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Geology of Landscapes
Chapter 6
(Building Earth’s Surface – Faulting and Folding)
___________
• Process of _________ that _______ the earth’s ________
Stress and Strain
• Any solid material responds to a force in a way that
depends on:
– pressure (force per unit area)
– nature of the material
– other factors
• temperature
______ to _______
•
•
•
•
1. ________
2. _______ deformation (recovery)
3. ________ deformation (no recovery)
4. _______
________
• A _____ that tends to ________, pull apart, or _______ a
rock
– _______ stress
• pushing together or against
– __________ stress
• pulling apart
– ________ stress
• sliding past
________
• The adjustment (______) to stress
– ________ strain
• rocks ________ original shape after stress stops
– _________ strain
• rocks molded or bent do ______ recover
– ______ strain
• rock cracks or _________
Rock Response to Stress
• 1. Nature of the rock
• 2. Temperature
• 3. Pressure
• 4. Speed of stress
Rock Response to Stress
• __________
– _____ rocks
– located on ______
– stress applied ________
– B represents cooler rocks near surface
Rock Response to Stress
• _______ Deformation
• _______ rocks
– ______ _____buried
– stress applied gradually
– A represents deeply buried, warm rocks, under high pressure
Nature of Rock
• Quartz and garnet are brittle
– _________ and __________ fracture
• Mica and calcite are ductile
– _________, schist, limestone and _________ fold
Folding
• _________
– ________ in layered bedrock
Parts of a fold
• __________
– two sides of a fold
• ______ _______
– the imaginary line where two limbs come together
• _______ ________
– an imaginary plane which intersects the crest or trough in such a manner
that the limbs or sides of the fold are symmetrically arranged with reference
to it.
Kinds of Folds
•
•
•
•
•
Anticline
Syncline
Dome
Basin
Monocline
___________
• ______-shaped fold
Syncline
• __________ __________ fold
– limbs dip inward in opposite directions toward fold axis
________
• _________ bulging fold
– __________ or elliptical _____________
– Little Sundance Mountain, WY
– Inward facing cliffs
________
• ________ bulging fold
– ___________ or elliptical shaped ________
– outward facing cliffs
_____________
• No change in dip direction across the fold axis
– layers _______ in the ________ direction
Monocline, Anticline, Syncline
Geosyncline
• A very large syncline
– E.g., San Joaquin Valley
________ Folds
• Anticlines and synclines whose ________ _______ is not
___________
Plunging Folds
• Appalachian Ridges and Valleys
• Pennsylvania
Shapes of Folds (recognize picture)
• open folds
– weak compression
– parallel but opposite forces
Shapes of Folds (recognize picture)
• Isoclinal Fold
– Intense compression
– parallel, but opposite forces
Shapes of Folds (recognize picture)
• Overturned fold
– Not parallel, but opposite forces
– Upper arch overrides lower trough
• Recumbent fold (recognize picture)
– beds between arch and trough horizontal
Folds
Folds in Metamorphic Rock
Anticline or Syncline?
Anticline or Syncline?
Anticline or Syncline?
Anticline or Syncline?
Type of Fold?
Type of Fold?
Evolutionary Belief vs Creationist Belief
Principle of Uniformity vs.
The Great Flood
James ______
•
(1726-1797)
• __________ of __________ Geology
• Scottish Farmer
• Principle of ________
– major tenet of geology
Principle of Uniformity
• The evolutionary belief _________ _________ are caused by
______ _______ over a long time period, many of which are
operating at the present time.
– “The present is the key to the past”
The Story of James Hutton
• Belief in East/West Europe and North America was that
God created the world in about 4000 B.C.
• James Hutton assumed his observations at Siccar Point
meant that the Earth was unimaginably old (KNOW)
– ‘no vestige of a beginning, no prospect of an end’
Siccar Point
Uniformists on Rock Formation
• Hutton based idea of old earth on assumption
– Radiometric dating was developed about 100 years later
• He assumed that the same slow processes eroding the Scottish
highlands in the present formed the ancient rocks by the North Sea
in the past.
Sedimentary Rock Formation
• Uniformists teach that it takes millions of years for
sedimentary rock to form.
•Creationists believe that it can take very little time for
sedimentary rock to form
Rapid Rock formation
• Car keys encased in solid sandstone found on Oregon coast
– Thought to belong to a 1960’s model car
Rapid rock formation
• Australian scientists have developed a revolutionary
new chemical process that transforms loose
sediment into rock within days.
– Mimics natural processes.
• Does not use strange, synthetic materials
Creationists on Rock Formation
• Rocks do not take millions of years to form
• Rocks only need the right conditions
– Floodwaters flowing over the Earth during The Flood dumped
the huge deposits of sediment. And the same floodwaters
contained the dissolved chemicals that quickly cemented the
sediment into rock
Folded Rock
• Uniformists believe that folded rocks were deformed
over millions of years by gradual application of heat
and pressure.
– assume there was no global flood
• Creationists believe that the folding of rocks took
place during the Great Flood some 4400 years ago.
Creationists on Folding
• Rock must have been deformed while the sediment
was still unconsolidated and saturated with water.
– severely deformed rock with hardly any
fracturing
• If the rocks had been hard and solid before they were
deformed, they would have fractured, not folded.
Creationists on Folding
• Minerals and texture of the rock indicates no evidence
that the rocks had been subjected to much heat or
pressure.
– bending had taken place at normal temperatures.
–
Genesis Flood
• Involved rapid movement of plates comprising
earth’s crust.
– the fountains of the great deep broke forth
and the floodgates of the heavens were
opened’ (Genesis 7:11)
• Explains why so much sediment was
still soft when it was deformed.
– No sooner would floodwaters have
deposited great volumes of mud and sand
than moving plates would have crumpled
and deformed the sediment while it was still
saturated.
• The Flood also explains the colossal forces
needed to fold enormous areas of hard rock.
Creationists on Folding
• Just as swirls in a rainbow cake were formed
quickly before the mix was baked into cake,
folds in much of the crust of the Earth were
formed quickly in a great watery catastrophe
before the rocks were solidified
________
• __________ of rocks in response to stress
– Joints
– Faults
_______
• A _______ in a rock along which ____ appreciable _______ has
occurred.
Columnar Jointing
• The Devil’s Tower, Wyoming
________
• A ______ in the earth’s _______ along which _________ has
occurred
Fault Plane
• The surface along which a rock body has broken and been
displaced
Types of faults
• _______________ of _________ ____________
– angle between plane and imaginary horizontal plane
• _____________ of ____________
– dip - up and down
– strike - horizontally or sideways
– oblique - elements of both directions of movement
Hanging Wall and Footwall
Classification of Faults
• _____________ Faults
– ___________ movement
• one side moves up and the other side moves down.
– __________ and ___________
______ Fault
• Hanging wall _______
• Footwall _____
• _______ Stress
• Occurs at _________ plate boundaries
Fault Blocks
• ___________ Faults
• __________
– Dropped-down block
• __________
– Upraised block
_______ Fault
• Hanging wall _____
• Footwall _______
• __________ Stress
• Occurs at ___________ plate boundaries
__________ Fault
• A reverse fault with _________ fault plane
• ____________
– hanging wall block completely ___________ footwall
• sometimes for miles
Strike Slip Fault
• ___________ movement along cracked rock
– example: ________ __________ Fault
• forms due to __________ stress
Strike - Slip Fault
Oblique Fault
• A fault exhibiting __________ a _______ ___________and a
__________ __________
Oblique fault
• Oblique fault produced during 7.7 magnitude earthquake of 1915
• Pleasant Valley, Nevada
What kind of Fault?
What kind of Fault?