Volcanoes
Why does magma flow upward through rocks?
It has low density.
Earthquakes occur at the ___________, while the point on the surface directly above is called the _______.
focus, epicenter
What type of plate boundary describes when the plates are pulled apart?
Divergent
What landform is created at a transform boundary?
Faults, earthquakes
New crust forms at...
What type of volcanoes have low viscosity?
Shield
What type of boundary would you expect to experience the most earthquakes? (hint.. San Andreas)
Transform
convection currents.
A rift valley forms at what type of plate boundary?
C-C Divergent
What causes seafloor spreading?
Magma rising from the asthenosphere at divergent boundaries OR convection currents.
Iceland formed over a.....
hotspot
Most earthquakes and volcanoes happen....
at plate boundaries
In a normal fault, the hanging wall moves, ____ and it has ________ stress.
down, tension.
Which type of plate boundary creates a mid-ocean ridge?
O-O Divergent
Who came up with the theory of seafloor spreading, but couldn't prove its true?
Alfred Wegener
How do cinder-cone volcanoes form?
Piles of rock and ash that build up.
________ is a measure of the amount of energy released during an earthquake.
Magnitude
In a reverse fault, the hanging wall move ______, and it has _________ stress.
up, compression
Which type of plate boundary creates a deep ocean trench?
O-C, Convergent
Who discovered the Mid-Atlantic Ridge, proving seafloor spreading?
Marie Tharp
As volcanoes erupt on land, the cooling lava becomes...
Continental crust
Moment Magnitude Scale
Who used SONAR to map the ocean floor and find evidence for plate tectonics?
Harry Hess
Japan is an example of a volcanic island arc created by what type of plate boundary?
O-O Convergent
Name two types of evidence scientists have for seafloor spreading.
magnetic reversal, rock age, fossil age.