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Kobe, Japan
FOLDS, FAULTS & MOUNTAIN BELTS
TYPES OF FAULTS
DIP-SLIP FAULTS
Exhibit vertical movement.
Fault blocks move up or down relative to each other.
FOLDS, FAULTS & MOUNTAIN BELTS
TYPES OF FAULTS
DIP-SLIP FAULTS
FOLDS, FAULTS & MOUNTAIN BELTS
TYPES OF FAULTS
NORMAL DIP-SLIP FAULTS
In a NORMAL DIP-SLIP FAULT the hanging wall
moves down relative to the foot wall.
Produced by tensional stresses.
Found at divergent plate boundaries.
Mid-oceanic divergence zone is >60,000 km long.
FOLDS, FAULTS & MOUNTAIN BELTS
TYPES OF FAULTS
NORMAL DIP-SLIP FAULTS
Can produce steps in the landscape.
Steps are called FAULT SCARPS.
FOLDS, FAULTS & MOUNTAIN BELTS
TYPES OF FAULTS
NORMAL DIP-SLIP FAULTS
Tension can produce sequences of normal faults.
Results in production of HORSTS and GRABENS.
Such is the East African Rift Valley and Connecticut
River Valley.
FOLDS, FAULTS & MOUNTAIN BELTS
TYPES OF FAULTS
HORSTS AND GRABENS
FOLDS, FAULTS & MOUNTAIN BELTS
TYPES OF FAULTS
REVERSE DIP-SLIP FAULTS
Hanging wall moves up relative to the foot wall.
Produced by compressional forces.
Found at convergence zones.
Carries older rocks up over younger rocks.
FOLDS, FAULTS & MOUNTAIN BELTS
TYPES OF FAULTS
REVERSE DIP-SLIP FAULTS
A low-angle reverse fault (<45) is called a
THRUST FAULT.
A very low angle reverse fault (<10) is called an
OVERTHRUST.
Large slabs of rock can move horizontally over large
distances.
FOLDS, FAULTS & MOUNTAIN BELTS
TYPES OF FAULTS
REVERSE DIP-SLIP FAULTS
OVERTHRUST FAULT.
Going to the Sun Mtn.
Glacier National Park, MT
FOLDS, FAULTS & MOUNTAIN BELTS
BUILDING MOUNTAINS
MOUNTAIN
Part of the Earth’s crust that stands > 300 m (1000’)
above the surrounding landscape.
Has a discernable top or summit.
Possesses sloping sides.
FOLDS, FAULTS & MOUNTAIN BELTS
BUILDING MOUNTAINS
Every continent has mountains.
Every ocean basin has mountains.
FOLDS, FAULTS & MOUNTAIN BELTS
BUILDING MOUNTAINS
Some mountains are isolated peaks.
Some mountains occur in ranges or systems.
FOLDS, FAULTS & MOUNTAIN BELTS
BUILDING MOUNTAINS
Form in a variety of ways
Catskill Mtns., NY
Eroded Peaks
Mauna Loa, HI
Basaltic Outflowing
Alps
Sedimentation and
Continental Collision
FOLDS, FAULTS & MOUNTAIN BELTS
BUILDING MOUNTAINS
Mountains are being continuously created.
Some are young -- Himalaya and Andes
Some are old -- Appalachians
Some are really old -- CONTINENTAL SHIELD
Shield areas generally are so old that they have
been eroded flat.
Local example includes the Canadian Shield.
Forms the core of North America.
FOLDS, FAULTS & MOUNTAIN BELTS
BUILDING MOUNTAINS
CONTINENTAL SHIELD (Canadian Shield)
Composed of highly deformed and metamorphosed
rocks.
Shield rocks
are eroded flat.
FOLDS, FAULTS & MOUNTAIN BELTS
BUILDING MOUNTAINS
CONTINENTAL SHIELD (Canadian Shield)
FOLDS, FAULTS & MOUNTAIN BELTS
OROGENESIS (Mountain Building)
Two main mechanisms
1. Volcanism
FOLDS, FAULTS & MOUNTAIN BELTS
OROGENESIS (Mountain Building)
2. Deformation and Uplift
A. Fold and Thrust Mountains
Produced by plate collisions.
Results in high mountain systems.
Usually marine sediments that become
highly folded and metamorphosed.
Commonly have igneous intrusions.
Examples include the Alps, the Himalaya,
the Urals and the Canadian Rockies.
FOLDS, FAULTS & MOUNTAIN BELTS
OROGENESIS (Mountain Building)
2. Deformation and Uplift
Fold and Thrust Mountains
FOLDS, FAULTS & MOUNTAIN BELTS
OROGENESIS (Mountain Building)
2. Deformation and Uplift
B. Fault Block Mountains
Bounded by high angle normal faults.
Produced by tensional forces.
Horsts and grabens common.
Examples include the Great Basin of the
western United States.
FOLDS, FAULTS & MOUNTAIN BELTS
TYPES OF FAULTS
HORSTS AND GRABENS
FOLDS, FAULTS & MOUNTAIN BELTS
OROGENESIS (Mountain Building)
2. Deformation and Uplift
C. Upwarped Mountains
Large area of continent is domed up.
Very little deformation of rocks.
Located far from plate boundaries.
Not exactly sure how they form.
Example: Adirondack Mountains, NY
FOLDS, FAULTS & MOUNTAIN BELTS
OROGENESIS (Mountain Building)
C. Upwarped Mountains
Adirondack Mountains, NY
EARTHQUAKES
EARTHQUAKE
A sudden release of energy accumulated in deformed
rocks causing the ground to tremble or shake.
Causes rupturing or brittle failure of crustal rocks.
Energy is released.
Movement of fault blocks takes place along a
fault plane.
EARTHQUAKES
After energy is released, friction between the adjacent
fault blocks prevents further movement.
Stress resumes and builds up again.
Friction between the blocks is overcome.
Another earthquake occurs.
EARTHQUAKES
FOCUS or
HYPOCENTER -Precise underground
spot at which rocks
begin to break or move.
EPICENTER -The point on the Earth’s
surface directly above
the focus.
EARTHQUAKES
AFTERSHOCKS are continued shaking of the Earth
after an earthquake that results from the rocks
trying to find a new equilibrium in new positions.
EARTHQUAKES
SEISMIC WAVES
When rocks break in an earthquake, energy is released.
The energy released has high velocity and moves rapidly
though the adjacent rocks.
Energy is transmitted via SEISMIC WAVES.
These waves are generally low frequency sound waves.
Generally they are so low that we can’t hear them.