Lecture 1: Introduction Flashcards
What is an Eon and how many are there in the history of the Earth?
An Eon is biggest section or chapter of time that exists in dividing up the earth’s history. There are 4
What are the four Eon’s of earth history?
Hadean, Archean, Proterozoic, Phanerozoic
What planets does Earth have a very different atmospheric composition to?
Venus and Mars
What carbon gases are much more common on Venus and Mars?
Carbon Monoxide and Carbon Dioxide
What is a strange characteristic of the earth’s atmosphere which would outside of the earth system be unexplainable?
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
What part of the earth system is responsible for ensuring there is a concentration of both methane and oxygen?
The biosphere (plants) because they provide a constant supply of oxygen through photosynthesis
What % dimmer was the Sun in the early history of the earth?
~70%
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?
There is evidence of LIQUID water on the planet at the time of when the sun was dimmer
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?
Greenhouse Gas Effect
In very brief summary, what is the argument of the Gaia Hypothesis?
Plants control and change the composition of the earth’s atmosphere based on their preferences at the time
When did the Hadean eon stretch from?
4.6-3.8 Ga before present
How is the Hadean Eon characterised?
A volatile volcanic planet, continuously struck by asteroids, very hot
What was the atmospheric composition of the Hadean Eon like?
Lots of carbon dioxide and nitrogen. Very little oxygen
When did the Archean eon stretch from?
3.8-2.5 Ga before present
How is the Archean Eon characterised?
Declining volcanic activity, beginnings of life,
What was the beginning of life like during the Archean?
“Simple life forms” (bacteria) without a nucleus, which were small microbes that precipitate rocks.
How did the emergence of simple life forms in the Archean Eon affect the atmospheric composition?
They produced oxygen and methane whilst promoting the increase of hydrogen. This meant they all saw a relative increase in the atmospheric composition.
What was the Great Oxidation Event?
the largest increase of oxygen in the atmosphere seen in the Earth’s history.
What was the impact of the Great Oxidation event on the earth?
The landscape became oxidised, decline of methane and therefore greenhouse effect which caused snowball earth event
When did the Proterozoic Eon stretch from?
2.5-0.54 Ga before present
What happened ~2Ga in the Proterozoic Eon?
There was the emergence of complex life forms known as eukaryotes
How did eukaryotes differ from simple life forms?
they had more elements such as a nucleus and mitochondria for the cell
What happened ~0.54Ga in the Proterozoic?
The first evidence of ‘animals’ emerges
What happened very shortly after the first evidence of animals? What did this suggest about them?
Two major snowball earth events. This suggested that life was already able to survive intense conditions despite being in its early stages
When did the Phanerozoic Eon stretch between?
0.54 Ga before present to the present day
What event took place between 0.46-0.36 Ga? What did/ did not it consist of?
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
As a result of the plant evolution event, what happened to the atmosphere and what effect did this have and why?
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.
What event took place ~300 Ma and why?
Major glaciation - because of the cooling impact plant evolution had on the atmosphere.
What will eventually happen to the Sun?
It will expand in to a red giant endangering all aspects of the biosphere unless it manages to move to another planet somehow
