Deep Time Earth Quiz - lectures 1-6

Question 1

What are the abbreviations for billions and millions of years ago?

Answer 1

Billions - Ga

Millions - Ma

Question 2

The first 3 eras of the Precambrian and the major eon that follows i.e. the 4 major eons into which geologists divide Earth’s history into?

Answer 2

Hadean 4.6-3.8 Ga
Archean 3.8-2.5 Ga
Proterozoic 2.5-0.54 Ga
Phanerozoic 0.54-0 Ga

Question 3

How old is the universe? How old is the Earth?

Answer 3

13. 7 Ga

4. 6 Ga (4.56)

Question 4

Which two elements were made as the universe cooled after the big bang? What process has made the other elements? What is the heaviest?

Answer 4

Hydrogen (H) and Helium (He)

The process of nuclear fusion in stars; stops at iron (Fe) as this is the heaviest and stars run out of fuel eventually

Question 5

How are even heavier elements than Fe made?

Answer 5

Larger stars explode into supernovas and through neutron capture, become neutron stars

Question 6

What is the process of rocky planet formation called? What heated the earliest Earth?

Answer 6

Accretion

Kinetic energy from accretion converted to hear followed by radioactive decay

Question 7

What elements form most of the Earth’s core and mantle? How were they differentiated?

Answer 7

Core = Fe
Mantle = Si
Iron and Silicon are immiscible; Fe is denser so remained in core

Question 8

How was the moon formed?

Answer 8

Collision with ‘Theia’; a planetary embryo about size of Mars

Question 9

Where did the oceans and atmosphere come from? Name two abundant gases in early atmosphere

Answer 9

Volatiles vapourized by immense heat and LHB etc. Degassing from the mantle resulted in atmosphere and some water from carbonaceous chondrite meteorites
N2 and CO2

Question 10

How old is the oldest zircon grain, and how old are the oldest rocks still with us at the Earth’s surface?

Answer 10

Zircon grain = 4.4 Ga

Oldest rocks = 4.28 or 4.04 Ga (differences in accepted evidence)

Question 11

When was the ‘Late Heavy Bombardment’ and when did life originate?

Answer 11

LHB = 4.1-3.8 Ga
Life = 3.8 Ga is earliest proposed evidence

Question 12

How old are the oldest sedimentary rocks and how old are the oldest fossils of life? What is a stromatolite?

Answer 12

Sedimentary rock = 3.8 Ga
Fossils = 3.5 or 3.26 Ga depending on evidence accepted
Stromatolite = fossilised layered carbonate rock structure, made by microbial communities

Question 13

Who came up with the theory of continental drift?

Answer 13

Alfred Wegener

Question 14

Evidence for sea floor spreading (x2) and subduction of ocean plates?

Answer 14

Paleaomagnetism: symmetric magnetic reversals either side of mid-ocean ridge AND thickening sediment layers with distance from ridge
Seismic activity provides evidence of plate boundaries

Question 15

Hold old is oldest ocean floor and roughly how fast do continental plates move apart/together?

Answer 15

150 Ma

10cm/yr (100mm/yr)

Question 16

What is the process of splitting called and what is created upon collisions?

Answer 16

Rifting

Mountain ranges

Question 17

Name of ancient bits of continental crust, a surface location above a mantle plume, and landform above continental crust plume?

Answer 17

1. Cratons/shields
2. Hawaii (Mauno Loa)
3. Flood basalts, or Large Igneous Province

Question 18

Co-existing dis-equlibrium gases? What dominates Mars and Venus’ atmospheres?

Answer 18

Oxygen and Methane OR oxygen and hydrogen

CO2

Question 19

Gaia hypothesis: what is regulated by life? Who created it?

Answer 19

Atmospheric composition and climate

By Jim Lovelock and Lynn Margulis

Question 20

What are some key criticisms of the Gaia Hypothesis and how did Lovelock respond?

Answer 20

Biologists - implies teleology and forethought, not a unit of selection, not natural selection for a wider purpose
‘Daisyworld’ model = biological alterations to environment and climate automatically

Question 21

What is the habitable zone?

Answer 21

Range of distances from a star on which water on a planet is liquid (0-70 degrees temp range)

Question 22

What is the faint young sun puzzle? Role of luminosity, temperature, cycles etc.

Answer 22

Sun was 30% less luminous when Earth formed.
High CO2 levels and perhaps lower albedo kept Earth warm
Silicate weathering was the long-term process that removed CO2 from the atmosphere which counteract steady brightening of the Sun (warming accelerates silicate weathering and removes CO2)