The Solid Earth - Chapter 8: Mountain Building

Question 1

Give a couple examples of relatively young mountainous belts that have resulted from mountain building

Answer 1

American Cordillera
Alpine-Hamalayan Chain
The mountainous terrains of western Pacific (Japan, Phillipines, Sumatra)

Question 2

Some mountains, including the _____, began their growth as recently as 45 million years ago

Answer 2

Himalayas

Question 3

Give a couple of examples of older mountains that exhibit some of the same structural features found in the younger mountains

Answer 3

Appalachians

Urals (in the former Soviet Union)

Question 4

Mountain chains generally consist of roughly ____ ridges of folded and faulted _____ and _____ rocks, portions of which have been strongly metamorphosed and intruded by somewhat younger igneous bodies

Answer 4

parallel; sedimentary; volcanic

Question 5

In most cases, where were the sedimentary rocks associated with mountain chains formed?

Answer 5

Enormous accumulations of deep-water marine sediments as well as thinner shallow-water deposits

Question 6

For the most part, which type of rocks are older than the mountain building event?

Answer 6

Deformed sedimentary rocks

Question 7

At most modern day subduction zones, ____ are forming

Answer 7

volcanic arcs

Question 8

At sites where oceanic crust is being ____, continental blocks are also being rafted toward one another

Answer 8

subducted

Question 9

Recent studies indicate that the most important cause of orogenesis is ____

Answer 9

the collision of two or more crustal fragments

Question 10

Mountain building along continental margins involves the convergence of _____ and _____

Answer 10

oceanic plate

plate whose leading edge contains continental crust

Question 11

During the development of the volcanic arc, sediment derived from the land as well as that scraped from the subducting plate is plastered against the landward side of the trench. This chaotic accumulation of sedimentary and metamorphic rocks with occasional scraps of ocean crust is ____

Answer 11

accretionary wedge

Question 12

True or false: colliding plates cannot both be carrying continental crust

Answer 12

False; it is possible

Question 13

Because continental lithosphere is apparently too buoyant to undergo any appreciable amount of subduction, a collision between the __________ eventually results

Answer 13

continental fragments

Question 14

How were the Appalachians formed?

Answer 14

They were formed when a collision occurred between North America, Europe, and northern America

Question 15

How long ago were the Appalachians formed?

Answer 15

~300 mil years ago during which several distinct episodes took place

Question 16

Regarding the Appalachians, as the continental blocks began to converge, a _____ formed seaward of the ancient coastline of North America

Answer 16

subduction zone

Question 17

The igneous activity associated with the subduction zone RE: Appalachians forming (pre collision) gave rise to a __________

Answer 17

volcanic island arc

Question 18

The final _____ occurred about 250-300 mil years ago when Africa and Europe collided with North America.

Answer 18

orogeny

Question 19

RE: The Appalachian mountains associated… today these folded and faulted sandstones, limestones, and shales compose the essentially unmetamorphosed rocks of the ____

Answer 19

Valley and Ridge providence

Question 20

Briefly summarize the formation of the Appalachians or a similar complex mountain chain

Answer 20

1. after the breakup of a continental landmass, a wedge of sediment deposited along passive continental margins (increasing size of newly formed continent)
2. ocean basin begins to close and continents to converge
3. plate convergence = subduction of the intervening oceanic slab and initiates extended period of igneous activity… results in volcanic arc with granitic intrusions
4. debris eroded from descending plate adds to wedges of sediment along continental margins
5. eventually they collide which severely deforms and metamorphoses the sediments. They are then displaced along thrust faults
6. a change in the plate boundary ends the growth of the mountains. let erosion commence!

Question 21

Geologists refer to the crustal fragments whose geologic history is distinct from that of the adjoining ones as ____

Answer 21

terrane

Question 22

True or false: many modern microcontinents will eventually be accreted to active continental margins, thus resulting in the formation of new orogenic belts

Answer 22

True