Chapter 9

pangea

all the continents were once part of a super continent

continental drift

continents are in the constant motion on the surface

mid ocean ridges

mountain ranges in the middle of the oceans

seafloor spreading

the process by which new oceanic crust forms along a mid ocean ridge and older oceanic crust moves away from the ridge

normal polarity

a state in which magnetized objects such as compass needles, will orient themselves to point north.

magnetic reversal

magnetic field reverses direction.

reversed polarity

a state in which magnetized objects would reverse direction and orient themselves to point south.

plate tectonics

states that earths surface is made of rigid slabs of rock or plates that move with respect to each other.

lithosphere

the cold and rigid outermost rock layer

divergent plate boundary

where two plates separate

transform plate boundary

where two plates slide past eachother

convergent plate boundaries

where two plates collide

subduction

the denser plate sinks below the more buoyant plate

convection

the circulation of material caused by differences in temperature and density

ridge push

rising mantle material at mid ocean ridges creates the potential for plates to move away from the ridge with a force

slab pull

as a slab sinks it pulls on the rest of the plate with this force