Cave

Groundwater, like surface water, can change the shape of the land. As water trickles down through the soil can into the rock. Below, it may mix with a gas called carbon dioxide, which is found naturally in the air and the soil. When mixed with the carbon dioxide, water becomes mildly acidic, which makes it possible to dissolve some types of rock. The solution of water, dissolved rock, and carbon dioxide is carried away to streams and gradually flows to the sea, where it may combine with other solutions and form new rock material. If a hole with an opening to the surface is left where the rock dissolved, the hole is called a cave.Caves can be many shapes and sizes. Large caves with connecting chambers are known as caverns. They are cool, dark, and silent places, where the only sound may be the steady dripping of water as it trickles on rock surfaces.This water, which frequently carries dissolved rock material, can form marvelous deposits. The most common of these are stalactites. Like icicles made of stone, stalactites are formed when water rich in dissolved rock material drips from cave ceilings. Stalagmites are another deposit formed by water carrying dissolved rock material. They resemble icicles that grow upward from the cave floor. If a stalactite and a stalagmite join, they create a column.
Sinkholes, another land feature created by groundwater, are large pits formed in much the same way as caves are-acidic groundwater dissolves certain rock material. In fact, some sinkholes form when the roofs of caves collapse. And many sinkholes drain into caves.

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