Tectonic Plates Flashcards
(18 cards)
why is continental crust less dense than oceanic crust
continental crust contains silica (less dense)
oceanic crust contains basalt (more dense)
where is the ocean crust the oldest
(at divergent boandries)
near the continents
where is the ocean crust the youngest
(at divergent boandries)
near the boundary itself
reversed/normal polarity
indicated by a + for normal and a - for reversed
(Kaila if you know more about this feel free to add it)
is earth’s current polarity normal or reversed?
normal
why do sediments accumulate faster near the continents?
the continents contain more rocks to be weathered away by the environment, forming sediments.
what are the 3 types of tectonic plate boundaries?
divergent, convergent, transform
transform plate boundaries
plates sliding past each other
–>
<–
convergent plate boundaries
plates colliding into one another
–> <–
divergent plate boundaries
plates moving away from one another
<– –>
transform plate boundary description
a few deep earthquakes, mostly shallow
linear valleys or broken stream beds
no volcanoes
convergent (continental-continental) plate boundary description
crust buckles
mountain ranges, shallow earthquakes
convergent (continental-oceanic) plate boundary description
oceanic crust subducts
volcanic mountain chain, deep and shallow earthquakes, trenches, tsunamis
convergent (oceanic-oceanic) plate boundary description
older crust subducts
volcanic island chain, trenches, tsunamis, earthquakes
divergent plate boundary description
new ocean crust formed, mid-ocean ridge, rift valley, oozing volcanoes, fracture zones, shallow earthquakes
What were some of Alfred Wegener’s reasons for continental drift
- coastlines of South America and Africa match up
- common fosils
- rock formations
- mountain ranges
- minerals
what were some objections to the continental drift theory?
lacked mechanisms for movement
What makes tectonic plates move?
convection in the asthenosphere
