Cenozoic
- Created by: sikemi__
- Created on: 13-05-21 16:06
View mindmap
- Climate change during the Cenozoic
- What is the Cenozoic?
- Means 'new life'
- Resetting of the biological clock following mass extinction at the end of the Cretaceous and the beginning of the Palaeocene
- We are still in it - began around 66 million years ago
- Role of foraminifera
- Forams - single celled organisms that secrete calcium carbonate shells
- Found in abundance in upper ocean and in sediment at depth
- Oxygen isotope ratios of shells depend on temperature and oxygen isotope ratio of sea water at time of calcification
- Signal can survive for 100s of millions of years as fossils
- Can be used to find estimates of past ocean temperature (evaporation from ocean surface favours oxygen 16)
- Signal can survive for 100s of millions of years as fossils
- What they showed...
- Global mean temperatures are around 14.5 degrees C now but were around 25 degrees C at the start
- Temps peaked around 50 million years ago but Earth cooled steadily until around 34 million years ago
- Temperature was more or less stable until around 15 million years ago when cooling resumed
- Pace accelerated around 5 million years ago
- Overall cooling trend of over 10 degrees C
- Forams - single celled organisms that secrete calcium carbonate shells
- Geological carbon cycle
- CO2 abundance in the atmosphere can control Earth's climate via greenhouse effect
- Changes in fluxes of sources and sinks are critical
- Primary source of CO2 on geological timescales = volcanic gassing
- Controlled by global rates of sea floor spreading and subduction
- Key sink = chemical weathering of silicate rocks
- An imbalance between sinks and sources leads to feedbacks
- One hypothesis for Cenozoic cooling is that global sea floor spreading rates fell over the past 60 million years
- This would decreasing the CO2 flux from the Earth's interior, depleting the atmosphereof it
- However, sea floor spreading rates increased, so this doesn't explain
- This would decreasing the CO2 flux from the Earth's interior, depleting the atmosphereof it
- CO2 abundance in the atmosphere can control Earth's climate via greenhouse effect
- Reasons behind cooling
- Several mountain ranges were establishedduring this time e.g. Rocky's, Himalayas, Alps
- This led to increased global weathering rates due to exposure of fresh rock and glaciation
- This then led to CO2 drawdown from the atmosphere, so cooler climates (as CO2 is a GHG that absorbs energy and re-emits, some back to Earth
- This led to increased global weathering rates due to exposure of fresh rock and glaciation
- Several mountain ranges were establishedduring this time e.g. Rocky's, Himalayas, Alps
- What is the Cenozoic?
Comments
No comments have yet been made