chapter 15 volcanoes and earthquakes Flashcards
tsunami
large ocean waves triggered by an earthquake or other natural disturbance of the ocean floor
in 2004 the seafloor near ____ in ______ moved upward of 5 m
sumatra
indonesia
magma
melted rock between the surface of the crust
active vs extinct volcano
active- a volcano that has erupted in the past 10 000 years and could erupt again
extinct- a volcano that has erupted for tens of thousands of years and can never erupt again
lava
magma that spills onto the surface of earths crust
4 types of volcanoes
- shield volcanoes
- stratovolcanoes
- cinder cones
- lava domes
shield volcanoes
a broad dome shape, with numerous layers of fluid basaltic lava laid down over tens to hundreds of thousands of years
magma chamber
the reservoir of magma beneath a volcano
volcanic vent
conduit through which magma moves and reaches the surface
stratovolcano
a large, potential explosive, cone shaped volcano composed of layers of lava and pyroclasts
pyroclast
any fragmented solid material that is ejected from a volcano
ash
pulverized rock particles and solidified droplets of lava that form a fine powder
lava dome
formed when thick lava cannot easily flow piles up around a volcanic vent and solidifies into a dome shape
cinder cone
small cone shaped volcanoes consisting of pyroclast
angle of repose
the steepest angle at which loose sediments can settle
mafic lava type
silica content 50% or less, low viscosity, darker in color
felsic lava type
silica content 70% or more, high viscosity, dominated of iron and silicon, produces volcanic domes
pumice
lightweight porous rock with at least 50% air content
lapilli
marble to golf ball sized cooled fragments of lava
lava bomb
fragments of lava ejected from a volcano that cools and hardens as it is moving through the air
volcanic block
fragment of rock that is torn from the volcano’s cone and ejected during an explosive eruption
volcanic gases (4)
water vapour, carbon dioxide, sulfur dioxide and hydrogen sulfide
joint volcanic landform
crack and weak planes in the rock
columnar jointing volcanic landform
a geometric pattern of jointing in volcanic rockfor hexagonal columns when cooled
large igneous provinces
accumulations of basaltic lava that covers extensive geographic areas
caldera
a large depression that forms when a volcano’s magma chamber empties and collapses
effusive eruption vs explosive eruption
effusive- a nonexplosive that produces mostly lava
explosive- sends rock, ash, and volcanic gases high into the troposphere or even into the stratosphere
volcanic explosivity index
ranks volcanic eruption magnitude based on the amount of material a volcano ejects during an eruption
two biggest threats from volcanoes
lahar- a thick slurry, of mud, ash, and other debris that moves rapidly down the volcanoes flank
pyroclastic flow- blazing cloud (up to 500 degrees), a quick moving (up to 700km/hr) avalanche of gas and ash
three basic types of faults
normal fault- tensional force pulls two pieces of earths crust apart
reverse fault- compressional force pushes two blocks together and upward in relation to another block
strike slip fault fault- occurs where one block moves horizontally in relation to another block as a result of a lateral force
seismograph
an instrument used to detect, measure, and record ground shaking
modified mercalli intensity scale
system used to rank the intensity of shaking during an earthquake
liquefaction
the transformation of solid sediment into an unstable slurry by ground shaking
