C1.7 Flashcards
Where do earthquakes and volcanoes tend to occur and why?
Plate boundaries, because of the movement of plates against each other, sliding and colliding
What causes the movement of the tectonic plates?
Because of convection currents in the mantle, driven by heat released by radioactive processes happening in the core
Where did oxygen come from in the early atmosphere?
Oxygen was a waste product produced by plants and algae through photosynthesising
How can we get liquid nitrogen from air?
Fractional distillation of air - cooling the air a lot, and then allowing it to gradually warm up so the fractions separate. Liquid nitrogen is mainly used for cooling things, such as biological specimens
What are tectonic plates?
They are pieces of the earths outer shell that glide over the mantle and move at about 2cm per year
What is a plate boundary?
Where two plates meet
What was Albert Wegener’s theory?
It was that the earth’s continents were once joined. It was named the theory of Continental Drift and was proposed at the beginning of the 20th century. His evidence was that the continents fit together like a puzzle and there are similar fossils and rocks on the edges of the continents
What is Pangea?
It was the supercontinent that existed 250 million years ago, before continental drift began to happen
Why do we not know how life was first formed?
Because scientists are unable to know for sure what caused life and how it first began because they don’t have evidence
What are the percentages of the gases in today’s atmosphere?
78% Nitrogen
21% Oxygen
1% Other noble gases, mainly argon
0.03% Carbon dioxide
What was responsible for the formation of the earth’s early atmosphere and provided the water that formed the oceans?
Intense volcanic activity because it released mainly carbon dioxide, as well as water vapour which condensed to form the oceans
What happened to a lot of the carbon dioxide that had been in the air?
The percentage of it decreased because of photosynthesis, and because it got locked into sedimentary rocks such as limestone and was dissolved into oceans
What human activities have caused a change in our atmosphere?
The burning of fuels such as carbon has increased the level of carbon dioxide in the atmosphere, as well as rising the rate of global warming and temperature
What was Miller-Urey’s experiment?
The experiment tested whether our origin of life had evolved through chemical reactions involving amino acids. They used the gases present in the early atmosphere, water to represent the sea, sparks to simulate lightening, a condensed to cool the atmosphere, and heat.
What are three other theories for the beginning of life on Earth? (not Miller-Urey or Wegener)
Other theories include:
Panspermia - that life exists elsewhere and started through meteorites, asteroids etc.
Spontaneous Generation - that life derives from different forms (eg A bee from a plant)
Materialistic Theory - that life comes from chemical evolution, about 3.8 billion years ago
What is limestone made from?
Limestone is made from sedimentary rocks and contains mainly calcium carbonate
