B.P. #4 Materials move within each sphere and between
spheres
Plate tectonic cycle
Plate tectonics 1.
What is plate tectonics?
Concept that features of the earth and earth phenomena
(earthquakes, volcanoes) are caused by motion of plates of
rigid lithosphere moving on a plastic asthenosphere
Important words: crust, mantle, (core), lithosphere, asthenosphere
Which continent has no plate boundaries? Predict its elevation,
presence of mountain ranges?
Controls on action and features at boundaries =
1. Forces
Tension
compression
shear
2. Types of crust = oceanic (dense), continental (undense)
B.P. #4 Materials move within each sphere and between
spheres
Plate tectonic cycle
B.P. #2 The earth is density stratified, with most dense
materials in center, least dense materials on outside
2. Both plates with continental crust
B.
Passive continental margin - Fig. 12-8
mid ocean ridges
1. One plate with ocean crust, one with continental crust
2. Both plates with ocean crust
3. Both plates with continental crust
1. One plate with ocean crust, one with continental crust
Why does ocean crust go under continental crust?
Why does an ocean trench form?
What causes melting of lithosphere (rock) to form volcanoes?
2. Both plates with ocean crust
3. Both plates with continental crust
Why do folded mountains form? Why does crust not get sucked down?
What will happen to the mountains over time?
Where are shields and covered shields? – What part of plates do they occur in?
Where are some folded mountains that are low? – What do they record?
How fast do plates move?
What has been the position of plates in the past?
How will the position of plates change in the
future?
B.P. #5 Present state of earth is temporary - different
in past, future
https://www.youtube.com/watch?v=2It3ETk2MGA
Questions about plate tectonics….
Why is all of the ocean crust so relatively young? Why are the oldest rocks on continents?
Which are the world’s youngest mountains? Relation between age and height?
What tectonic events do the Appalachians record? How high were they at one time?
Where do earthquakes occur with respect to plate boundaries? Any inconsistencies?
Where should folks with severe earthquake-phobia live? What continent?
Where do volcanoes occur with respect to plate boundaries?
What kind of plate boundary is most dangerous to live near?
Why is plate tectonics important?
Controls life support systems – hydrosphere, atmosphere
Controls sea level
How plate tectonics controls sea level and climate
1. Sea level is controlled on a large scale by rate of plate tectonic motion
Compare the height and the volume of the
Mid Ocean Ridge when spreading is fast vs
slow.
Will sea level be high when plates
are moving fast or slowly?
How plate tectonics controls sea level and climate
1. Sea level is controlled on a large scale by rate of plate tectonic motion
Will sea level be high when plates
are moving fast or slowly?
Fast – because mid ocean ridge is
bloated because it has grown so big
while it is still very hot - makes a big
hump on the ocean floor so ocean water
spills over onto the continents
When sea floor spreading is slow, ridge
cools and contracts before it is very wide
How wide is the area of shallow water? Rate?
The East Pacific Rise is spreading very fast… New crust
travels far before it cools and sinks. This makes a very big
bulge on the ocean floor.
Mid Atlantic ridge -
How wide?
Rate?