Water Erosion: How do processes involving water change Earth’s surface? Part 3 1

What results from water in the atmosphere mixing with CO 2 (carbon dioxide) ? Acid Rain 2

Precipitation and Groundwater Water in the atmosphere combines with carbon dioxide (CO 2 ) to form a weak acid known as carbonic acid. Another term for this is “acid rain”. When the precipitation falls on Earth’s surface, the water that does not evaporate back into the atmosphere or runoff the surface can sink into the ground. Water that soaks into the ground is known as groundwater, and becomes part of the groundwater system. 3

Groundwater Weathering Groundwater weathers rocks which contains CaCO 4 (calcium carbonate). Examples of this type of rock are limestone, marble, and chalk). The groundwater (weak carbonic acid) dissolves those rocks in the process of chemical weathering. 4

Groundwater Erosion As the rock dissolves, it goes into solution with the groundwater, and flows along with the groundwater. This underground movement of chemically weathered rock is known as groundwater erosion. This process will gradually hollow out pockets in the rock. Over time, the pockets develop into large holes called caves or caverns. 5

Cave Formations: How do they form? 6

Groundwater Deposition Once the cave or cavern is established: the groundwater solution can drip from the ceiling to the floor. Evaporation occurs as the solution slowly drips from the ceiling. Evaporation also occurs when the solution has fallen to the floor. As the water evaporates: the minerals (such as calcite) in the solution will be left behind (or deposited) hardening on the ceiling and floor of the cave or cavern causing cave formations. 7

Cave Formations: What are the features found in a cave? 8

Cave Formations What are stalactites? Calcite deposits that hang from the cave’s roof like icicles What are stalagmites? Cone-shaped calcite deposits that build up from the cave floor 9

Ellison’s Cave in Walker County, Geo rgia 10

Karst Topography: What happens when land rich in limestone is weathered and eroded by groundwater? 11

Sinkholes Sinkholes are: depressions in the ground. Sinkholes are caused when : the roof of a cave or cavern collapses because of the erosion of the underlying rock (limestone) with the result being the depression. Sinkhole Formation Animation 12

Karst Topography A Karst Topography is A type of landscape Karst Topography is created in regions where : a layer of limestone near the surface forms deep valleys, caves, caverns, and sinkholes. 13

Karst Topography 14

Karst Topography 15