Changes in the Earth and its atmosphere Flashcards
What are the basic constituents of the Earth?
Core (extremely thick, molten/liquid), mantle (thick, but thinner than the core; semi-solid/liquid in parts) and crust (relatively very thin, solid)
What are tectonic plates?
Where the crust and the upper part of the mantle crack into large pieces, which are the plates
What causes the tectonic plates to move? How fast do they move?
Convection currents within the mantle, with the heat driving them from radioactive processes that occur naturally.
By a few centimetres each year (very slowly)
What can happen when tectonic plates move?
Earthquakes and/or volcanic eruptions occur at the boundaries
The effects can be sudden and disastrous
What are the constituents of the Earth’s atmosphere today (and since 200 million years ago)
About 80% nitrogen, N2
About 20% oxygen, O2
Small amounts of other gases including carbon dioxide, water vapour and noble gases such as argon
What events formed the Earth’s early atmosphere during its first billion years?
Intense volcanic activity released the atmospheric gases as well as water vapour, which later condensed to form oceans
What is one theory about how the atmosphere was formed? (Realise that there are several possible theories, nobody has yet proved any)
In the Earth’s first billion years, the atmosphere was mainly CO2, with little or no O2 gas, as well as water vapour and some methane and ammonia
What is one theory about how life was formed? (Realise that there are several possible theories, nobody has yet proved any)
The primordial soup theory: hydrocarbons (such as methane), water vapour and ammonia might have interacted with the presence of lightning, forming amino acids, the building blocks of life.
What is the Miller-Urey experiment?
An experiment that combined water vapour, ammonia, methane and hydrogen with electrical currents (simulating lightning) that formed amino acids, the building blocks of life
Why is there now (lots of) oxygen in the atmosphere?
Plants and algae photosynthesised, which took CO2 from the atmosphere and produced oxygen from it
Where did much of the carbon in the carbon dioxide in the air end up?
Locked in sedimentary rocks as carbonates and fossil fuels. It dissolved in oceans, and limestone, a carbonate was formed from shells and skeletons of sea creatures
What is air? How can it be split into different raw materials to be used in various industrial processes?
A mixture of gases with different boiling points
Fractional distillation
Why can we not know for sure how life was first formed on Earth?
The first organisms would have been soft-bodied, so we don’t have any fossils of them to study as they would have decayed
We don’t have any evidence of past atmospheric compositions
Any evidence would be found at the bottom of oceans
