GENERAL GEOLOGY (OROGENY & MOUNTAIN BELTS) Flashcards
Young Mountain Belts in the World
NA Cordillera (Capehorn - Alaska)
Andes
Alpine-Himalaya
Atlas
Alps
Caucasus
Zagros
Tien shan
Himalayas
West Pacific Mountaunous Terrain
What is the meaning of Cordillera
“Spine” or Back bone
Age of Himalayas
50 Ma
Old Moutain Belts
Appalachians (E. US)
Urals (Russia)
Caledonian Sz
Altay Sayan China
Great Dividing Ranges (aus)
Processes that collectively produce mountain belt
Orogenesis “Oros” Mountains
Type of subduction for Island Arc type orogey
Ocean-Ocean
Andean Type
Continental-Ocean
Continental Margins where sedimentation has produced a thick platform of shallow water sandsones, limestones and shales
it will be peeled or cut off from the descending plate and thrust (Accrete to the adjacent continental blocl)
Depth of partial melting by devolatilization and inducing of fluid at subduction zones
100 kilometers
Partial melting of Ultramafic Rocks produces this kinds of Magma
Primary Magma (Basaltic)
After primary melting what happens next?
Basaltic magma which is less denser will rise and will pond below continental crust
Then afterwards?
Through magmatic differention, a basltic magma can generate low density felsic or intermediate secondary magma which can rise through the continental crust
In continental-oceanic volcanic arcs what proceeds after subduction?
Uplift
Why does continental crust impedes the ascent of molten rock?
Because of its density and great thickness
When a magma intrudes the crust and crystallizes at depth it forms
Batholiths
Resulting chaotic accumulation of deformed and thurst faulted sediments and scraps of ocean crust
Accretionary wedge
Since the accretionary wedge acts as a barrier for sediments from the Volcanic Arc to the trench, it forms an accumulation of sediments in between the accretionary wedge and the volcanic arc which is realatively undeformed
Forearc Basins
Proto Pacific Plate
Farallon Plate
Example of A volcanic Arc system
Sierra Nevada - Volcanic Arc
Great Valley - Forearc Basin
Coast Ranges -Accreationary Wedge
Terrain vs Terrane
Terrane (E for evolved)- A crustal fragment with distinct and recognizable series of rock formations transported by Plate Tectonics Processes
Terrain - Shape of the surface topography or lay of land
A type of orogeny associated with Pacific like oceans in which Fast spreading rates is balanced by the high rate of subduction which make it unlikely to close but rather carry islands arcs or crustal fragments to collide with an active citinental margin through collission and orogeny
Cordilleran type Mountain building
Nature of terranes in the pacific
Microcontinents
Island Arc
Submerged Plateau
When the oceanic plate contains small seamounts (submerged) and meets and andean type subduction, what will most likely happen?
Submerged plateau will be consumed through the descending oceanic slab unless they are thick units or are mainly composed of light felsic minerals
When a crustal fragment accretes to the adjacent continental crust what would most likely happen?
It will be peeled or cut off from the descending plate and thrust (Accrete to the adjacent continental blocl)
This type of mountain building happends when two continental masses collide. (characterized by vertical thickening)
Alpine Type Mountain Building
Mountains formed by contintental collisions
Himalayas
Appalachians
Urals
Alps
The zone where two cotinents collide and are welded together and which is characterized by preserved slivers of oceanic lithosphere that were trapped between the colliiding plates
Suture zone
Earth’s youngest collisional mountains
Himalayas
Syaty of Himalayan Orogeny
Early Eocene
Highest elevation or mountain in the US
Mt.Whitney
A mechanism responsible for the formation of SE asia where the northward migration of india produced a lateral eastward displacement of crustal blocks
Contintental Escape
Supercontinent 750 Ma Mesoproterozoic
Rodinia
how many orogenic episodes does appalachian orogeny have?
3
What was the culmination of Pangaea Formation?
Allenghian Orogeny (250-300 Ma)
What was the three part Appalachian Orogeny?
Taconic
Acadian
Alleghanian
Orogeny which involves closing of the sea between East protoNAm (Laurentia) plate and a volcanic arc at 450 Ma Ordovician and which the now is reprecented by the metamorphic rocks of the western appalachian especially New York
Taconic Orogney
Closing of Northen Iapetus and collision of Baltica with Laurentia
Caledonian Orogeny
Second epidsode of mountain building when avalonia microcontinent colllided with N. America that closes southern Iapetus Ocean formation of laurasia (350 Ma Carboniferous)
Acadian Orogeny
Final orogeny which occurred 250-300 Ma (Permian) in which africa callided with north america as borders of Laurasia and Gondwana respectively which finally formed
Allenghanian Orogeny
Breaking of Pangeaa
180 Ma (Triassic)
This formed when Africa and two other crustal fragment collided upward with europe and closed Tethys Sea
Alps
This formed during the assemblage of Pangea when Northern Europe Collided with Northen Asia
Urals
Orogeny which formed the rocky mountains 60 yrs ago (Paleocene)
Laramide Orogeny
Whats the back arc of sierra nevada?
Colorado Plateau
Concept of floating crust in gravitational balance upon the material of the mantle
Isostasy
Whats the guiding principle of isostacy,
The higher the elvation the deeper its roots
Basta mataas kailangan mas malalim na base
Process of establishing new gravitational balance by loading or unloading
Isostatic Adjustment
What happens when mountains are eroded?
There will be uplift due to crustal rebound
This happens when the vertical pull of gravity surpasses the horizontal compression during collision and involves ductile spreading at deoth and normal faulting and subsidence in upper, brittle portions of Earth’s crust
Gravitational collapse
Airy’s Theory
Mountains have roots that extend into the mantle. The Deeper the roots the higher the mountains will be
Pratt’s Theory
Elevation is inversely proportional to density thus, higher mountains have lower densities