Acidic groundwater slowly dissolves limestone beneath the surface, creating empty spaces. When the roof of that hollow space can no longer support the ground above, it collapses and forms a sinkhole.

Gravity constantly pulls everything downward. On steep slopes, loose rocks and soil cannot resist this pull, so they slide, tumble, or fall downhill in events like landslides and rockfalls.

When a fast mountain stream reaches flat ground, it suddenly slows down and spreads out, dropping its sediment in a fan or triangle shape. This landform is called an alluvial fan.

Water carrying dissolved minerals drips inside a cave and slowly evaporates. As the water disappears, it leaves behind tiny layers of minerals that build up into stalactites hanging from the ceiling and stalagmites rising from the floor.

Water expands about 9% when it freezes into ice. If water is trapped inside a crack, the expanding ice pushes against both sides of the crack, widening it -- a process called frost wedging.

Rows of trees block the wind before it reaches open farmland. By slowing the wind, the trees prevent it from picking up and blowing away valuable topsoil.

Carbon dioxide from the air dissolves in rainwater to form carbonic acid, a weak acid. This acid reacts with minerals in rock, slowly dissolving them in a chemical weathering process called carbonation.

Waves erode the weaker parts of a cliff first, leaving behind a tall, isolated column of harder rock standing in the water. This leftover pillar is called a sea stack.

Rocks frozen into the bottom of a moving glacier scrape across the bedrock like nails on a chalkboard. The long, parallel scratches they leave behind are called glacial striations and are evidence that a glacier once passed through.

Each feature is built by deposition in a different setting: rivers flood and build floodplains, mountain streams spread sediment into alluvial fans, ocean currents pile sand into barrier islands, and dripping mineral water creates stalactites in caves.