| 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 |
| magma chamber | where magma is stored under a volcano |
| volcano | an opening in Earth's crust through which molten rock, rock fragments, and hot gases erupt |
| shield volcano | usually largest type of volcano; gentle sloping sides; non-violent fluid lava flows |
| cinder cone volcano | small and simple type of volcano; usually has only one vent; short violent eruptions |
| crater | hollowed out bowl-shaped area at the top of a volcano |
| lava | name for magma when it reaches earth's surface |
| composite volcano | stratovolcano; eruptions for layers; often violent eruptions; most common type; tall and steep sided |
| earthquake | the shaking of the ground caused by the sudden movement of large blocks of rock along a fault |
| epicenter | the point on earth's surface directly above the focus of an earthquake |
| focus | the point underground where tectonic plates first begin to move during an earthquake |
| secondary waves | seismic waves that cannot travel through core (liquids); slower than primary waves |
| surface waves | slowest moving seismic waves; can cause ground to roll like ocean waves; damage structures on earth's surface |
| magnitude | measurement of an earthquakes strength based on seismic waves and movement along faults |
| primary waves | fastest seismic waves; first released during an earthquake; travel through all layers of earth |
| tsunami | giant wave caused by an underwater earthquake |
