Unit Six - Geological Time - Early Evolution

Question 1

What Happened 4.6 Billion Years ago?

Answer 1

Earth formed

Question 2

What Happened 4.5 Billion Years ago?

Answer 2

Earth heated up due to radioactive decay of isotopes.

Question 3

What Happened 4.4 Billion Years ago?

Answer 3

During early Earth’s melting, material separated into zones according to its densities

1. Iron and Nickel settled into core
2. Silicates formed the earliest crust
3. Gaseous compounds made up the atmosphere

Question 4

What Happened 4.2 Billion Years ago?

Answer 4

1. Solid crust formed
2. Plate tectonics started
3. Outgassing - Gases trapped inside the Earth seeped out creating a completely different atmosphere

Question 5

What Happened 3.9 Billion Years ago?

Answer 5

1. Cooling of the Earth Occured
2. Water vapor in the atmosphere began to precipitate and form liquid water on Earth.

Question 6

What Happened 3.8 Billion Years ago?

Answer 6

Weathering, erosion, and deposition began and the first sedimentary rock formed.

Question 7

What Happened 3.5 Billion Years ago?

Answer 7

1. Life forms that used CO2 and released O2 evolved
2. Oxygen collected in atmostphere

Question 8

What Happened 3.5 - 2.8 Billion Years ago?

Answer 8

1. Oxygen in the atmosphere reacted with iron in the soil
2. Earth Rusted
3. Surface resembled Mars

Question 9

What happened 2.8 Billion Years ago?

Answer 9

1. Most iron compounds already reacted to oxygen
2. Collection of oxygen in the atmosphere increased

Question 10

What happened 2.8 Billion Years ago to Present Day?

Answer 10

Life slowly evolved from singe - celled bacteria to multicellular to hard parts on life forms.