Unit 2 - Plate Tectonics Flashcards
What observation did early mapmakers make when looking at the continents that made them wonder if they might once have been connected?
looked like puzzle peices
Which scientist proposed that all the continents were once connected together?
alfred wegner
What did he call his hypothesis?
continental drift
Was his hypothesis immediately accepted? Why or why not?
no people needed explanation
What did he name his “supercontinent”?
Pangea means all earth
How long ago did he think the supercontinent began to break up?
200 million years ago
Wegner noticed that several features on adjacent continents matched. Which kinds of features matched? (name at least three)
1) rock formation
2) fossils
3) glacier deposits
Before sonar, what did people think the bottom of the ocean looked like?
totally flat
What were we able to see with the help of SEABEAM?
mountain canyons
The deepest canyon on earth is the ___________________________, and the longest continuous mountain range in the world is the _____________________________.
Mariana trench
mid atlantic
Scientists have now identified ________ major tectonic plates that they believe are moving slowly over the earth’s surface.
7
These plates seem to move over a semi-solid/semi-liquid layer just beneath the lithosphere. What is this layer called?
antheosphere
What kind of forces within the earth seem to be pushing and
pulling on plates, causing them to move?
convention currents
What is convection?
transfer of thermal energy by the movement of heated material from one place to another
What is the nickname for the area bordering the Pacific Ocean where plates are colliding?
ring of fire
How did this area get this name?
from all volcanoes and earthquakes around that area
In what direction do plates move at a divergent boundary?
Name an example of a divergent boundary
moving apart
Atlantic ridge or great rift valley on Africa
In what direction do plates move at a convergent boundary?
Name an example of a convergent boundary.
toward each other
mt st Helens mt Everest
If an oceanic plate pushes under a continental plate, what kind of features often form on the continental plate?
volcano
How do plates move at a transform boundary?
Give an example of a transform boundary.
slide past each other
San Andres fault California
When an oceanic plate and a continental plate collide, which one is always pushed underneath?
Why is this plate pushed under, rather than over?
What term do geologists use to mean “pushed under”?
the oceanic plate is more dense than continental plate
subducted
As the plates at the Mid-Atlantic Ridge move apart
magma fills the space that is created. Where are the
oldest rocks on the seafloor found – close to the ridge
or farther away?
farther away
How is earth’s magnetic field “captured” in rocks that are
formed along the MidAtlantic Ridge?
the lava solidifies. iron in it points toward the poles
As scientists have studied the rocks along the Ridge, what have they learned about the Earth’s magnetic field?
it has reversed over time
