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Terms in this set (58)
A molten mixture of rock-forming substances, gases, and water from the mantle
formed by melting pre-existing rock in Earth's interior
Liquid magma that reaches the surface; also the rock formed when liquid lava hardens.
CYU VO.1 Check Your Understanding
For magma to rise through the crust it must be (choose all that apply)
A) Cool enough to solidify
B) Runny enough to flow
C) Less dense than the crust
D) Full of gas bubbles to float
E) More dense than the crust
F) Hot enough to stay liquid
Chemical, mineralogical, and physical composition of magma
a naturally occurring, inorganic solid that has a crystal structure and a definite chemical composition
a mineral that contains a combination of silicon, oxygen, and one or more metals
Igneous rock that forms when magma hardens beneath Earth's surface.
Igneous rock that forms from lava on Earth's surface
a mass of flowing or solidified lava.
A hot, fast-moving type of lava that hardens to form smooth, rope like coils
rubble-y flow top consisting of broken fragment of lava
rock that forms when lava cools too quickly to form crystals
volcanic glass if it is massive
A type of igneous rock that contains air bubbles
The volcanic rock ejected during an eruption, including ash, lapilli, bombs, and blocks
<2 mm diameter pyroclastic material
2-64 mm pyroclastic material
>64 mm pyroclastic material
blocks and boms
H2S - egg smell
factors influencing explosively of magma
high gas content
resistance to flow
factors influence viscosity
exist at high tempretures, have the lowest viscosity, have low gas contents, and tend to erupt effusively
dark in color, dense, majority are extrusive
erupt at relatively low temperatures and high viscosities
lighter-coloured felsic rocks
CYU VO.2 Check Your Understanding
High viscosity encourages high explosivity because ______.
A) gas content decreases viscosity
B) gas content increases viscosity
C) bubbles have trouble growing in highly viscous magma
D) highly viscous magma lets gas escape
E) highly viscous magma lets bubbles grow and pressure goes up
the sequence of events leading to an explosive eruption
1. high silica magma forms in the crust by melting of pre-existing rock
2. the magma rises towards Earth's surface
3. vesiculation occurs
4. the magma cooling as it rises + viscosity increasing --> the gas bubbles are trapped in the viscous magma
5. the bubbles in the magma is about 75%
As the magma rises, the dissolved gas expands and forms ubbles in the magma
Types of Volcanoes
mafic volcnic landforms
intermediate to felsic volcanic landforms
Mafic volcanic landforms
Shield volcanoes and cinder cones
a broad, domed volcano with gently sloping sides, characteristic of the eruption of fluid, basaltic lava.
a small, conical volcano built of ash and cinders.
Intermediate to felsic volcanic landforms
Stratovolcanoes (composite volcano)
a volcano built up of alternate layers of lava and ash.
Tabular intrusions known as dykes and sills
intermediate but more SiO2 rick than andesite
Felsic volcanic landform
a large crater caused by the violent explosion of a volcano that collapses into a depression
CYU VO.3 Question for Further Thought
If you had a choice, which type of volcano would you AVOID living next-door to? Why?
C) shield volcano
D) cinder cone
Eruptive Volcanic Hazards
pyroclastic material (tephra)
small explosive eruptions
CYU VO.4 Question for Further Thought
How can we reduce the risk of damage by lavas?
A) build barriers and/or dams before an eruption
B) prevent development in valleys
C) divert or attempt to slow active lava flows
D) evacuate residents or move towns and villages away from volcanoes
E) prevent development by making the area around the volcano a National Park
CYU VO.5 Question for Further Thought
Which of the following are HAZARDS to people from ash fall? (choose all that apply)
A) Breathing in ash
B) Blanket of ash (like snow) on everything
C) Electrical fires
D) Total darkness (even during daylight)
E) Extra weight on roofs
F) Aircraft engines sucking in ash
G) Buildings destroyed by a fast-flowing or fast-falling ash
turbulent mixtures of hot gas and pyroclastic fragments that are emplace laterally from a volcanic vent
Sand-sized pieces of rock
CYU VO.6 Check Your Understanding
Which statement about pyroclastic flows is FALSE?
A) Pyroclastic flows can travel up to 200 km/h.
B) Pyroclastic flows can be as hot as 1,500 °C.
C) Pyroclastic flows can form from a collapsing lava dome.
D) Pyroclastic flows can flow uphill.
E) Pyroclastic flows contain pumice, ash, chunks of lava dome, and high temperature gas.
destructive mixtures of water, ash, rock fragments of all sizes
When a volcano becomes structurally unable to support its own mass, a large portion of the volcano can fail catastrophically.
Very rapid and turbulent mass wasting of debris, air, and water.
Volcanic Explosivity Index
volume of ash produced, height of eruption cloud, duration of eruption, 0-8 factor of ten, Based upon tephra volume. Objective eruption magnitude
CYU VO.7 Question for Further Thought
Why do you think scientists use eruption plume height as a basis for VEI? It is a good estimate of the ______.
A) volume of the eruption
B) power of the eruption
C) heat involved in the eruption
D) length of the eruption
E) area affected by the eruption
CYU VO.8 Check Your Understanding
Given a simplified Hazard Map for a stratovolcano (as shown below) and this key to the various hazard zones:
A) ash fall
B) pyroclastic flow
D) lava dome
E) lava flows
Zone A covers the largest area and follows the wind direction?
Zone B only covers the periphery of the volcano within less than 20 km from the summit?
Zone C follows river/stream valleys over extended distances downslope from the volcano?
Zone D, like Zone B, covers the periphery of the volcano's flanks but unlike Zone B, covers only areas within short distances from the summit?
Zone E, like Zone C, flows along river/stream valleys but unlike Zone C, covers only short distances from the summit?
Facets of Eruption Prediction
1. Collect existing geologic data
2. Develop a monitoring scheme
Volcano Monitoring Techniques
volcano Monitoring Strategy
Rising magma typically will
- trigger swarms of earthquakes and other types of seismic events
- cause swelling or subsidence of a volcano's summit or flanks
- lead to the release of volcanic gases
volcano Monitoring Strategy
1. increased seismic activity
a. Seismic monitoring
b. Acoustic flow monitors (AFM)
2. Ground deformation