Week 2 Lecture

Question 1

When is the Precambrian?

Answer 1

time before ca. 541 million years ago

Question 2

What are the three eons of the Precambrian?

Answer 2

Hadean
Archean
Proterozoic

Question 3

How is hadean observed?

Answer 3

no rocks only minerals

Question 4

What was the suns luminescence in the Hadean?

Answer 4

The sun’s luminescence was 25-30%
weaker in the Hadean Eon compared
to today.

Question 5

What is the faint sun hypothesis?

Answer 5

Sun was weaker but there was liquid water
Earth must have had a greenhouse effect very early on
A CH4/CO2-rich atmosphere

Question 6

What is the only paleoclimate archive of the Archean?

Answer 6

Sediments from this time are our only paleo-climate

archive

Question 7

What formed the crustal shell and the hydrosphere?

Answer 7

Volcanism on Earth formed a basaltic crustal shell and a water-rich atmosphere and eventually a hydrosphere.

Question 8

When did plate tectonics start?

Answer 8

2.7Ga

Question 9

How did continents affect the ocean?

Answer 9

there was no ocean mixing beforecontinets

ocean currents changed

Question 10

When and where do banded iron formations form?

Answer 10

in water as chemical sediments when water is rich in
soluble Fe, which then becomes unstable
and drops out

Question 11

What is the significance of Banded iron formations?

Answer 11

Banded iron formations indicate the presence of oxygen in the atmosphere(life).

Question 12

What happened to the Earth’s first atmosphere?

Answer 12

it was lost