|Activity 3: Geologic Cross Sections|
|Geologic cross sections are useful
spatial and temporal relationships of geologic units that occur in an area.
maps, we can construct
geologic cross sections (vertical planes of the
show geologic structures
beneath the surface. The top of a cross section shows the topography of the land and below that
relations of the
different rock units that crop out at the surface. Geologic information such as strike and dip is used to project the units that crop out at the
surface into the
subsurface. Cross sections are extremely useful for visualizing the spatial and temporal
relationships of the geologic units that occur in an area. With a little bit of
practice, it is a
fairly straightforward procedure to create a cross section from a map.|
Steep river canyons, sea cliffs, and mountain sides are natural cross sections. Roadcuts are also cross sections. Most cross sections are made by projecting surface features into the Earth or by interpreting data from seismic waves. Cross sections have been used to identify potential petroleum drilling sites, understand the movement along faults, unravel geologic structure in complexly folded regions, determine the flow of water, and plan mining operations.
Steps for making a geologic cross section from a geologic map include (Fig. 1)