Lecture 10: Page 5

Page 5, Review of our Solar System [Previous Page] [Next Page] [Class Home Page] Text Pages 123-124

Comparative Planetology

Our Early Earth
Earth recycles it's surface. Evidence from it's early history is mostly erased. The Moon's surface (left) tells us much about the conditions of the early Solar System, which has been erased on Earth. Curiously, Venus shows few craters (right), like Earth. What does this say about Venus's geology?

Volcanism around the Solar System
Venus (left) and Earth (right) both show geological evidence for volcanism, as demonstrated in the pictures here. However, the lava flows formed on Venus do not extend very far from their source. Such comparison's help us to understand volcanism on Earth and Venus.

Water flows on Mars
There is no water on Mars now, but satellite images of Mars (left) shows features nearly identical to those seen on Earth (right) which are currently caused by water. Is this sufficient evidence to support past water on Mars?

The Developmental Stages of the Forming Earth

Differentiation Material in the Earth separated according to its density, giving Earth a highly dense core. Some may have occurred during formation (inhomogeneous formation), some may have come about from radioactive heating.

Cratering Even after the outer crust had cooled and solidified, the Earth was still bombarded by very large debris, creating enormous craters. Both the size and frequency of these impacts decreased over the first half billion years.

Flooding Heat from radioactive decay in the Earth's interior and enormous impacts forced lava up through fissures in the crust, flooding low lying regions. This also released gases (CO₂, H₂O, etc) locked in the rocks, to create a thick atmosphere. Once the temperature of the surface and atmosphere cooled, the water was able to condense and pool on the surface.

Slow Surface Evolution The effects of volcanism, moving geologic plates, and weathering via water and air, have served to change and evolve the features of the Earth over the last 4 billion years.