14. Geohazards: Volcanoes And Earthquakes

Question 1

tsunami

Answer 1

a large ocean wave triggered by an earthquake or other natural disturbance

Question 2

geohazard

Answer 2

a hazard posed to people by the physical earth

Question 3

active volcano

Answer 3

a volcano that has erupted during the last 10,000 years and is likely to erupt again

Question 4

extinct volcano

Answer 4

a volcano that has not erupted for tens of thousands of years and can never erupt again

Question 5

stratovolcano

Answer 5

a large, potentially explosive cone-shaped volcano composed of alternating layers of lava and pyroclast

Question 6

pyroclast

Answer 6

any fragment of solid material that is ejected from a volcano, ranging in size from ash to large boulders

Question 7

ash (volcanic)

Answer 7

fine volcanic powder consisting of pulverized rock particles and solidified droplets of lava

Question 8

shield volcano

Answer 8

a broad, domed volcano formed from many layers of basaltic lava

Question 9

cinder cone

Answer 9

a small, cone-shaped volcano consisting of pyroclasts that settle at the angle of repose

Question 10

angle of repose

Answer 10

the steepest angle at which loose sediments can settle

Question 11

pãhoehoe

Answer 11

a lava flow with low viscosity and a smooth, glassy, or ropy surface

Question 12

‘a’ā

Answer 12

a mafic lava flow with a rough, blocky surface

Question 13

lapilli

Answer 13

marble- to golf ball- sized cooled fragments of lava

Question 14

pumice

Answer 14

a lightweight, porous rock with at least 50% air content, formed from felsic lava

Question 15

bomb (volcanic)

Answer 15

a streamlined fragment of lava ejected from a volcano that cooled and hardened as it moved through the air

Question 16

block (volcanic)

Answer 16

a fragment of rock from the volcano’s cone that is ejected during an explosive eruption

Question 17

joint

Answer 17

a crack or weak plane in rock

Question 18

columnar jointing

Answer 18

a geometric pattern of angular columns that forms from joints in basaltic lava during cooling

Question 19

large igneous province (LIP)

Answer 19

an accumulation of flood basalts that covers an extensive geographic area

Question 20

caldera

Answer 20

a large depression that forms when a volcano’s magma chamber empties and collapses after the volcano erupts

Question 21

effusive eruption

Answer 21

a nonexplosive eruption that produces mostly lava

Question 22

volcanic explosivity index (VEI)

Answer 22

an index used to rank volcanic eruptions based on the amount of material a volcano ejects during an eruption

Question 23

lahar

Answer 23

a thick slurry of mud, ash, water, and other debris that flows rapidly down a snowcapped stratovolcano when it erupts

Question 24

pyroclastic flow

Answer 24

a rapidly moving avalanche of searing hot gas and ash

Question 25

normal fault

Answer 25

result of tensional force as two fault blocks move apart, causing one fault block to slip downward in relation to the other fault block

Question 26

reverse fault

Answer 26

result of compressional force as two fault blocks are pushed together, causing one block to move upward in relation to another block

Question 27

strike-slip fault

Answer 27

result of shearing force as one block moves horizontally in relation to another block

Question 28

fault scarp

Answer 28

a cliff face resulting from the vertical movement of a reverse or normal fault

Question 29

focus

Answer 29

location of initial movement along a fault during an earthquake

Question 30

epicenter

Answer 30

location on the ground’s surface immediately above the focus of an earthquake, where earthquake intensity is usually greatest

Question 31

aftershock

Answer 31

a small earthquake that follows the main earthquake

Question 32

seismograph

Answer 32

an instrument used to detect, measure, and record ground shaking

Question 33

modified Mercalli intensity (MMI) scale

Answer 33

an earthquake ranking system based on the damage done to structures

Question 34

liquefaction

Answer 34

transformation of solid sediments into an unstable slurry as a result of ground shaking during an earthquake

Question 35

moment magnitude scale

Answer 35

an earthquake ranking system based on the amount of ground movement produced