Lecture 1: Introduction

Question 1

What is an Eon and how many are there in the history of the Earth?

Answer 1

An Eon is biggest section or chapter of time that exists in dividing up the earth’s history. There are 4

Question 2

What are the four Eon’s of earth history?

Answer 2

Hadean, Archean, Proterozoic, Phanerozoic

Question 3

What planets does Earth have a very different atmospheric composition to?

Answer 3

Venus and Mars

Question 4

What carbon gases are much more common on Venus and Mars?

Answer 4

Carbon Monoxide and Carbon Dioxide

Question 5

What is a strange characteristic of the earth’s atmosphere which would outside of the earth system be unexplainable?

Answer 5

There is the concentration of both methane and oxygen in the atmosphere which are highly reactive to each other and so would otherwise have disappeared as single elements from the atmosphere by now

Question 6

What part of the earth system is responsible for ensuring there is a concentration of both methane and oxygen?

Answer 6

The biosphere (plants) because they provide a constant supply of oxygen through photosynthesis

Question 7

What % dimmer was the Sun in the early history of the earth?

Answer 7

~70%

Question 8

What is there evidence of existing in the earth’s early history which shows that despite the sun being a lot dimmer it was not too cold and frozen over?

Answer 8

There is evidence of LIQUID water on the planet at the time of when the sun was dimmer

Question 9

What effect, which is very strong on the earth, was responsible for counteracting/balancing out the reduced solar insolation the sun was providing to the earth when it was 70% dimmer?

Answer 9

Greenhouse Gas Effect

Question 10

In very brief summary, what is the argument of the Gaia Hypothesis?

Answer 10

Plants control and change the composition of the earth’s atmosphere based on their preferences at the time

Question 11

When did the Hadean eon stretch from?

Answer 11

4.6-3.8 Ga before present

Question 12

How is the Hadean Eon characterised?

Answer 12

A volatile volcanic planet, continuously struck by asteroids, very hot

Question 13

What was the atmospheric composition of the Hadean Eon like?

Answer 13

Lots of carbon dioxide and nitrogen. Very little oxygen

Question 14

When did the Archean eon stretch from?

Answer 14

3.8-2.5 Ga before present

Question 15

How is the Archean Eon characterised?

Answer 15

Declining volcanic activity, beginnings of life,

Question 16

What was the beginning of life like during the Archean?

Answer 16

“Simple life forms” (bacteria) without a nucleus, which were small microbes that precipitate rocks.

Question 17

How did the emergence of simple life forms in the Archean Eon affect the atmospheric composition?

Answer 17

They produced oxygen and methane whilst promoting the increase of hydrogen. This meant they all saw a relative increase in the atmospheric composition.

Question 18

What was the Great Oxidation Event?

Answer 18

the largest increase of oxygen in the atmosphere seen in the Earth’s history.

Question 19

What was the impact of the Great Oxidation event on the earth?

Answer 19

The landscape became oxidised, decline of methane and therefore greenhouse effect which caused snowball earth event

Question 20

When did the Proterozoic Eon stretch from?

Answer 20

2.5-0.54 Ga before present

Question 21

What happened ~2Ga in the Proterozoic Eon?

Answer 21

There was the emergence of complex life forms known as eukaryotes

Question 22

How did eukaryotes differ from simple life forms?

Answer 22

they had more elements such as a nucleus and mitochondria for the cell

Question 23

What happened ~0.54Ga in the Proterozoic?

Answer 23

The first evidence of ‘animals’ emerges

Question 24

What happened very shortly after the first evidence of animals? What did this suggest about them?

Answer 24

Two major snowball earth events. This suggested that life was already able to survive intense conditions despite being in its early stages

Question 25

When did the Phanerozoic Eon stretch between?

Answer 25

0.54 Ga before present to the present day

Question 26

What event took place between 0.46-0.36 Ga? What did/ did not it consist of?

Answer 26

The evolution of plants on the land. It was only small plants such as fungi and small insects. Tall trees and forests did not emerge till later

Question 27

As a result of the plant evolution event, what happened to the atmosphere and what effect did this have and why?

Answer 27

Plant evolution meant that photosynthesis increased which used up CO2 which then reduced the greenhouse gas effect and temperature of the earth. It also led to an increase in the concentration of oxygen.

Question 28

What event took place ~300 Ma and why?

Answer 28

Major glaciation - because of the cooling impact plant evolution had on the atmosphere.

Question 29

What will eventually happen to the Sun?

Answer 29

It will expand in to a red giant endangering all aspects of the biosphere unless it manages to move to another planet somehow