Earth Sciences Set 2 Flashcards
What did Alfred Wegener discover?
Wegener was the first to publish the idea that there were plates on the earth’s surface that moved around.
What is continental drift?
Continental drift is the movement of the earth’s plates.
How did Wegener come up with the idea of continental drift?
Wegener noticed that the continents looked like a jigsaw puzzle that could fit together.
What is Pangaea?
Pangaea is the supercontinent, the theorized continent that was the orginal land mass.
How long ago did Pangaea exist?
Pangeae is thought to have existed 225 million years ago.
What does Pangaea mean?
Pan means entire, gaia means earth
Was Pangaea the only supercontinent?
No, scientists think there may have been a supercontinent before Pangaea
Why was Wegener’s theory of continental drift not accepted right away?
People did not believe Wegener because he could not explain the cause of the drifting.
What was Wegener’s profession?
Wegener was a meteorologist, someone who studies weather, so geologists did not believe he knew anything about the earth.
How did Wegener think the continents moved around?
Wegener thought continents moved because of the earth’s rotational pull
How did fossil evidence support Wegener’s theory?
Fossils of similar types of plants and animals have been found on the shores of different continents
Where have Mesosaurus fossils been found.
Messosaurus fossils, a reptile, were found in Africa and Brazil (S. America) along shorelines.
Where was a land reptile called Lystrosaurus found?
Lystrosaurus was found in Africa, India and Antartica in land that is the same age.
What is the Theory of Plate Tectonics?
The Theory of Plate Tectonics is that there are plates moving around, not just continents.
What are tectonic plates?
Tectonic plates are pieces of the lithosphere and crust whcih float on the athenosphere.
On what do tectonic plates float?
Tectonic plates float on the athenosphere.
What are the seven tectonic plates
African plate, Antartic plate, Eurasian plate, Indo-Australian plate, North American plate, Pacific Plate, South American Plate
Are thes seven major plates the only tectonic plates?
No, there are secondary plates and microplates which do not make up significant land mass.
What do tectonic plates move?
Tectonic plates move land masses (continental crust) and ocean (ocean crust)
Do the tectonic plates stop moving?
No, the tectonic plates are continuously moving because they are floating on liquid rock.
Why are plates able to move?
tectonic plates can move because the lithosphere which makes the plates has a higher strength and lower density that the underlying athenosphere.
How fast are tectonic plates moving?
Tectonic plates are moving at about 10-40 mm per year about as fast as fingernails grow
What concept helped geologists accept the Theory of Plate Tectonics?
As they realized about sea floor spreading, they realized the theory was correct.
What is sea floor spreading?
Sea floor spreading iis where ocanic plate are moving away from each other – diverging
How does sea floor spreading happen?
Sea floor spreading happens when cracks appear in the lithospehre which allows magma (liquid rock) to seep through and form new sea floor
When plates are moving towards each other this is called…
convergence is when plates are moving towards each other.
What is obduction?
Obduction is when material pushes upwards forming mountains
What is subduction?
Subduction is when material pushes down into the mantle.. ie when one plate slips underneath another
If the earth floor is spreading and material is pushing up onto the surface, then why is the earth not overflowing with new layers?
The material lost through subduction roughly balances the new formation under the ocean.
What is found where tectonic plates meet?
Where tectonic plates meet, you find earthquakes, volcanoes, mountains and ocean trenches.
What do mountains and volcanoes have in common?
Mountains and volcanoes are both places where tectonic plates meet
Why are all mountains not volcanoes?
There are two types of plates – oceanic and continental. Where ocean plates split and diverge, lava can seep up and form volcanoes
How are mountains formed?
Mountains are formed when two continental plates collide and converge on land, one pushes up against and on top of the other plate
What is the Mid Atlantic Ridge?
The Mid Atlantic Ridge is an undersea mountain range that extends from the Arctic Ocean to the southern tip of Africa.
What can you find in the Mid Atlantic Ridge?
There are lots of volcanoes under the ocean at the Mid Atlantic Ridge as the sea floor is spreading there.
What country is located on the Mid Atlantic Ridge?
Iceland is on the ridge, so it is very volcanic.
What mountain range would have been caused by continental collision?
The Himalayan Mountains were caused by tectonic plates colliding and subduction.
What happens when an oceanic plate bumps into a continental plate?
The oceanic plate will slide underneath (subduction) the continental plate because it is denser.
How do coastal volcanoes like Mt. Saint Helens get made?
When the ocean plate subducted, the plate became hot, melted, turned to magma and then had to find its’ way to the surface. Pressure built up and then exploded in a volcano
