Lesson 4 Flashcards by Sydney Perry

What are the primary factors of magma that determine the nature/violence of volcanic eruptions?

temperature
composition
amount of dissolved gas

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What is viscosity?

A measure of a materials resistance to flow

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As viscosity increases, the mobility _____.

decreases

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What are the factors that affect viscosity?

temperature
composition
volatiles (dissolved gasses)

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If the temperature of the magma is hotter, then it is _____ viscous.

less

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If the magma’s composition has a high silica content, the magma will have a _____ viscosity.

high

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If the magma’s composition has a low silica content, the magma will have a _____ viscosity because it has more ___..

low

fluid

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What is an example of a magma composition with a high silica content?

rhyolitic lava

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What is an example of a magma composition with a low silica content?

basaltic lava

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What is the most abundant volatile or gas in magma?

water vapor

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What are the main gasses in magma?

water vapor

carbon dioxide

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What provides the force to extrude lava?

gases expanding near the surface

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What is the violence of a eruption related to?

how easy gas escapes form magma

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When gases have a hard time to escape, they have a ____silica content, ____viscosity, and _____eruptions

high
high
violent

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What is congealing?

solidify by cooling

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When gases have an easy escape, they have a ____silica content, ____viscosity, and _____eruptions

low
low
non-violent

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What are the materials associated with volcanic eruptions?

lava flows
gases
pyroclastic materials

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Are basaltic lavas more or less fluid?

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What are the types of basaltic lava?

Pahoehoe lava

Aa lava

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What does Pahoehoe lava look like?

resembles braids in ropes

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What does Aa lava look like?

rough, jagged blocks

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Pahoehoe lava is _____ viscous than AA lava.

less

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What kind of flows does rhyolitic lava create?

short and thick flows

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What kind of flows does basaltic lava create?

fluid flows that travel long before congealing

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How much percent of magma by weight is gases?

1-5

What are pyroclastic materials also called?

"fire fragments"

What are the types of pyroclastic materials?

Ash and dust Pumice Lapalli Cinders

Give a description of ash and dust (pyroclastic material).

fine, glassy fragments

Give a description of pumice (pyroclastic material).

from "frothy" lava

Give a description of lapilli (pyroclastic material).

"walnut" size

Give a description of Cinders (pyroclastic material).

"pea-sized"

What are particles larger than lapilli?

blocks | bombs

What are blocks?

hardened lava

What are bombs?

ejected as hot lava

What is pulverized rock and lava fragments blown from the volcanos vent?

pyroclastic material

Successive eruptions of lava from a central vent results in a montainous accumulation of material called a ____

volcano

What is a volcanoes surface opening called?

vent

What is a steep-walled depression located at the summit called?

crater

The vent is connected to the ______ through a pipe.

magma chamber

What is the pipe that carries gas rich magma to the surface?

conduit

What is a caldera?

a crater that is greater than 1 km diameter

What is the cone shaped material formed from volcanic material not part of the central vet of a volcano.

Parasitic cones

What is the opening called where gases emerge?

fumaroles

What are the three types of volcanos?

shield cinder composite

What is a shield cone volcano shape?

broad, slightly domed

What are shield cones primarily built of?

fluid- basaltic lava

Shield volcanoes are generally sized ____ and produce a _____ of lava

large | large volume

What is an example of a shield volcano?

Mauna Loa in Hawaii

What type of volcano frequently occurs in groups?

Cinder cones

What is the shape of cinder cone volcanoes?

very steep slopes and rather small

What are cinder cones composed of?

pyroclastic material- ejected lava fragments

What are composite cones built of ?

interbedded lavas | pyroclastic deposits.

Where are most composite cones located?

adjacent to the pacific ocean

What is an example of a composite cone volcano?

Mt Rainer

What is another name for composite cones?

stratovolcanoes

What is the shape of composite cones?

large | nearly symmetrical

What volcano has the most violent type of activity?

composite cone

What do composite volcanoes often produce?

nuea ardente

What is a nuea ardente?

fiery cloud of hot gases infused with incandescent ash

Nuea ardente flows down the side of a volcano at speeds up to ____per hour?

200km (125 miles) per hour

Composite cones may generate mudflow called _____.

lahar

What is lahar?

a type of mudflow

What are most volcanoes are fed by?

conduits or pipes

What are resistant vents left standing after erosion has removed the volcanic cone?

volcanic neck

Volcanic eruptions from a central vent are the most familiar, but the largest amounts of volcanic material are extruded from ______

fissures

The term flood basalts describes the fluid, waterline, basaltic lava flows that cover an extensive region in the northwestern United States known as the __________

Columbia Plateau

When silica-rich magma is extruded, pyroclastic flows consisting largely of _______ fragments.

ash and pumice

How are calderas formed?

by collapse

What is the shape of calderas?

nearly circular

What is fluid basaltic lava extruded from crustal fractures?

fissures

What are short conduits that connect a magma chamber to the surface?

pipes

Example of a volcanic pipe and neck?

Ship Rock, New Mexico

Magma is created from a rock located where?

crust and upper mantle

How can a rocks temperature raise?

from hot mantle plume "ponds" beneath crustal rocks

What can happen when there is a decrease in pressure?

decompression melting

What can volatiles (water) do to a rock to generate magma?

lower a rock's melting point

What end of the compositional spectrum is the partial melting magma

granitic (felsic) end

What factors influence the generation of magma from solid rock

heat pressure volatiles partial melting

Earth's natural temperature increases with depth is called a ______

geothermal gradient

What three ways is heat created to melt magma?

Friction in subduction zones Crustal rocks heated during subduction Rising, hot mantle rocks

What happens to the temperature if the confining pressure increases?

melting temp increases

What plays an important role in subducting ocean plates?

volatiles

What kind of minerals is partial melting made of?

lowest-melting-temperature minerals

What is different from the low melting temp minerals and original rock?

they have a high silica content

What are most active volcanoes are associated with?

plate boundaries

Plate boundry found along mid-ocean ridges where seafloor spreading is occurring?

divergent plate boundaries

Rising plumes of hot mantle rock are the source of most ______

intraplate volcanism

what are the three plate motions providing help to create magma?

Convergent Divergent intraplate igneous activity

Name the plate motion. 1. Deep-ocean trenches are generated 2. Descending plate partially melts 3. Magma slowly rises upward forming a structure

convergent plate boundaries

What two structures can form from convergent plate boundaries?

Volcanic island arcs in an ocean | Continental volcanic arcs

What is the composition of Volcanic island arcs in an ocean?

Basaltic composition

What is the composition of Continental volcanic arcs?

Andesitic or rhyolitic composition

What is an example of a volcanic island arc in an ocean?

the Aleutians

What is an example of continental volcanic arcs?

Andes mountains

Name the plate motion. a. Activity within a rigid plate b. Plumes of hot mantle material rise c. Form localized volcanic regions called hot spots

Intraplate igneous activity

Where is the greatest volume of volcanic rock produced along

the oceanic ridge system

Name the plate motion. 1. Lithosphere pulls apart 2. Less pressure on underlying rocks 3. Partial melting occurs 4. Large quantities of fluid basaltic magma are produced

Divergent plate boundaries

Plate boundary in the vicinity of ocean trenches where one plate is being subducted beneath another?

convergent plate boundaries

Plate boundary in the interiors of plates themselves?

intraplate volcanism