mountainbuilding-orogenesis07

8/18/2019 mountainbuilding-orogenesis07

1/32

Mountain Building - Orogenesis


2/32

Archimedes’ principle

Fig. 6.28

– The mass of the water displaced by the block of material equals the mass of the

whole block

– Thus for a material with a lower density

than water, the proportion of material abovethe water surface is constant

– For example wood (density 0.8 gm/cm) will

have 20% of its mass above water (density

of 1.0 gm/cm). Thus for a 1 m block 0.2 mwill be above water and 0.8 m below, but

for a 2 m block .4 m will be above water

and 1.6 m below


3/32

Isostasy & Mountain Roots

Fig. 6.29

– Continental Crust has “roots”

– As a result of isostacy, the thicker the surface exposure of rock, the thicker the

crustal “roots”

– As continental crust is compressed it shortens and thickens

– Avg. continental crust is 35-40 km thick, under deformed crust avg. is 50-70 km,with the majority of the difference in the “roots”


4/32

Fi . 6.31

Isostasy &

Mountain Roots


5/32

Mountain-Types

• Fault-Block Mountains

– Formed from tensional

stress – Normal Faulting

– Example: Basin and

Range Provinces SW

USA


6/32

Mountain-Types

• Upwarped Mountains – Formed from compressional stress – Broad arching of the crust or great vertical displacement

along faults

– Example: Black Hills SD


7/32

Mountain-Types

• Folded Mountains

– Formed from compressional stress

– Reverse Faulting and Folding – highly deformed rocks – Will have highly metamorphosed rocks

– Example: Appalachians, Himalayas


8/32

Mountain-Types • Volcanic Mountains – Formed volcanic activity

– Associated with plate boundaries or hot spots

– Example: Cascade Mts. Or

mountains within Japan


9/32

Mountain Building (Orogenesis)

Zones

Convergence Zones

Continental Collision

Continental Rifting


10/32

Convergence

Zones

• Oceanic-Continental – Folded Mt. Belts

– Thrust Faults

– Volcanic Chains

– Accreted Terranes – Example: Andes Mountains,

Cascades


11/32

Accreted Terranes

• As exotic blocks collidewith continents they become sutured to the

continent.

• The blocks are referred toaccreted terranes

• Accreted Terranes areisland arcs, portions ofocean floor, fragments ofcontinental crust


12/32

Convergence

Zones

• Oceanic-Oceanic – Volcanic Chains

– Examples:

Japan,Philippines


13/32

Collision Zones

• Folded Mt. Belts• Thrust Faults

• Remnants of Volcanic

Chains• Examples: Alps,

Himalayas


14/32

Continental Rifting

• Fault-block mountains


15/32

Mountain

Building –

Multiple

Events

Example:

Appalachian

Mountains


16/32

Mountain Building, Rock Cycle

and Plate Tectonics

Wh d h E h


17/32

Why does the Earth

have mountains of

various height?• Erosion attacks

mountains – remember

Earth wants to be flat• Orogenic collapse.


18/32

1-direction of the camera axis

2-combination of more than one

photograph

3-according to angle of coverage

4-on the basis of colour


19/32

camera ax s1-vertical photographs

2-horizontal or terrestrial photographs

3-oblique photographs


20/32

the surface of the earth.

2-it covers a relatively small area.

3-the shape of the ground area

covered on a single vertical photo

closely approximates a square orrectangle.

4-being a view from above, itgives an unfamiliar view of the

ground

5-distance and direction ma

t t t t


21/32

t eo o tes rom camera stat onon the ground.

2-these are used for survey ofstructures and mounments of

architectural or archaeological

value.


22/32

camera tilted fro, the vertical

2-these photographs cover large

areas of ground.

3-but the clarity of details

diminishes towards the far end ofthe phothgraph.

trape o a t o t t e p oto s


23/32

trapezo , a t out t e p oto ssquare or rectangular.

3-the objects have a morefamiliar view, comparable to

viewing from the top of a a high

hill or tall building.

4-no scale is applicable to the

entire photograph, and distancecannot be measured.

Parallel lines on the ground are

2 t e groun area covere s a


24/32

2-t e groun area covere s atrapezoid, but the photographis

square or rectangular.3-the view varies from the very

familear to unfamiliar, depending

on the height at which the

photograph is taken.

4-distances and directions are notmeasured on this photograph for

the same reasons that they are not


25/32


26/32

vertical and the side ones are

oblique.

2-this photography can be used

for rapid production of

reconnaissance maps on smallscales.

t roug t e ront no a po nt o


27/32

t roug t e ront no a po nt othe lens.

1-standard or normal angle photography- the angle of

coverage is of the order of 60

2-wide angle photography-the

angle of coverage is of order of

90/3-super wide angle-the angle of

coverage is of order of 120.

t ese p otograp s present t e


28/32

-t ese p otograp s present t eobjects as they appear in their

natural colour.-for good colour cintrast, scale

larger than 1:25000 is normally

used.

-it has better in terpretation

capabilities.-it is better ofr photogrammeric

studies.

n rare ra a ons w c are


29/32

- n rare ra a ons w c areinvisible to human eye have

wavelengths ranging from 0.7 umto about 1.6um.

-infrared photography can be

black and white or in colouir

depending on the type of film

used.


30/32

.-the differentiation between types

of healthy and unhealthy

vegetation is brought out in

distinctive colours.

-infrared colour with thecombination of panchromatic

capabilities.

p otograp y appears n g ter


31/32

p otograp y appears n g tertones on ir black and white

photographs.-water appears dark in ir black

and white because water has high

absorption characteristics in

infrared.

Yellow filter is used to reducehaze.


32/32

white negatives.

-dispositive are made from the

negatives and the four images are

combined in registration in an

additive colour viewer to producea true colour or a false colour

viewer to produce a true colour

or a false colour image on a

screen which can subsequently be

h t h d

mountainbuilding-orogenesis07

Documents