COMPOSITION AND STRUCTURE

FORM: The shape of the Earth is very similar to that of an oblate spheroid, a sphere flattened at the poles, resulting in a bulge around the ecuador.Este bulge is caused by the rotation of the Earth, and causes the diameter at the Ecuador is 43 km longer than the diameter of one pole to another. Approximately 22 000 years ago the Earth had a more spherical shape, most of the northern hemisphere was covered by ice, and as the ice melted causing less pressure on the earth's surface that is causing this type held "rebound", this phenomenon continued to occur until the mid-nineties when scientists realized that this process was reversed, ie, the swelling increased, satellite observations GRACE show that at least since 2002, the ice loss from Greenland and Antarctica has been primarily responsible for this trend. The average diameter of the reference spheroid is about 12,742 km, which is approximately 40,000 km / π, as the meter was originally defined as one ten-millionth of the distance from Ecuador to the North Pole from Paris, France.

CHEMICAL COMPOSITION: The mass of the Earth is approximately 5.98 × 1024 kg. (32.1%), oxygen (30.1%), silicon (15.1%), magnesium (13.9%), sulfur (2.9%), nickel (1.8% It is composed mainly of iron ), calcium (1.5%) and aluminum (1.4%), with the remaining 1.2% consisting of small amounts of other elements. Because mass segregation, it is believed that the core region is mainly composed of iron (88.8%), with small amounts of nickel (5.8%), sulfur (4.5%), and less than 1 % consists of trace elements.


INTERNAL STRUCTURE: The interior of the Earth, like that of the other terrestrial planets, is divided into layers by their chemical composition or physical properties (rheological) properties, but unlike the other terrestrial planets, it has a different inner and outer core. Its outer layer is a solid crust silicate, chemically distinct, under which there is a high viscosity solid mantle. The crust is separated from the mantle discontinuity Mohorovičić, varying the thickness of the same from an average of 6 km in the oceans between 30 and 50 km on the continents. The crust and the upper cold and rigid upper mantle are commonly known as the lithosphere, and it is of the lithosphere that the tectonic plates are comprised. Below the lithosphere is the asthenosphere, a layer of relatively low viscosity of the lithosphere floats. Within the mantle, between 410 and 660 km below the surface, significant changes in the crystal structure. These changes create a transition zone that separates the upper and lower part of the mantle. Under the mantle is a liquid outer core of extremely low viscosity, resting on a solid inner core. The inner core may rotate at an angular velocity slightly greater than the rest of the world, moving from 0.1 to 0.5 ° per year.