Geo100G Chapter 5

eruptions of lava from cracks in the earth's surface, as opposed to from single vents, are called _____________ _____________

fissure eruptions

carbon monoxide, carbon dioxide, fluorine, sulfure compounds, and water vapor are all ____________ emitted by volcanoes

gases or volatiles

while lava usually is not life threatening, it is _______________ enough to burn and destroy any property it encounters

hot

how does volcanic ash and dust cause cooling of the climate

it blocks sunlight from reaching earth

how will a large amount of volcanic ash and dust from a single large eruption effect global climate

it will cause regional or global cooling for months up to a few years

a fast-moving volcanic mudflow created through the combination of ash and water is called a _______________

lahar

the Volcanic Explosivity Index is a way to categorize the size of eruptions based on three categories which include the volume of _____________ produced

pyroclastics

where does the majority of volcanic activity occur

seafloor spreading ridges

earthquakes, harmonic tremors, and changes in topography and gas emissions are all precursor to volcanic _____________

activity

most of the world's active volcanoes are located _____________

along plate boundaries

Volcanic ________ can bury cities, it is slippery, it can cause roofs to collapse, is bad for people's lungs, and is damaging to engines and other mechanical equipment

ash

what is the primary hazard of concern associated with the stratovolcanoes in the Aleutians

ash causing aviation hazards

a very large volcanic crater is known as a(n)

caldera

formed by either the collapse of a volcano into an emptied magma chamber or the enlargement of an existing crater, a __________ represents a very large volcanic eruption

caldera

a relatively small and steep volcano, a ____________ __________ is made of pieces of basaltic magma thrown into the air near the vent due to the escape of dissolved gases

cinder cone

this symmetric volcano made of pieces of magma thrown into the air by the escape of dissolved gasses is called a _____________

cinder cone

evacuations necessitated by impending volcanic eruptions have saved significant numbers of lives, yet they can be seen as inconvenient and disruptive because

volcanoes don't always erupt in the time and fashion they were expected to

of all the gases listed below that are emitted by volcanoes, which is the primary

water vapor

how many active volcanoes are present in the world

300-500

which of the following commonly precede a volcanic eruption

-changes in the volcano's shape -changes in gas emissions -seismic activity

how is volcanic activity associated with landslides

-earthquakes associated with moving magma may cause landslides -landslides may allow volcanic gases to escape -steep and/or coastal volcanoes may have materials that are weakened and fail suddenly

which of the following describe a pyroclastic flow

-it is a very dangerous volcanic hazard -it is also known as a nuée ardente

choose all of the hazards associated with volcanic ash

-it is dangerous to breathe since it is composed of microscopic glass -it can bury entire cities -it causes mechanical failures

what are the two primary controls on magma composition

-the parent material -the extent of melting

which of the following describe the volcanoes of the Cascade Range

-they are composite volcanoes -they are created through the process of subduction

which of the following describe lahars

-they are made of ash and water -they move quickly

which of the following describe stratovolcanoes

-they are made up of both pyroclastic and lava flow layers -they are known to erupt explosively -they are also known as composite volcanoes

lava is typically _________ or hotter

850 degrees Celsius

the largest volcano on earth, ___________ ____________ is a type of shield volcanoes, those are created from hundreds to thousands of runny basalt flows

Mauna Loa

which of these volcanoes in the Cascades is the most recently active

Mount St. Helens

many of the world's active volcanoes are located along the rim of the ______________

Pacific Ocean

what is the acronym for the scale used to rank the size of volcanic eruptions based on the volume and height of pyroclastics released, as well as the length of the eruption?

VEI (Volcanic Explosivity Index)

which of these best describes the current state of worldwide volcano monitoring

many active volcanoes are actively monitored

magma composition is controlled by the type of _______________ that is being melted and the extent to which it is melted

material

fissure eruptions occur ___________ and can result in massive outpourings of basalt

on continents or on the seafloor

water that is heated because it is near magma may cause a volcanic eruption called a(n) ___________________

phreatic eruption

when a volcano erupts due to the creation of large amount of steam, it is called a

phreatic explosion

a very hot, very fast-moving flow of hot gases and ash from a volcano is known as a(n) _____________

pyroclastic flow

what type of volcano is produced from fluid basalt flows that create a large, broad, gently sloping structure

shield volcano

the volcanoes of the Aleutian Islands are _________ volcanoes that are ____________ in composition

strato-; andesitic

what type of volcano is composed of both pyroclastic and lava flow layers

stratovolcano

landslides may lead to volcanic eruptions when _________.

the removal of material allows gases to escape

seafloor spreading ridges are the most volcanically active areas on earth's surface because ________________

they are so widespread