Changes in the Earth and its Atmosphere Flashcards
How did scientists use to believe features like mountains and canyons were formed?
That they were formed as the Earth shrunk as it cooled after its creation.
Nowadays, what is generally accepted to be the reason mountains and canyons are formed?
The movement of tectonic plates.
Who first came up with the idea of tectonic plates?
Alfred Wegener
What did Wegener conjecture?
300 million years ago all the continents fitted together into a supercontinent and have since drifted apart.
What were two pieces of evidence to support Wegener’s theory of continental drift?
1) Very similar fossils were found on opposite sides of the Atlantic.
2) Wegener noticed that the continents roughly fitted together.
What were two reasons people resisted Wegener’s theory?
1) Wegener couldn’t prove how the plates were moving. His idea of it being tides and radiation was proven impossible.
2) It was popularly believed that animals crossed continents on land bridges which had since disappeared.
In what decade did Wegener’s theory become accepted by the scientific community?
The 1960s
Give five reasons why the public oftentimes ignore earthquake warnings from scientists.
- Scientists only know when an eruption is likely.
- It is impossible to know the timing of an earthquake.
- There’s no way to accurately predict the strength of an earthquake.
- It’s hard to know where the earthquake will be.
- There’s no way of stopping an earthquake and people don’t like evacuating.
How do scientists try to predict eruptions?
By monitoring mini-earthquakes caused by lava breaking through cracks in the crust. These can often cause false alarm though.
What proportion of the Earth’s atmosphere is Nitrogen?
About 80%
What proportion of the Earth’s atmosphere is oxygen?
About 20%
Describe the early atmosphere.
The Earth’s surface was originally molten and any atmosphere just boiled away. Eventually the world started to cool down and the crust began to form. Volcanoes continued to erupt for another billion years. As such, it is probable that the atmosphere was nearly completely carbon dioxide with some water vapour, methane and ammonia.
How were the oceans formed?
The water vapour in the early atmosphere condensed and fell to the Earth’s surface.
What happened to the carbon dioxide in the atmosphere?
- Some was absorbed by the water.
- Some was taken in by plants and algae for photosynthesis. When they died their stored carbon was locked away in rocks and fossil fuels.
What two problems are caused by releasing carbon dioxide back into the atmosphere?
- Global warming.
* The oceans becoming more acidic.
