostly oxygen, magnesium, iron, silicon. It’s depth range from 40 KM to 2900 KM. Crust: These are “scum” on top of mantle soup. They contain lowest density elements – silicon, aluminum, iron, calcium, magnesium, sodium, potassium combined with oxygen. Their thickness ranges from 5 KM to 40 KM. Interesting Fact:
Oceans appeared very early and have been on the surface continuously ever since. Liquid water appeared on the Earth's surface starting around 4 billion years ago. For the first 600 million years, the Earth's surface was too hot for liquid water to have existed on the surface. Water vapor was released from the abundance of volcanoes, from comets (composed largely of ice and organic compounds), and meteors (also possessing organic compounds). As the water vapor condensed, fell to the Earth's surface, and was vaporized by the hot surface temperatures, the water was cycled back into the atmosphere. This water cycle lasted for over 600 million years. From the constant cycling of this slightly acidic water, small pools and ponds began forming on the continental crust. As the runoff from the granitic continental crust eroded away minerals and salts, they were carried into the oceans and seas, where we now have a 3% salt solution in our oceans. |
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