Volcanoes Flashcards
Igneous rocks form as _____ rocks _____ and ______
- molten
- cool
- solidify
intrusive/plutonic rocks
rocks that crystallize at depth
extrusive/volcanic rocks
magma that reaches the surface
Magma consists of which 3 components?
- melts
- solids
- volatiles
solids are generally _______ that have already _______ from the melt
- silicate minerals
- crystallized
volatiles
gases dissolved in the melt
rocks in the lower crust and upper mantle are near their _____ and any extra heat may induce ______
- melting points
- melting
an ______ in confining pressure causes an ______ in a rock’s melting temperature
increase
when confining pressures drop, _____ occurs
decompression melting
most volcanoes are located within or near ______
ocean basins
the main source of basaltic magma is
spreading centres slong mid-ocean ridges
hot spots form ______ sources in oceanic crust and ______ sources in continental crust
- basaltic magma
- felsic magma
magma at depth is ____ dense than the surrounding rock
less
magma differentiation
• Separation of a melt from earlier formed crystals to form a different magma composition
assimilation
Changing a magma’s composition by incorporation of foreign matter (country rock) into a magma
fractional crystallization
progressive changes in the chemistry of slowly cooling magma because of sequential crystallization of different minerals
batholith
- largest intrusive body
- frequently form the cores of mountains
Largest known eruption
Yellowstone, 2500 km3
shield volcanoes are _______ and composed primarily of _______
- broad and slightly dome-shaped
- basaltic lava
shield volcanoes are produced by
mild, eddusive eruptions of large volumes of lava
composite/stratovolcanoes are ______
large, classic-shaped volcanoes
cinder cones are built from _______, are ______ in size, and frequently occur in ______
- ejected lava
- small
- groups or on flanks of other volcanoes
domes are a _____ mass of ______, and can block openings leading to _______ of _______ magma
- bulbous
- congealed
- explosive eruptions
- gas-rich
crater
steep-walled depression at the summit, generally <1 km diameter
vent
opening connected to the magma chamber via a pipe
caldera
- large depression at the summit of a volcano
-formed when magma is
withdrawn/erupted from a shallow underground magma reservoir
as magma reaches Earth’s surface, which 3 things occur?
- crystallisation
- fractionation
- exolution of volatiles
Which factors control eruptive style by increasing explosivity?
- silica content
- volatile content
- high viscosity
Subduction zones can be _____ and _____
- continental/oceanic
- oceanic/oceanic
rift zones/spreading centres and hot spots can be _____ and _____
- oceanic
- continental
Lava flows move _____ and reach temperatures of _____
- slowly
- 500 to 1,000 degrees C
Aa basaltic lava has ____ viscosity, _____ texture, and forms _____ surfaces
- high
- blocky
- rough
Pahoehoe basaltic lava has _____ viscosity, _____ texture, and forms ______ surfaces
- low
- ropey
- smooth, unbroken
eruption columns can ______ and have potential _____ effects
- collapse
- climatic
tephra fall is transported by _____, causes _____ collapse, ______ illness, and lead to ______
- wind and rain
- building
- respiratory
- lahars
ash impacts _____
airplanes
pyroclastic flows have ____ velocity and temperatures of ______
- high
- 100 to 800 degrees C
What is the most direct cause of death in eruptions?
pyroclastic flows
lahars are hyperconcentrated __________, have _____ density, are highly _____, and can occur ________ an eruption
- volcanic mudflows
- high
- erosive
- during or after
Landslides are caused by
- magma intrusion
- explosive eruption
- gravitational collapse
- earthquake
tsunmis are responsible for _____ percent of volcano-related fatalities
25
volcanic gases are directly responsible for ___ perfect and indirectly responsible for ___ percent of volcano-related fatalities
- 3
- 40
How do volcanic gases cause death?
- crop destruction
- starvation
- disease
Volcano monitoring methods
- seismic
- ground deormation
- microgravity
- geochemical
- thermal
We can prevent volcanic hazards by _____ lahars, _______ lava flows, and avoiding building in ______
- canalizing
- water and solidifying
- high-risk zones
The Nevado del Ruiz eruption was _____ but had a ______ death toll
- small
- large
the Mt. Pinatubo eruption was _____ but had a ______ death toll
- large
- smaller
