The dozen or so plates that cover the surface of the earth and are constantly moving
A sedimentary rock made from the remains of sea animals, which makes up karst terrain
An underground space which is hollowed out by water and which may collapse if the uppermost layer gets too thin
Anything in the environment that humans use
A river that takes a twisting, turning path, like a snake
A mineralized growth that forms starting at the floor of a cave
Wind blowing sand from one location to another
A mineralized growth that forms starting from the ceiling of a cave
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Glaciers dropping rock and sand to form terminal moraines
Caves being formed by acid rain dissolving underground limestone
A long, deep, narrow outlet of the sea located between mountain valleys
A mudslide flowing down a steep hill
A sand hill or ridge formed by the wind; usually in desert regions or near lakes or oceans
Rubbing action (rock against rock or sand against rock) that weathers rock like sandpaper
Depositing eroded rock and soil in other places
A natural source of flowing water, larger than a stream
A natural tunnel within an area of solidified lav, through which molten lava once traveled
Waves dropping sand on the beach
An area of porous limestone where caves and sinkholes are more likely to form
The till deposited at the edges of a glacier that forms a ridge
The thick mass of tough roots at the surface of the soil; keeps soil in place
A flat area of deposited sediment at the place where a river slows and empties into another body of water
The flat area bordering a river, composed of sediment deposited during flooding
The force that moves rocks and other material downhill
