AQA GCSE Core Science C1 Part B: The Earth's atmosphere

The atmosphere today:

78% Nitrogen
21% Oxygen
0.9% Argon
0.037% Carbon Dioxide
+ traces of other gases such as water vapour.

The early atmosphere of Earth:

Scientists believe that the Earth was formed 4.5 billion years ago (the big bang theory). The Earth's early atmosphere consisted of mainly carbon dioxide and methane - quite like Venus and Mars' atmosphere today! 

The Earth's consists of:

The crust (solid)
The mantle (has properties of a solid but flows very slowly)
Outer Core
Inner Core

Both the inner core and the outer core are made from liquid nickel and iron. The radius of the core is just over half way the radius of the Earth.

Continental drift:

Albert Wegener came up with this idea that the continents were once joined together (at the time of pangaea) but have gradually split apart over time.

THERE IS EVIDENCE TO SUPPORT THIS - IT IS NOW CONSIDERED A THEORY.

There are two types of tectonic plates:

- Oceanic plates. These occur under the oceans.

- Continental plates. These are from the land.

NB: Oceanic plates are denser to continental plates.

Convection currents in the mantle cause tectonic plates to move.

It is difficult to predict when an earthquake or volcano will happen or how big it will be, even in places known to have earthquakes and active volcanoes occur.

Increasing oxygen:

- through photosynthesis

Decreasing carbon dioxide:

- dissolving in the oceans

- the production of sedimentary rocks such as limestone

- the production of fossil fuels from dead plants and animals.

Burning fossils fuels is adding more carbon dioxide to the atmosphere faster than it can be removed.

MORE CO2 = MORE GLOBAL WARMING

The primordial soup theory states that billions of years ago, the Earth's atmosphere was rich in nitrogen, hydrogen, ammonia & methane.

- Lightning struck, causin a chemical reaction between the gases, producing amino acids.
- The amino acids gradually combined to produce organic matter, which eventually evolved into living organisms.

The Miller-Urey experiment was to see if substances now made by living things could be formed in the conditions thought to have existed on the early Earth.

The two scientists sealed a mixture of water (which was heated to get water vapour), ammonia, methane & hydrogen in a sterile flask.

Electric sparks were passed through thhe mixture of water vapour and gases. After a week, amino acids, the building blocks for proteins, were found.

THE MILLER-UREY EXPERIMENT SUPPORTS THE PRIMORDIAL SOUP THEORY.