C1.1 The Earth's sea and atmosphere Flashcards
What is an atmosphere?
The layer of gas surrounding a planet
What do volcanoes on Earth release?
- carbon dioxide
- water
- ammonia
- methane
- nitrogen
Why do scientists believe that there was little or no oxygen in the early atmosphere of Earth?
- volcanoes don’t release oxygen
- iron compounds found in the Earth’s oldest rocks would only form in the absence of oxygen
How do scientists think oceans formed?
They think that the Earth got colder as it got older, so water vapour in the hot atmosphere condensed to form oceans
How was carbon dioxide in the early atmosphere reduced?
- it dissolved into the oceans
- some marine orgamisms used dissolved carbon dioxide to make their shells
- the production of limestone
What type of rock is limestone?
Sedimentary
What compound is limestone made from?
Calcium carbonate
How is limestone produced?
- marine organisms die
- their shells and skeletons fall and become sediment
- layers of sediment build up over millions of years and become limestone
When do scientists believe life started on Earth?
4 billion years ago
When do scientists believe some organisms developed the ability to photosynthesise?
1 billion years ago
How did the amount of oxygen in the Earth’s early atmosphere gradually increase?
More photosynthesising organisms evolved which meant that the rate at which carbon dioxide was removed and oxygen was added increased
What percentage of dry air is nitrogen?
78%
What percentage of dry air is oxygen?
21%
What percentage of dry air is argon?
0.9%
What percentage of dry air is carbon dioxide?
0.04%
