Laboratory Manual for Introductory Geology 4e

FIGURE 14.2 Groundwater landscape erosion from beneath the Earth’s surface.
Groundwater dissolves
limestone, forming caves.
(a) Origin of sinkholes by dissolution and collapse.
Caves grow, decreasing support
of ground surface.
Ground collapses, forming
steep-sided sinkholes.
Future karst towers
Water infiltrates along
intersecting fractures.
(b) Origin of karst towers as erosional remnants.
Limestone is dissolved along
fractures.
The general ground surface is lowered by dissolution;
limestone remaining between fractures stands above
surface as karst towers.
(c) Origin of karst valleys along fractures.
form when these cavities grow so large that the ground above them collapses
because there is not enough rock to support it. Karst towers are what remain when
the rock around them has been dissolved (FIG. 14.2b). Karst valleys form when
several sinkholes develop along an elongate fracture (FIG. 14.2c).
Unlike streams and glaciers, groundwater does not produce landforms by deposition.
Groundwater deposition occurs in caverns when drops of water evaporate,
leaving behind a tiny residue of calcite—sometimes on the roof of the cavern, sometimes
on the floor. These deposits build up slowly over time to produce stalactites
and stalagmites, respectively (FIG. 14.3). In some instances, a stalactite and stalagmite
may grow together to form a column.
14.3 LANDSCAPES PRODUCED BY GROUNDWATER
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