Transcript Mountains, Folds, and Faults Notes

Mountains, Folds, & Faults
What happens to the Earth’s crust
when forces are applied to it.
Objective #1 - Forces
(Copy this table.)
Direction
Name of
Force
Cause
 
• Tension - a pulling, stretching force.
• Caused by the divergent part of
convection where magma comes up
and then spreads to the sides.
or
• Caused by elastic rebound.
• (1789)
 
• Compression - a squishing force.
• Caused by plate collisions.
• (1788)

• Buoyancy or Isostacy - a lifting force.
• Caused by density differences in a
fluid.

• Gravity - a force pulling downward.
• Nobody knows what causes gravity. ( We do know
that both mass and distance influence the amount
of force - Thanks Newton :)
• If you figured out what causes gravity, you would
win the Nobel Prize in Physics!
Objective #2 Styles of Deformation
• How the Earth’s crust responds to
stress.
Elastic Deformation
• When a force is applied the crust becomes
deformed.

• When the force is
released - the crust
returns to its original
shape (but possibly
offset).

Plastic Deformation
• When a force is applied - the crust
becomes deformed.
• When the force is released - the
crust stays deformed.
Brittle Deformation
• When a force is applied - the crust
breaks!
• (1788-9)
Objective #3
(Copy this table.)
Temperature • High
• Plastic
• Low
• Brittle
Duration = how long
• Long time
• Plastic
• Short period
• Elastic
Moisture Present
• Wet
• Plastic
• Dry
• Brittle
Amount of Force
• A lot
• Brittle
• A little
• Plastic or Elastic
Speed Force is Applied
• Fast
• Brittle
• Slow
• Elastic or Plastic
Age of Crust
• Old
• Brittle
• Young
• Elastic or Plastic
Depth
• Deep
• With depth comes
heat and moisture.
• Plastic
• Remember that many
geologic features you
see at the surface
formed way
underground.
• Shallow
• Shallow will be dry
and cool.
• Elastic or Brittle
(Others)
• (High)
• (Low)
(Other Considerations)
• The type of material combined with the
type of force make a big difference!
• Bridges
Isostacy
• Means standing the same.
• Saucer dispenser at café
•
Crust thickness
Objective #4 Structures
Anticline = an Upfold
• Force = compression
• Style = plastic
• (17917,1834,1937,1826)
Syncline = a Downfold
• Force = Compression
• Style = Plastic
• (1854, 1860, 1862, 1867, 1869, 1938, 1839)
Faults
Normal Fault
• Force = Tension
• Style = Brittle
• The side on top of the slope (headwall)
naturally slides down the slope (footwall).
(26938, 1802, 1817, 1908, 1899, 1900, 1925)
Reverse Fault
• Force = Compression
• Style = Brittle
• The side on top of the slope (headwall) is
pushed up the slope (footwall).
• (27119, 1803, 1901, 1903,1816, 1895)
•
•
•
•
Transform Fault
Force = Compression or Tension
Style = brittle
Two pieces move side-by-side.
(27300, 1804, 1911)
Dome Mountains
•
•
•
•
Force = Buoyancy
Style = Plastic
Rising magma bends overlying rock layers upward.
(1798, 1861)
Folded Mountains
• Force = Compression
• Style = Plastic
• Compression folds layers into synclines and
anticlines. The surface becomes ridges and
valleys. (3559)
Fault Block Mountains
•
•
•
•
Force = Tension or Compression
Style = Brittle
Blocks move up or down along parallel faults.
(1812, 3558)
Volcanic Mountains
• Formed by eruption of lava that piles
up to form a mountain.
How to prepare for the TEST:
• The drawing below shows a piece of the
Earth’s crust before force was applied.
• Draw an after structure that would result
from each of the following cases.
• A) Compression with plastic deformation
• B) Tension with brittle deformation
• C) Compression with brittle deformation
TEST preparation cont’d.
• If the drawing below shows the upper
surface of the Earth’s crust, draw
the bottom of the crust.
TEST preparation cont’d.
• We went over all of your objectives.
• Study your notes and practice each
objective.
• Don’t forget to make flash cards for
EXTRA CREDIT!!!