Lab 10 Geologic Structures

What is Structural Geology?

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The study of how
geologic units were orientated underground when they formed, and after they
were deformed.

Stress vs. Strain:

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Stress is a force
per unit area…it is the force you apply to something.

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Strain is the
resulting deformation that you observe.

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Strain is a
function of how much stress you apply.

ex- You take a lump of clay and pull on it from either
side.  The clay will stretch out the
more you pull it.  In this example,
the stress was the force you exerted on the clay to pull it out sideways, and
the resulting strain was the increase in the clays length.

Geologic Maps:

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Graphical
representation of what geologic units are doing underground.

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Can be used to
understand what is going on deep below the earth’s surface.

Geologic Cross Section:

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A profile view of
an imaginary cut through the earth constructed from a geologic map.

Block Diagram:

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An idealized
schematic drawing of a 3D block that is representative of the geologic
structures observed in your map.

How to describe the Attitude (orientation) of Geologic
Units:

Strike and Dip:

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Strike is the
line created when you imagine a plane intersecting your strata (see below).

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Dip is the angle measurement your bed is dipping from
horizontal.

Hint- use the right hand
rule to determine correct measurement of strike and dip…imagine your
hand on the flat surface of the outcrop pictured above.  If you point your fingers in the
direction of dip (right) then your thumb points in the direction of strike.

*Know the Symbols on page 171*

Unconformities:

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Disconformity =  between
parallel sed units.

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Angular
Unconformity = between dipping and horizontal

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Nonconformity =
between sedimentary and non- sed

Remember the three types of Faulting?

Folds:

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Imagine taking a
group of sedimentary rocks and bending them…this is a fold.

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Anticline is when the fold is concave downward and the oldest
rocks are in the center.

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Syncline is when the fold is concave upward and the oldest
rocks are on the outside (limbs)

*Review and know what basins, domes and monoclines are
also*

Axial Plane: