Ch. 14

Question 1

sea floor spreading

Answer 1

midocean ridges are formed by currents of magma rising up from the mantle; volcanic eruptions create new basaltic ocean floor that then spreads away laterally fro the ridge. mid ocean ridges contain the newest crust formed.

Question 2

subduction

Answer 2

at oceanic trenches, older lithosphere descends into the asthenosphere where is is recycled. sediments furthers from the ridges are the oldest

Question 3

plate tectonics

Answer 3

a framework with which we can understand and relate a wide range of internal processes and topographic patters

Question 4

plates

Answer 4

move slowly over the asthenosphere. cold and rigid and therefore deformed significantly only at the edges and only where one plate interacts with another

Question 5

divergent plate boundaries

Answer 5

magma from the asthenosphere wells up in the opening between places, this upward flow of molten material produces a line of volcanic vents that spill out basaltic lava onto the ocean floor. plates move away. usually represented by a mid ocean ridge

Question 6

convergent boundary

Answer 6

plates collide and are sometimes referred to as destructive boundaries. removal or compression of the surface of the crust. mountain ranges, volcanoes, and oceanic trenches oceanic lithosphere is more dense than continental so it always under rides the continental plate

Question 7

oceanic-oceanic convergence

Answer 7

subduction also takes place, one plate goes beneath the other and a trench is formed. volcanic arc is typical here

Question 8

continental-continental convergence

Answer 8

no subduction takes place, forms mountain ranges,

Question 9

transform boundaries

Answer 9

two plates slip past each other, fault lines

Question 10

volcanism

Answer 10

a general term that refers to all the phenomena connected to the origin and movement of molten rock

Question 11

magma

Answer 11

molten material below the surface

Question 12

shield volcanos

Answer 12

basaltic lava tends to flow quite easily over the surrounding surface forming broad low lying shelf volcanos built up of later upon layer of solidified lava flow. little pyroclastic material, mountains with gentle sloping side

Question 13

composite volcano

Answer 13

emit higher silica “intermediate” lava such as andesite often erupt ant explosively and tend to develop into symmetrical steep sided volcanoes

Question 14

lava domes

Answer 14

plug domes, masses of very think viscous lava that does not flow very well. lava that bulges from a vent. some form inside of composite volcanoes.

Question 15

cinder cones

Answer 15

the smallest peak, cone shaped peaks built by the unconsolidated pyroclastic materials that are ejected from the vent.

Question 16

calderas

Answer 16

produced when a volcano explodes collapses or both. basin shaped depression that is generally circular that has a diameter many times larger than that of the original volcano

Question 17

folding

Answer 17

crustal rocks are subjected to stress, lateral compression the are deformed by being bent. anticline:symmetrical fold, ridges. syncline: down fold, valleys.

Question 18

diastrophism

Answer 18

deformation of the earths crust

Question 19

faulting

Answer 19

rock is broken with accompanying displacement. creates fault line, an area of weakness in the crust

Question 20

volcanic neck

Answer 20

pipe or throat of an old volcano that filled with solid lava