Geological Work of Ground Water

Geological work of ground water is important in solution and deposition in the rocks through which it passes. It dissolves limestone and other carbonate rocks to form caves and sink holes. Limestone areas are often marked by a karst topography of sinks, few surface streams (they flow underground), and large springs. In caves, the deposition of calcite dissolved in dripping groundwater produces stalactites, icicle-shaped formations hanging from the cave ceilings, and stalagmites, formations that build up from the cave floor. The carrying away of minerals in solution usually occurs above the water table. Below that level, deposition, replacement, and cementation are important. Ball-like masses (concretions), hollow, globular bodies (geodes), and the cement in many sedimentary rocks are the result of the action of ground-water at depth.

Exercise 7. Read the text “Geological work of ground water” and fill in the following diagram:

…(from the ceiling)

…

…

…

sinks

… topography

sink holes

…

…

other carbonate rocks

Above

solution

…

Geological work …

Water table

Below

…

…

cementation

	…			cement in many sedimentary rocks

the result …