Monday, August 9, 2010

Origin of the Earth

Earth science examines our planet’s structure and the geological processes at work within it and on its surface. It considers rock formation and composition, and the geological evolution of the earth. Land sculpting agents, weather and mapping conclude the study.
Planet earth is a small, dense, rocky planet that is unusual in several aspects. It has free oxygen in its atmosphere; water is present in three phases- ice, liquid and vapor, and surface temperatures are maintained in a relatively narrow range. Life forms play a key role in maintain the balance of conditions on Earth. The interior is layered. Radioactive decay in the interior releases heat and which slowly rises to the surface. Convection currents within the semi solid mantle produce volcanic hot spots. The currents create new ocean crust and push the continents around like floating rafts. About 4700 million years the young sun began to shine, blowing the remaining material of the solar nebular into a ring of dust, gas and ice. Rocky silicates condensed out nearest the sun; gases and ices were driven further.
Gravity and impacts helped the rocky material clump together. Radio activity and the heat of impacts melted the larger proto planets so that iron could sink and form a core; So that the iron could sink and form a core. Depression in the young earth’s surface that became the ocean basins may have been created by impacting comets.  The first atmosphere was composed of gases expelled by volcanoes. A Mars sized object hitting the planet may have produced moon.