Cavern and Mineral Deposits: How Caverns Form

1. Cavern and Mineral Deposits:How Caverns Form • Limestone dissolves more easily than other types of rock • Limestone is dissolved by groundwater because it always contains some carbonic acid. • Dissolving the calcite in limestone creates/increases porosity • Limestone formations are also split by fissures • After 1000's of years, cracks become so large that they form networks of underground tunnels • These tunnels are caverns, or caves

2. Sinkholes form when parts of a cave roof collapses. • Ponds or lakes form when the sinkhole meets the water table

3. Karst Topography • In regions of caverns, most rainwater enters the ground through sinkholes and fissures, and there are very few surface rivers • Regions characterized by sinks, sinkhole ponds, lost rivers, and underground drainage are said to have Karst Topography • The bedrock is calcite, dolomite, or other minerals that dissolve easily • Video link

4. Mineral Deposits by Groundwater • Minerals dissolved in groundwater are deposited in a variety of ways • When water drips from the roof of a limestone cave is deposits calcite as stalactites • On the floor beneath the stalactites, blunt, round masses called stalagmites are formed. • Columns or pillars form when they meet • These are examples of dripstones, and only form when water can evaporate above the water table.

5. Calcite deposits around mineral springs are called travertine • Hot water pours out of long hillside fissures, depositing some calcite as it cools. • Geyserite forms around the opening of geysers, it is silica dissolved from the hot igneous rock through which the geyser water pass. • Petrified wood is formed when minerals dissolved in groundwater replace the decaying wood of buried trees • The most important groundwater deposit is the cement that binds together sand grains and pebbles of sedimentary rocks.