equinox
a point at which, everywhere on Earth, days and nights are nearly equal in length
solstice
a point at which days are longest in one hemisphere and shortest in the other
portion
part of a whole
weathering
a process that breaks rocks down into tiny pieces
erosion
a process in which water, ice, or wind remove small pieces of rock and move them somewhere else
sustain
to provide something necessary; to maintain
deposition
the process of depositing, or dropping, eroded material
plate tectonics
a process involving huge blocks of Earth's crust and upper mantle
faults
seams in Earth's crust that are often near the boundaries between plates
magma
molten rock