How Was the Earth Formed?

The formation of the Earth--and all the billions of other planets, stars and assorted bodies in the universe--is a story of being in the right place at the right time. Since you can't walk back through history to see what happened, you have to depend on the best guesses of cosmologists and geologists to put together a theory of the beginning. Most theories agree that Earth was formed from cast off material from a star. The Big Bang theory holds that all matter came from one great explosion of matter and another theory holds that the bang came from the end of the collapse of a black hole when the energy absorbed became greater than the gravity of the hole. Another theory contends that the universe is forever expanding then falling in upon itself, repeatedly throwing out stars and planets, then drawing them back in to the center. Every culture has its own mythology concerning the origin of the universe and the formation of the Earth. When you read them all, though, they bear striking similarities to each other and to modern scientific theory.

A little less than five million years ago, a star became super nova and exploded, causing a tidal wave of matter. Some of it started whirling around, smashing together to form bodies of burning hydrogen and helium. A large body, our Sun, had enough mass to exert enough gravity to gather gaseous clouds of matter in orbit around it. Matter in this cloud combined to form smaller bodies which, as they orbited the Sun, smashed into each other, forming larger bodies which became planets, asteroids and other planetisimals and cometisimals. The third larger body circling the sun, protoearth, was a ball of boiling molten rock. As it cooled, though, the denser metals sank toward the center and the lighter metals surfaced and formed a crust. As the planet cooled, gas escaped from the center, throwing up volcanoes on the surface that belched water vapor, carbon dioxide, sulfur, nitrogen, argon and chlorine up. A few planetary collisions later, protoearth had enough water vapor in orbit around it to begin forming an atmosphere. If the atmosphere of Venus and Mars are any indication, Earth had the right planetary mass and was far enough away from the sun to disperse most of the carbon dioxide in its atmosphere but hold on to a hospitable atmosphere composed of 75 percent nitrogen and 25 percent oxygen.

More planetary collisions occurred as Earth rolled on, contributing mass, water vapor and a moon to its progress. When enough water vapor accumulated in the atmosphere, it began to rain, further cooling the surface. Running water formed channels and oceans as the crust split and re-formed giant continents of solid crust floating on the shifting mantle over the molten core. All of the elements were present, whether by cosmic accident or some design, for life to begin developing on the new planet we call Earth.

Resources

• Read this Article in Spanish
• Explanations and activities for kids
• Research on the age of the Earth
• Creationist theory on the formation of the Earth