WHAT IS OROGENY?Processes of mtn building

Distinctive patterns of depositioneugeocline, miogeocline

DeformationFolding and thrust-faulting

Metamorphism

Intrusions: batholiths, etc

Volcanic Activity

TYPES OF MOUNTAINS

• Volcanic: Shield and composite

• Fault-block: normal faulting and tension

• Folded: reverse faults and compression

• Complex: mixture of most of the above

Mauna Kea

Shield volcanoHot SpotBasalt

Mauna Loa inBackground

Kilaeua is Behind MaunaLoa

KilaeuaNewest ground inThe world

Asthenosphere comingTo the surface

Composite VolcanoMt Rainier

Compressive forcesSubduction zonesAndesitic composition

Guagua Pichincha, EcuadorQuito in foregroundComposite volcanoes explosive

Normal fault

Footwall moves Up relative toHanging wall

Tension forces

FOOTWALL

HANGING WALL

Tilted fault-block range: Sierra Nevada from east,Steep side of block fault; Ansel Adams photo

Tilted Fault-blockSierra Nevada from westSide, low angle

Yosemite valley the result Of glaciation on low-anglerelief

Wasatch RangeFrom Salt Lake City

Typically fault-Block system

Grand Tetons: Another fault-block system

Alternating normal faults lead to a characteristic pattern called aHorst and Graben system. An area under tension will often haveMultiple mountain ranges as a result.

Basin and range province: tilted fault-block mountains in Nevada.The results of a horst and graben system. Nevada is under tension Because of rising magma which is unzipping the system, all the wayFrom Baja California

Sierra Nevada and Wasatch Ranges part of this system

REVERSE FAULTS: Hanging wall moves up relative to footwallResult of compression: plates collidingTwo types: low-angle or thrust faults, and high-angle reverse faults

Individual layers can move 100’s of kilometersAlps are a great example

Thrust faults main cause Of folded mountains

Appalachian Mountains of the US

Atlas Mountains, Northern Africa

Classic folded terrain: well-developed anticline

ZAGROS MTSPERSIAN GULF

AlternatingAnticlines andSynclines

High-angle reverse faultsForms “Sawtooth Mtns”

Flatirons classic example

Sawtooth effect result ofDifferential erosion

White Cloud peak

SAWTOOTH RANGE,IDAHO

Alice Lake

COMPLEX MOUNTAINS

Tend to have a little ofEverything: volcanoes,Folds, thrust faults, normalfaults

ALPS

HIMALAYAS