How has the Earth changed? Flashcards
Includes fossils
What were the 8 previous continents?
Vaalbara
Ur
Kenorland
Columbia
Rodinia
Pannotia
Pangaea
What was Vaalbara?
3.5 Billion years ago.
A single small continent
What was Ur?
3 Billion years ago.
Half the size of Australia
What was Kenorland?
2.7-2.6 Billion years ago.
Supercontinent
What was Columbia?
1.8 Billion years ago.
1/3rd of present land area
What was Rodinia?
1.0-0.6 Billion years ago.
Supercontinent
What was Pannotia?
0.65-0.56 Billion years ago.
Short lived supercontinent
What was Pangaea?
0.3-0.17 Billion years ago.
Last major supercontinent
What did Pangaea break into?
Gondwana and Laurasia
(Iapetus ocean between)
When did Pangaea first break up?
Around 200 million years ago (Triassic)
What did Gondwanaland become?
Antarctica, South America, Africa, Madagascar, Australia and India
When did Gondwanaland break up?
In the Cretaceous
When did Gondwanaland hit Laurasia?
In the Carboniferous.
What is stage 1 of the Wilson cycle?
Breaking of stable continent from thinning + fracturing.
Likely due to a mantle plume.
New divergent boundary
E.g. EARV
What is stage 2 of the Wilson cycle? (after new divergence)
Ocean basin generated ridge push.
E.g. Red Sea
What is stage 3 of the Wilson cycle? (after ridge push starts)
Ocean basins widens.
Ocean is opening while subducted occurs further down.
Growing ocean.
E.g. Atlantic Ocean
What is stage 4 of the Wilson cycle? (after growing ocean)
Closing stage. Subduction.
Convergent boundary.
E.g. Pacific ocean
What is stage 5 of the Wilson cycle? (after subduction)
Most ocean subducted.
Continents close to colliding.
Convergence is still happening
e.g. Mediterranean
What is stage 6 of the Wilson cycle? (after most ocean subducted)?
Collision.
Ophiolite suite in mountain range.
No more tectonism
When did the Great Oxygenation Event occur?
Around 2.8 Billion years ago
What caused the Great Oxidation Event? (drivers)
Cyanobacteria.
These were photosynthetics. Started releasing oxygen for the first time
Why was the introduction of oxygen such a big deal?
It was new.
It was poisonous to the species around (micro-organisms).
What did earliest photosynthetics absorb?
CO2 and CH4
(Carbon dioxide & Methane)
What did the early absorption of CO2 & CH4 do to the climate?
Less greenhouse gases led to colder climates.
Led to a global ice age
What was the name of the ice age caused by the Great Oxidation Event?
Huronian Glaciation
Why were oceans red in during the Great Oxidation Event?
Oxygen reacted with Fe (iron) in the oceans - which covered most of the land.
This formed the BIFs
What is the order of the Geological column?
Cambrian
Ordovician
Silurian
Devonian
Carboniferous
Permian
Triassic
Jurassic
Cretaceous
Paleogene
Neogene
Quarternary
What was the Primitive atmosphere like?
Probably H and He, but these likely escaped (light gases).
Gases from volcanoes. Water vapour, Nitrogen, Ammonia, Methane and Carbon dioxide
How did oceans form from the Primitive atmospheres?
H2O vapour condensed to form the oceans.
Leaving CO2 as the dominant gas
When were oceans first formed?
Around 4 Billion years ago
What are the current CO2 levels in the atmosphere?
Around 430ppm
How have CO2 levels changed over 600 million years, and how do current levels compare?
Overall, the current CO2 levels seem high but are actually low compared to what they have been.
When were the highest CO2 levels measured? (atmosphere)
Cambrian.
Dropped after this from photosynthesis formation.
jumped from 4500-7000ppm for a short period of time.
Once the iron was oxidised in oceans, what did the oxygen do?
Move to the atmosphere
What did the Great Oxidation allow for?
The Cambrian explosion
What is ‘greenhouse Earth’?
Warm periods on Earth.
Lack of ice coverage + overall increase in global temps.
What causes greenhouse Earth?
Can be an increase in solar radiation or a change in atmosphere gases (concentration).
Can be volcanic events
What is meant by Eustacy?
Changes in the volume of the sea resulting in changing sea levels.
E.g. due to temps (expansion) or changes in ocean floor (pillow lavas)
How do rocks evidence climate change?
Different rocks more prevalent in different climates.
Some are only present in certain climates.
Weathering can vary with climate
What does coal tell us about the environment of deposition?
Lots formed in the carboniferous due to warm and wet.
Productive ecosystems (peat).
Rapid plant growth.
High rainfall + temps
E.g. rainforest
What does desert sandstone tell us about the environment of deposition?
Hot, arid, dry.
Sad at surface = red (oxidation).
Fine, rounded, sorted = high energy.
Mostly quartz.
Wind dunes, deserts
What do evaporites tell us about the environment of deposition?
Quick changes from wet-dry.
Low rainfall + high evap.
Deserts
What do tillites tell us about the environment of deposition?
Glacial deposits - cold.
Ancient boulder clay. Commonly high latitudes
What does reef limestone tell us about the environment of deposition?
Warm + shallow.
Mainly built of colonial corals to restricted latitudes (30N+S)
What is paleontology?
The branch concerned with fossilised organisms
How does Paleontology evidence climate change?
Different organisms based on different atmospheric conditions, some are specific climates.
Based on modern day animals and how they relate
What evidence does coral provide for past climates?
