Download Crustal Deformation

Crustal Deformation
Economic Consequences of
Geologic Structures
• Tracing Coal Seams, Aquifers, etc.
• Ore Deposits are often localized along
faults and folds
• Petroleum Traps
Anticlines
and
Synclines
Monoclines
and
Homoclines
Axial Plane
How Fast Can Folds Form?
Which Way was Up?
Sedimentary Structures are governed by:
• Gravity
• Exposure to the Surface
They all have a “right way up”
Foliation
Foliation is a
sheetlike
structure
that forms
when rocks
are
deformed.
Foliation
a. Flattening
b. Grain
Rotation
c. Solution
d. New
Minerals
e. Partial
Melting
f. Shearing
Foliation
In every case, the
foliation is:
• In the direction
of least
resistance
• at right angles
to the direction
of greatest
compression.
Folds and Foliation
• On a small scale (microscopic to
centimeters), foliation forms by a variety of
mechanisms, but always at right angles to
the direction of greatest compression
• On a large scale (centimeters to kilometers),
rocks fold. The axial plane of the fold is
also at right angles to the direction of
greatest compression
Folds and Foliation
The Importance of Minor Folds
How Geologists Use These Clues
• Here's an outcrop that might be seen in the
field.
How Geologists Use These Clues
• Picture the axial
plane of the fold
as parallel to the
foliation.
• The other side
of the fold is
roughly a mirror
image of the
side we can see.
How Geologists Use These Clues
• We can mentally
fill out the sketch
to get an idea of
the shape of the
fold.
• Note that we still
have no idea how
big the fold is,
only what kind it
is.
What if we did
it the other
way?
Isostasy
The Airy Model
The Pratt Model
Both Ideas are Correct at Times
How Isostasy Works
Isostatic
Rebound in
Canada
Isostatic
Rebound in
Scandinavia
Domes and Basins
Domes and Basins
Domes and Basins