Mountain Types June06

7/27/2019 Mountain Types June06

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Mountain orogeny

Geog 3251 Mountain Geography

Adina Racoviteanu


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Three types of plate boundary


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ORIGIN OF MOUNTAINS

Orogeny= process of mountain building,takes tens of millions of years; usually

produces long linear structures, known as

orogenic beltsTwo main processes:

1) Deformation: continental collisions, resulting in

folding and thrust-faulting

2) Volcanic Activity

Other processes:

Metamorphism, intrusions: batholiths, etc.


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TYPES OF MOUNTAINS

(according to their origin)

Fault-block: tension, normal faulting

Folded: compression, reverse faulting

Volcanic: Shield and composite

Complex: mixture of most of the above


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HANGING WALL

1. Fault-block mountainslarge areas widely broken up by faults

Force: TENSIONFootwall moves up

relative to hanging

wall

Normal fault


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Tilted fault-block range: Sierra Nevada from east,

Steep side of block fault; Ansel Adams photo


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Tilted Fault-block

Sierra Nevada from west

Side, low angle

Yosemite valley the result

Of glaciation on low-angle

relief

Central cores consists of

intrusive igneous rocks

(granite).

Half Dome is a core (batholit)

that was exposed by erosion,

Batholith


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Wasatch Range

From Salt Lake City

Typically fault-

Block system


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Grand Tetons: another fault-block system


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Alternating normal faults lead to a characteristic pattern called a

horst and graben system. An area under tension will often have

multiple mountain ranges as a result.

Horst and graben


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Horst and Graben Landscapes

Figure 12.14


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tilted fault-block

mountains in Nevada

result of a horst and

graben system

Nevada is under tension

because of rising magma

which is unzipping the

system, all the way from

Baja California

Sierra Nevada and Wasatch Ranges part of this system

Basin and Range province:


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Reverse fault

Force: COMPRESSIONHanging wall moves up

relative to footwall

Two types:

-low angle-high angle

Individual layers can move 100s of kilometers

Alps are a great example

Fl i


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Flatirons

Classic example of

high-angle reverse faults-> Form Sawtooth Mtns

due to differential erosion

Seal rock


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Thrust faults main cause of foldedmountains

3. Folded mountainsnappe (fr.) =

table cloth

Where rock does not fault it folds,

either symmetrically or asymmetrically.

upfolds:anticlines

downfolds:synclines


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Classic folded terrain: well-developed anticline


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Appalachian Mountains of the US


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Atlas Mountains, Northern Africa


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Zagros Crush Zone

AlternatingAnticlines and

Synclines


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White Cloud peak

SAWTOOTH RANGE,

IDAHO

Alice Lake


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3. Volcanic mountains

2 types of volcanoes:

Shield volcanoes

Composite volcanoes


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Shield volcanoes

-Compressive forces

-Basaltic composition

At hot spotsgentle-sloping

basaltic lava flows


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Mauna Kea

Shield volcano

Hot Spot

Basalt

Mauna Loa in

Background

Kilaeua isBehind Mauna

Loa


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Composite volcanoes

-andesitic composition

-steep cones, explosive

Encountered at subduction zones


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Mt Rainier:

example of composite volcano

G Pi hi h E d


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Guagua Pichincha, Ecuador

Quito in foreground

Composite volcanoes explosive


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Why do shield and composite volcanoes differ in

composition?

Basaltic magmas rise along fractures through the basaltic

layer. Due to the absence of granitic crustal layer,

magmas are not changed in composition and they form

basaltic volcanoes.

Mountainous belts have thick roots of granite rock.

Magmas rise slowly or intermittently along fractures in the

crust; during passage through the granite layer, magmas

are commonly modified or changed in composition and

erupt on the surface to form volcanoes constructed of

nonbasaltic (andesitic) rocks.


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continental-continental collision

tend to have a little of everything:volcanoes,folds, thrust faults, normal

faults

4. Complex Mountains


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ALPS

HIMALAYAS

View of Everest and

Khumbu ice fall from

Kala Patar, Nepal

Himalayas


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ANDES:

classic example of

orogenic beltcordillera

NASA satellite image

View from Nev. Pisco,

Cordillera Blanca


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ANDES: CLASSIC EXAMPLE OF GENERIC MTNS

A) C i i


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A) Compression causes expansion

B) Layered rock formed

C) Thrust-faulting

D) Igneous intrusions: Plutons

E) Underplating

F) Regional metamorphism

South American Plate


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ANATOMY OF AN OROGENIC BELT


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Mountain orogeny summary

Orogeny = mountain building

Plate tectonics used to explain mountain building

Plate collisions- 3 types:

oceanic-oceanicoceanic-continental

continental-continental

Forces: tension, compression, shear

Mountain types: faulted, folded, volcanic, complexKnow examples of each

Mountain Types June06

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