8th Grade Science Test 2

Question 1

the most abundant element in the earth’s crust

Answer 1

oxygen

Question 2

in what type of fault do rocks along one side of the fault move horizontally along the fault

Answer 2

strike-slip fault

Question 3

85% of all earthquakes are

Answer 3

shallow-focus earthquakes

Question 4

a bowl-shaped hollow more than 2 miles wide, formed by the collapse of an underground magma chamber

Answer 4

caldera

Question 5

the point deep in the earth at which an earthquake begins

Answer 5

focus

Question 6

the large almond- or teardrop-shaped pieces of ejecta formed when lava solidifies

Answer 6

volcanic bomb

Question 7

the narrow zone of active volcanoes that nearly encircles the Pacific basin

Answer 7

Ring of Fire

Question 8

About 80% of the world’s earthquakes occur

Answer 8

in the circum-Pacific belt

Question 9

the bending or buckling of rocks under great force produces

Answer 9

a fold

Question 10

the inner core of the earth is thought to be

Answer 10

solid

Question 11

an inactive volcano that can erupt again

Answer 11

dormant

Question 12

the middle of the earth’s three main layers

Answer 12

mantle

Question 13

an instrument used to record the vibrations caused by earthquakes

Answer 13

seismograph

Question 14

a large, well-known strike-slip fault in western California

Answer 14

San Andreas Fault

Question 15

the study of the earth

Answer 15

geology

Question 16

the study of earthquakes

Answer 16

seismology

Question 17

all the present-day continents are thought to have been one land mass called

Answer 17

Pangaea

Question 18

an earthquake caused by sudden movements of rock beneath the earth’s surface

Answer 18

tectonic earthquake

Question 19

a domelike igneous instrusion formed when magma bulges overlying rocks upward

Answer 19

laccolith

Question 20

type of volcano consisting primarily of erupted volcanic ash and rock fragments held loosely together

Answer 20

cinder-cone volcano

Question 21

broad, gently sloping volcano made of large quantities of highly fluid lava that hardened into rock

Answer 21

shield volcano

Question 22

volcano formed partly by explosive eruptions of ash and rock fragments and partly by mild lava flows

Answer 22

composite volcano

Question 23

theory that states that rocks spring back to a position of little or no strain at the moment of an earthquake, causing vibrations in the earth’s crust

Answer 23

elastic rebound theory

Question 24

the fastest type of earthquake waves

Answer 24

P waves

Question 25

small earthquakes that often follow a larger earthquake at frequent intervals for days or even months

Answer 25

aftershocks

Question 26

the most famous scale of earthquake strength, which rates earthquakes on a scale of 1-9

Answer 26

Richter scale

Question 27

deposits of sand and mineral fragments, usually laid down by water

Answer 27

sediments

Question 28

the underground ___ is the actual source of a volcanic eruption

Answer 28

magma chamber

Question 29

a sheetlike igneous intrusion formed when magma hardens in a vertical crack

Answer 29

dike

Question 30

type of mountain formed when molten rock collects beneath an overlying rock layer, forcing the layer upward into a blisterlike structure

Answer 30

domed mountain

Question 31

type of mountain formed when rocks on one side of a fault are forced upward and the rocks on the other side are forced downward

Answer 31

fault-block mountain

Question 32

type of mountain formed when molten rock erupts from a hole in the earth's crust

Answer 32

volcanic mountain

Question 33

type of mountain formed when two rock layers are pushed together, causing the layers to buckle

Answer 33

folded mountain

Question 34

the point on the earth's surface directly above the point where an earthquake begins

Answer 34

epicenter

Question 35

an archlike structure formed when rocks are folded upward

Answer 35

anticline

Question 36

the channel in a volcano through which gases, ash, and molten rock are ejected from the earth's interior

Answer 36

vent

Question 37

a superheated, incandescent cloud of gas and volcanic ash that flows swiftly down a volcanic slope

Answer 37

pyroclastic flow

Question 38

lava that hardens into rough, jagged rocks with a crumbly or "blocky" texture

Answer 38

aa lava

Question 39

a troughlike structure formed when rocks are folded downward

Answer 39

syncline

Question 40

lava that hardens into a smooth-textured rock with a "ropy" appearance

Answer 40

pahoehoe

Question 41

a particle or block of solid volcanic ejecta

Answer 41

pyroclast

Question 42

in what type of fault are rocks on one side of a fault shoved on top of the rocks on the other side

Answer 42

thrust fault

Question 43

a volcano that has erupted within recorded history or is currently producing seismic activity

Answer 43

active

Question 44

the central portion of the earth

Answer 44

core

Question 45

Where are the effects of an earthquake most severe?

Answer 45

epicenter

Question 46

In what kind of fault do rocks along one side of the fault sink vertically?

Answer 46

normal fault

Question 47

What is the boundary line between the crust and the mantle called?

Answer 47

Mohorovicic discontinuity (Moho)

Question 48

What is molten rock beneath the surface of the earth called?

Answer 48

magma

Question 49

What theory states that the earth's crust and upper mantle consist of huge plates slowly drifting because of convection currents in the mantle?

Answer 49

plate tectonics

Question 50

What is the area between the upper mantle and the lower mantle called?

Answer 50

transition zone

Question 51

What is an underground channel that formed when surface lava hardened before the lava underneath it?

Answer 51

lava tunnel

Question 52

Compare and contrast fixed-base systems, base-isolated systems, and energy-dissipation devices.

Answer 52

A fixed-base system is a type of foundation in which the building is attached to bedrock; the energy of an earthquake is absorbed by the building's frame and joints. A downside to this system is that the building may be deformed. Base-isolated systems are the most common new construction for earthquake resistance. In a base-isolated system, the building is on stiltlike isolators, which separate the building from the foundation and absorb seismic energy. Energy-dissipation devices are added to structures to absorb seismic energy, lessening the stress on the building and thereby minimizing deformation.