21 - Earth & Atmospheric Science Flashcards
What components formed the Earth’s early atmosphere?
- large amount of Co2
- Little to no oxygen
- Water vapour
- Small amounts of other gases (e.g. Nitrogen, Methane, Ammonia)
What formed Earth’s early atmosphere?
Intense volcanic activity
How did the condensation of water vapour form the oceans?
Around 4 billion years ago, the Earth cooled down to cause water vapour in the atmosphere to condense to liquid water
Explain how the amount of Co2 in the atmosphere was decreased
Co2 dissolved in the water and carbonates were precipitated producing sediments
—> Reducing the amount of CO2 in the atmosphere
How did the amount of oxygen increase in the early atmosphere?
Algae & plants produced the O2 that is now in the atmosphere by photosynthesis
—> They decreased the amount of Co2 in the atmosphere
What is the chemical test for oxygen?
Uses a glowing splint inserted into a test tube of the gas
—> Splint relights in oxygen
Describe the greenhouse effect
Some of the energy transferred to the Earth is absorbed, warming it up
Warm Earth emits infrared waves.
Some gases in the air absorb energy transferred by the infrared waves.
When the gases re-emit the energy some of it goes back to the Earth’s surface & warms it
What are greenhouse gases?
The gases in the atmosphere that absorb energy
Give some examples of greenhouse gases
- Methane
- Water vapour
- Carbon dioxide
What would the earth’s temp be like if we didn’t have greenhouse gases?
Mean temp of Earth would be -18 degrees
What is a casual link?
One thing causes another
How do we show there is a casual link?
Scientists must collect evidence & explain how and why the correlation occurs
How do we measure the historic amount of Co2 levels?
By measuring concentrations of the gas trapped in ice cores
Why is methane a more powerful greenhouse gas than Co2?
It’s much better at absorbing infrared radiation from the Earth
How is methane produced & released?
- Livestock farming - bacteria in cow’s stomachs produce methane
- Released when oil & natural gas are extracted from the ground & processed
What are some effects of climate change?
- Rising sea levels - High temps cause ice to melt
- Animals may become extinct - If they cannot survive at warmer temps or find new places to live
- More extreme weather events - will change wildlife & growth of crops
- Organisms in the seas/ oceans will be harmed - More Co2 will dissolve in seawater, lowering its pH
- Coral bleaching
How does coral bleaching occur?
As ocean temps rise. it causes coral to push out the photosynthetic algae that live in their tissues
—> These algae provide the colour of coral & so coral ‘bleaching’ may occur
How can we reduce greenhouse gas emissions?
- Using renewable energy resources
- Global engineering solutions
What are the risks of using global engineering solutions?
That some countries will not help & that delicate ecosystems may be disrupted
What are the risks of helping local people adapt to new conditions?
May destroy important habitats & there is a risk they will not work
What is the problem of using renewable energy resources?
This may not be enough to mitigate the effects of climate change we are seeing
What is the evidence used to show that there was little to no o2 in the early atmosphere?
Iron Pyrite found in ancient rock. The compound is broken down by oxygen & so only forms if there is no oxygen
What evidence do we have to show oxygen started to increase 2.4 billion years ago?
Rocks containing bands of iron oxide started to form
—> Oxidation of iron suggests that o2 levels increased @ this time
Who began to increase o2 levels 2.4 billion years ago?
Fossil evidence of microorganisms producing this o2
—> Microorganisms reacted with iron in early oceans to produce insoluble iron oxides that formed layers on the sea bed
What gas do scientists think made up Earth’s early atmosphere?
Co2
What supports the idea that earth’s early atmosphere contained a lot of Co2?
Earth, Venus & Mars are rocky planets w/ volcanos.
Venus & Mars’ atmospheres are mainly made of Co2 - thought to have been released by volcanos
What percentage of our modern day atmosphere is made up of O2?
21%
What percentage of our modern day atmosphere is made up of Nitrogen?
78%
Give an example of one of the earliest photosynthetic organisms?
Cyanobacteria - live in shallow waters
Explain why cyanobacteria need to move above the sediment as it collects in layers on a stromatolite
They move above the sediment in order to get sunlight to photosynthesis
Give some characteristics of cyanobacteria
- Grow in huge colonies
- Produce sticky mucus which traps a layer or sand grains & other sediments
