| A | B |
|---|
| troposphere | lowest region of the Earth's atmosphere; where weather happens |
| crust | Earth's outermost layer |
| seafloor spreading | Earth's interior is being forced up and pushing the ocean floor apart |
| plate tectonics | crustal movement |
| planetary differentiation | iron and other dense elements sink to the core; less dense material was forced upward toward the crust |
| core | innermost layer of the Earth made of nickel and iron |
| mantle | layer of Earth that surrounds the core |
| seismic waves | vibrations produced by earthquakes |
| convection | warmer material rises; cooler material sinks |
| dynamo theory | convection of iron in the outer core + Earth's rotation creates electric currents which created Earth's magnetic field |
| magnetosphere | Earth's magnetic field |
| solar wind | erratic flow of charged particles away from the Sun |
| Van Allen radiation belts | invisible magnetic field rings around the Earth |
| aurorae | gases in atmosphere fluoresce when solar wind particles leak through our magnetosphere at the poles |
| ejecta blanket | light-colored pulverized rock on the moon from meteorite impacts |
| maria | lava lowlands on the moon |
| mare | one lava lowland on the moon |
| rille | cracks in the lava on the moon |
| highlands | light-colored mountainous areas on the moon |
| regolith | "blanket of stone"; layer of moondust |
| anorthosite | light-colored rock of moon's highlands, rich in calcium and aluminum |
| impact breccia | composites of different rock fused together as a result of meteorite impacts |
| collision-ejection theory | Earth was struck by a Mars-sized object; splashed debris from Earth into orbit; some formed to make Moon |
| synchronous rotation | the same side of the Moon always faces the Earth as it revolves around the Earth |
| tidal forces | differences in the gravitational pull |
