The Atmosphere Flashcards
Name the gases that make up today’s atmosphere - and there percentages
Nitrogen - around 78%
Oxygen - Around 21%
There are also small proportions of other gases (e.g. carbon dioxide, water vapour and noble gases such as argon)
For how long have the gases in the atmosphere stayed pretty constant
For 200 million years, the proportions of different gases in the atmosphere have been much the same as they are today
Why can’t scientists be certain about the Earth’s early atmosphere
The Earth is around 4.6 billion years old, therefore scientists cannot be certain about the Earth’s early atmosphere
Explain how the early atmosphere changed into the atmosphere now - Volcanoes
During the first billion years, there was intense volcanic activity. These volcanoes releases the gases that formed the atmosphere. One of these gases was water vapour.
As the earth cooled, the water vapour condensed to form the oceans.
Volcanoes also released huge amounts of carbon dioxide. In this early stage, the Earth’s atmosphere consisted mainly of carbon dioxide with little or no oxygen
Volcanoes also released other gases. These include nitrogen which gradually built up in the atmosphere.
Volcanoes also released small amounts of methane and ammonia.
What can the Earth’s early atmosphere be compared to
The Earth’s atmosphere then was very much like the atmospheres of Mark and Venus today
State the gases which formed the earth’s early atmosphere
The early atmosphere mainly consisted of carbon dioxide with small but increasing amounts of nitrogen
Carbon dioxide
Water vapour
Nitrogen
Ammonia and Methane
State the differences between the early atmosphere and today’s atmosphere
The early atmosphere contained large amounts of carbon dioxide but the atmosphere today only contains a small amount
The early atmosphere contained a small amounts of nitrogen but the atmosphere today contained large amounts
The early atmosphere contained very little oxygen whereas today 21% of the atmosphere is oxygen
Explain how carbon dioxide was removed from the atmosphere
The water vapour from volcanoes condensed to form the oceans.
At this stage, some of the carbon dioxide dissolved in the oceans to form a weak acid. This reacted with mineral in the sea to form precipitates
Over time, this formed sediments of carbonate rock on the sea bed.
Some of the carbon dioxide in the sea was used to make corals and shells of organisms such as mussels
When these died, they formed the sedimentary rock, limestone. This also removed carbon dioxide from the atmosphere
Algae and plants decreased the percentage of carbon dioxide in the
atmosphere by photosynthesis.
Carbon dioxide was also decreased by the formation of sedimentary rocks and fossil fuels that contain carbon.
Photosynthesis happening in algae and plants takes in carbon dioxide and produces oxygen.
The carbon can then be trapped in fossil fuels and again that caused the level of carbon dioxide in the atmosphere to fall.
Explain how oxygen got into the atmosphere
Around 2.7 billion years ago, photosynthetic algae first evolved in the oceans.
Photosynthesis produced oxygen which entered the atmosphere.
Over the following billion years, plants evolved. This increased the amount of oxygen in the atmosphere.
At some point, the level of oxygen reached the point where animal could evolve.
State the different fossil fuels
Coal
Oil
Gas
Describe how fossil fuels are formed
For how long are fossil fuels formed over
Fossil fuels are formed over millions of years
Fossil fuels are
a. renewable
b. non-renewable
Fossil fuels are non-renewable
How is coal formed
Coal is formed from the remains of ferns and trees.
If these die in marshy wetlands then they do not decompose. That can be due to lack of oxygen or acidic conditions. These both prevent bacteria from carrying out decomposition.
Over time, the plant remains are covered with sediment and are compressed. High temperature and pressure creates coal.
How is oil formed
Crude oil is formed from plankton which are tiny plants and animals found in the sea. When these die, they settle in mud on the sea-bed.
If oxygen is not present, then they do not decompose.
Over time, they are compressed by sediment.
Heat and pressure then coverts them into crude oil
