| A | B |
|---|
| inner core | most dense layer of earth; extreme pressure; solid iron and nickel |
| outer core | liquid layer of earth; iron and nickel; responsible for earth's magnetic field |
| continental crust | thickest layer of crust; mostly granite |
| oceanic crust | thinnest, more dense layer of crust; mostly basalt |
| mantle | thickest layer of earth; molten rock material |
| convection currents | movement occurring in asthenosphere; causes tectonic plates to move |
| density | reason structure of earth is in layers |
| lithosphere | all of crust and uppermost part of mantle; broken into tectonic plates |
| plate boundaries | where two plates meet; most earthquakes and volcanoes occur here |
| divergent boundary | where two plates separate away from each other |
| convergent boundary | where two plates collide |
| oceanic-oceanic | type of convergent boundary where deep ocean trenches and island arcs form |
| continental-continental | type of convergent boundary where mountains form |
| transform boundary | where two plates slide past each other; earthquakes commonly occur here |
| subduction | process where one tectonic plate sinks beneath another tectonic plate and into the mantle |
| sea-floor spreading | process when two plates diverge and new ocean crust is created as magma from the mantle rises and spreads out |
| mid-ocean ridge and rift valley | two geographic features that form when plates separate |
| ocean trench | a deep depression in the ocean floor at a subduction zone |
