mountain building

Question 1

mountain building

Answer 1

• orogenesis (greek) oros = mountains, genesis = to come into being
• the process that collectively produce a mountain belt
• result of plate tectonics
• origin is plate boundaries

Question 2

mechanism 1. horizontal compressional forces

Answer 2

that have shortened and thickened the crust, producing folding and thrust faulting of preexisting sedimentary rocks and crystalline crustal fragments

Question 3

mechanism 2. horizontal tensional stress

Answer 3

• causes the upper crust to be broken along normal faults, while the lower crust deforms by ductile stretching
• as a result they form fault block mountains

Question 4

types of mountains

Answer 4

• unwarped mountains, ex black hills
• volcanic mountains, ex White Island
• fault block mountains, ex basin and range California
• folded or compressional, ex Himalayas

Question 5

features of subduction zones

Answer 5

1. deep oceanic trench
2. volcanic arch
3. forarch region
4. backarc region

Question 6

deep oceanic trench

Answer 6

• where two plates converge and one is subjected beneath the other
• a region where subjecting oceanic lithosphere bends and descends into the asthenosphere

Question 7

volcanic arc

Answer 7

• built upon overlying arch
• two types
  1. volcanic island arc, oceanic- oceanic plates convergence, ex Aleutian Islands. - basin between the arc and mainland
  2. continental volcanic arc, oceanic- continental plates convergence. - area on the continental behind the arc

Question 8

forearc region

Answer 8

between the trench and the volcanic arc

Question 9

backarc region

Answer 9

located on the side of the volcanic arc opposite of the trench

Question 10

island arc type mountain building

Answer 10

• steady subduction of oceanic lithosphere
• periodic volcanic activity, emplacement of plutons at depth, the accumulation of sediments scraped from the subduction plate, gradually increase the volume of the arc, resulting in mountainous topography.

Question 11

Andean type mountain building

Answer 11

• collision between continental and oceanic plates

- located along the active continental margins around Pacific Ocean

Question 12

stage 1

Answer 12

passive margin,

- accumulation of sediments

Question 13

stage 2

Answer 13

passive margin transforms into active margin

- beginning of subduction, compressional forces between two colliding plates deform rocks by bending and fracturing

Question 14

stage 3

Answer 14

building a continental volcanic arc, emplacement of plutons(batholiths)
-subduction and partial melting of mantle rock generates primary magmas

Question 15

stage 4

Answer 15

• development of an accretionary wedge
• an accretionary wedge is a chaotic accumulation of deformed sediments and scraps of oceanic crust
• prolonged subduction may thicken an accretionary wedge enough so it protrudes above sea level, forming a mountain

Question 16

stage 5

Answer 16

• formation of a forearm basin
• the growing accretionary wedge acts as a barrier to sediment from the arc to the trench
• it forms a region called a forearc basin of relatively undeformed layers of sediment and sedimentary rock

Question 17

stage 6

Answer 17

• subduction ends
• subduction ends and it is followed a period of uplift and erosion
• uplifting and erosion exposes batholith consisting of numerous erosion
• ex Sierra Nevada batholith - former volcanic arc
• California’s coast ranges constitutes the accretionary wedge
• great valley represents the remains of the forearm basin

Question 18

cordilleran type mountain building

Answer 18

• terranes
• place- subduction zone along active continental margin
• process- collision and merge ( or accretion) of large crustal fragments

Question 19

nature of terranes

Answer 19

-carry embedded oceanic plateaus, island arcs, and sea mountains
- plateaus or islands arcs may be too large and too buoyant toe subducted
- so they collide and merge ( or accrete) with continental margins
- accreted crustal blocks
once scattered throughout the eaters pacific as oceanic plateaus, islands arcs and sea mountains

Question 20

alpine type mountain building

Answer 20

continental collisions
- two lithospheric plates, both carrying continental crust
- result in the devolvement of compressional mountains
ex collision between Australian-indian and euro asian plates created himalayas mts. Himalayas are compressional mountains
- most compressional mountains exhibit a region of intense folding and thrust faulting called a fold and thrust belt

Question 21

suture zone

Answer 21

zone where two continents collide

Question 22

continental collisions major events event 1

Answer 22

passive continental margin converts into an active margin

Question 23

major event 2

Answer 23

subduction zone is born with an Andean type volcanic arc growing above it