Earths history

Question 1

what is comprised of our solar system?

Answer 1

• our solar system formed about 4.6 billion years ago
• Includes Sun, hundreds of thousands of asteroids and comets, and eight planets
• Earth is third closest planet to the Sun
• Earth’s Moon formed from collision with planet (Theia) about 4.5 billion years ago — residual material coalesced to create Moon

Question 2

Asteroids and Impact Craters

Answer 2

• Earth has been pounded by large asteroids – throughout its history
• Eventually, most objects in Earth’s orbit were swept up by these collisions
• Large objects still hit Earth sometimes and form impact craters

Crust: Earth’s molten surface cooled and hardened into a rigid surface

Question 3

The atmosphere

Answer 3

• Earth’s atmosphere formed from gases emitted by volcanoes

Volcano: a mountain or hill formed by eruptions of lava and rock fragments

• Over 4 billion years ago, water vapor from volcanic emissions condensed out of the atmosphere and collected in low-lying areas of crust, forming oceans

Question 4

life on earth

Answer 4

• Early atmosphere was transformed after cyanobacteria evolved about 3.5 billion years ago

Cyanobacteria: photosynthetic bacteria
- Oxygen concentrations increased during Great Oxidation Event 2.4 billion years ago — ozonosphere formed
- Ozonosphere blocks UV rays — made it possible for life to leave oceans and move onto land

Question 5

Stromatolites:

Answer 5

are colonies of cyanobacteria, and was among the earliest forms of life preserved in the fossil record.

Stromatolites found today in Western Australia
Their fossils date as far back as 3.5 billion years

Question 6

geologic time scale

Answer 6

• Earth’s history divided into epochs, periods, eras, and eons based on major geologic events (e.g., mass extinctions where at least 75% of all species go extinct)
• 4.6 billion yrs old

Question 7

Uniformitarianism:

Answer 7

the principle that the same gradual and nearly imperceptible processes operating now have operated in the past.

“The present is the key to the past.”

Uniformitarianism underpins almost all evolutionary, tectonic, and erosional processes.

Question 8

how to put a date on materials?

Answer 8

Relative age: compares age of one object or event with age of another without specifying how old either is — accounts for order of events.

Absolute age: an age that is specified in years before the present