Quiz 5- Ch. 3/5/13

Question 1

Divergent boundaries

Answer 1

plates move apart, narrow rifts created, divergent boundaries within continents are more complicated and distributed over a wider area

Question 2

mid ocean ridge

Answer 2

An undersea mountain chain at a divergent boundary, characterized by earthquakes, volcanism, and rifting, all caused by the tensional forces of mantle convection that are pulling the two plates apart.

Question 3

spreading center

Answer 3

A divergent boundary, marked by a rift at the crest of a mid-ocean ridge, where new oceanic crust is formed by seafloor spreading

Question 4

magnetic anomaly

Answer 4

One in a pattern of long, narrow bands of high or low magnetic intensity on the seafloor that are parallel to and almost perfectly symmetrical with respect to the crest of a mid-ocean ridge.

Question 5

relative plate velocity

Answer 5

The velocity at which one lithospheric plate moves relative to another.

Question 6

2 geometric principles that govern the behavior of plate movement

Answer 6

transform-fault boundaries indicate the directions of relative plate movement

Seafloor isochrons reveal the positions of divergent plates at earlier times

Question 7

porphyry

Answer 7

An igneous rock of mixed texture in which large crystals (phenocrysts) “float” in a predominantly fine-grained matrix.

Question 8

Extrusive Igneous rocks

Answer 8

Lavas: volcanic rock that ranges in appearance from smooth and ropy to sharp and spiky depending on the conditions

Pyroclasts: fragments of lava are violently erupted and thrown into the air

Question 9

Felsic rocks

Answer 9

are poor in iron and magnesium and rich in minerals that are high in silica. i.e. granite

Question 10

mafic rocks

Answer 10

contain large proportions of pyroxenes and olivines. These minerals are relatively poor in silica but rich in magnesium and iron i.e. gabbro

Question 11

partial melting

Answer 11

Incomplete melting of a rock that occurs because the minerals that compose it melt at different temperatures.

Question 12

decompression melting

Answer 12

The spontaneous melting of rising mantle material as it reaches a level where pressure decreases below a critical point, without the introduction of any additional heat

Question 13

magma chambers

Answer 13

magma-filled cavities in the lithosphere that form as rising pools of melted rock push aside surrounding solid rock

Question 14

Earthquake

Answer 14

The violent motion of the ground that occurs when brittle rock under stress suddenly breaks along a fault.

Question 15

elastic rebound theory

Answer 15

stressed rocks are strained elastically, so that when a fault breaks, the rocks on either side of the fault return to their undeformed, stress-free shape.

Question 16

fault slip

Answer 16

The distance of the displacement of the two blocks of rock on either side of a fault that occurs during an earthquake