Volcano (VO)

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

oxygen
silicon
aluminum
iron
calcium
magnesium
sodium
potassium

titanium
manganese
phosphorus
hydrogen

a naturally occurring, inorganic solid that has a crystal structure and a definite chemical composition

silicate mineral

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

Volcanic Products

lava flows
volcanic glass
pyroclastic material
gaseous products

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

obsidian
pumice (vesicles0

volcanic glass if it is massive

Pumice (Vesicles)

A type of igneous rock that contains air bubbles

pyroclastic material

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

Gaseous products

H2O
CO2
SOs
H2S
CHI
H2S - egg smell

factors influencing explosively of magma

high gas content
high viscosity

resistance to flow

factors influence viscosity

chemical composition
temperature

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%
6 BOOM

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

very fluid
Shield volcanoes and cinder cones

Shield volcanoes

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)
Lava dome

Stratovolcanoes

a volcano built up of alternate layers of lava and ash.

Tabular intrusions known as dykes and sills

mushroom-like shape

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?

A) stratovolcano
B) caldera
C) shield volcano
D) cinder cone
E) dome

Eruptive Volcanic Hazards

Lava flows
pyroclastic material (tephra)
Pyroclastic Flows
Lahar
Toxic Gases
Volcanic Landslides

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

Pyroclastic Flows

turbulent mixtures of hot gas and pyroclastic fragments that are emplace laterally from a volcanic vent

Lithic Fragments

Lithic Fragments

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.

lahar/debris flow

destructive mixtures of water, ash, rock fragments of all sizes

sector collapse

When a volcano becomes structurally unable to support its own mass, a large portion of the volcano can fail catastrophically.

Volocanic landslides

debris avalanche

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
C) lahar
D) lava dome
E) lava flows

Explain WHY:

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?
hazard map

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
a.

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