Post by Admin on Jul 20, 2021 19:53:22 GMT -7
Phase 1 - Accretion and Early Differentiation of the Earth and Terrestrial Planets
The geological process by which the Earth came to have its present interior structure is called differentiation, and is illustrated in the following figure.
The process of geological differentiation
The Solar System and Earth formed about 4.5 billion years ago. Within the first billion years the Earth was melted by heat arising from a combination of sources:
1. Gravitational energy left from the formation of the planet,
2. Energy from Comet, Asteroid, and Meteor bombardment,
3. Decay of radioactive material trapped in the body of the Earth.
While the Earth was molten, gravity acted to concentrate more dense material near the center and less dense material nearer the surface. When the Earth solidified again (except for the liquid outer core) it was left with a layered structure with more dense material like iron and nickel near the center and less dense rocks nearer the surface. As the outer layers cooled and solidified, large cracks developed because of thermal stress, leaving the lithosphere broken up into large blocks or plates.
Also in that first billion years, another planet struck Earth, knocking off much of the crust of both planets. Most of the material was soon drawn together to form the moon.
This had enormous implications for the subsequent geological history of the Earth because it produced conditions favorable for plate tectonics.
agupubs.onlinelibrary.wiley.com/doi/book/10.1002/9781118860359
pages.uoregon.edu/drt/Classes/201_99/Rice/differentiation.html
The geological process by which the Earth came to have its present interior structure is called differentiation, and is illustrated in the following figure.
The process of geological differentiation
The Solar System and Earth formed about 4.5 billion years ago. Within the first billion years the Earth was melted by heat arising from a combination of sources:
1. Gravitational energy left from the formation of the planet,
2. Energy from Comet, Asteroid, and Meteor bombardment,
3. Decay of radioactive material trapped in the body of the Earth.
While the Earth was molten, gravity acted to concentrate more dense material near the center and less dense material nearer the surface. When the Earth solidified again (except for the liquid outer core) it was left with a layered structure with more dense material like iron and nickel near the center and less dense rocks nearer the surface. As the outer layers cooled and solidified, large cracks developed because of thermal stress, leaving the lithosphere broken up into large blocks or plates.
Also in that first billion years, another planet struck Earth, knocking off much of the crust of both planets. Most of the material was soon drawn together to form the moon.
This had enormous implications for the subsequent geological history of the Earth because it produced conditions favorable for plate tectonics.
agupubs.onlinelibrary.wiley.com/doi/book/10.1002/9781118860359
pages.uoregon.edu/drt/Classes/201_99/Rice/differentiation.html