Geol 101 - Ch. 4 Up from the Inferno: Magma and Igneous Rocks

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What is a volcano?

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46 Terms

1

What is a volcano?

A vent or opening from which melt that originates inside the Earth emerges onto the planet’s surfaces.

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2

What is magma?

Underground melt; molten rock beneath the Earth’s surface.

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3

What is lava?

Emerged melt'; molten rock that has flowed out onto Earth’s surface.

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4

What is extrusive igneous rock?

Forms when lava that freezes above ground comes into contact with air/water after it erupts.

<p>Forms when lava that freezes above ground comes into contact with air/water after it erupts. </p>
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5

What is pyroclastic debris?

Fragmented material that sprayed out of a volcano and landed on the ground/seafloor in solid form.

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6

What is volcanic ash?

Tiny glass shards from lava sprays.

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7

What is intrusive igneous rock?

Rock formed by the freezing of magma underground; solidification of magma.

<p>Rock formed by the freezing of magma underground; solidification of magma. </p>
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8

What are causes of melting?

  1. Decompression

  2. Addition of Volatiles

  3. Heat Transfer

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9

What is decompression?

Decrease in pressure triggers melting as long as temperature stays the same.

<p>Decrease in pressure triggers melting as long as temperature stays the same. </p>
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10

What is the addition of volatiles?

Substances that evaporate really easily; decreases a rock’s melting temperature.

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11

What is melting due to heat transfer?

Hot magma from the mantle rises into the crust and it’s heat raises the temperature of surrounding crustal rock.

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12

What do all molten rocks include?

Silica (SiO2)

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13

What are dry melts?

They do not contain volatiles.

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14

What are wet melts?

They contain volatiles.

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15

Mafic Melts

Contain a relatively high proportion of magnesium oxide/iron oxide with silica

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16

Ultramafic Melts

An even higher proportion of magnesium oxide and iron oxide.

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17

Intermediate Melts

Composition between the mafic and felsic melts.

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18

Source-rock Composition

Reflects the composition of the solid from which it was derived.

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19

Partial Melting

Lowest temperature materials melt while higher temperature remain solid.

<p>Lowest temperature materials melt while higher temperature remain solid. </p>
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20

Assimilation

The incorporation of chemicals that dissolved from the wall rock/from blocks that detached from the wall and sank into magma.

<p>The incorporation of chemicals that dissolved from the wall rock/from blocks that detached from the wall and sank into magma. </p>
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21

Magma Mixing

Formed in different locations from different sources that may come into contact underground.

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22

Why does magma rise?

  1. Buoyancy

  2. Magma Pressure

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23

What controls the speed of magma flow?

Viscosity; The resistance of material to flow

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24

Which is more viscous?

A dry melt is more viscous than a wet melt.

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25

What are the three factors the cooling time of magma?

  1. Depth of intrusion

  2. The shape and size of a magma body

  3. The presence of circulating groundwater.

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26

What is fractional crystallization?

The process by which a magma becomes progressively more silicic as it cools, because early-formed crystals settle out.

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27

What is a magma chamber?

A space below ground filled with magma; does not contain melt, rather a “mush”

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28

Extrusive Igneous Settings

When this lava freezes; it forms a thin lava flow which takes days-months to cool.

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29

Intrusive Igneous Settings

Roughly planar and have a fairly uniform thickness; forms when magma injects into cracks underground.

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30

What is a dike?

A tabular intrusion that cuts across pre-existing layering.

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31

What is a sill?

A tabular intrusion that injects between layers; parallel

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32

Laccolith

A blister-shaped igneous intrusion that forms when magma injects between layers underground

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33

Plutons

Blob-shaped intrusions that range in size from tens of meters to tens of kilometers across; form when magma in a magma chamber solidifies.

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34

Batholith

Resulting immense mass of igneous rock

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35

Where do dike intrusions exist?

In regions where the crust stretches horizontally happens in a rift; magma forces it way a vertical crack → walls of crack move apart sideways.

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36

How is the space of plutons developed?

Rose upward though the crust as light-bulb-shaped blobs of magma that pierced overlying rock and pushed it aside as they rose.

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37

Stoping

A process during which magma assimilates wall rock, and blocks of wall rock break off and sink into the magma.

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38

Xenolith

A relict of wall rock surrounded by intrusive rock when the intrusive rock freezes

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39
<p>What texture is this?</p>

What texture is this?

Crystalline Texture

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40
<p>What texture is this?</p>

What texture is this?

Fragmental Texture

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41
<p>What texture is this?</p>

What texture is this?

Glassy Igneous Rocks

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42

What are hot spots?

Igneous activity with mantle plumes rising from deep in the mantle.

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43

Volcanic Arc

Forms on the overriding plate adjacent to the deep-sea trenches that mark convergent boundaries.

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44

How does subduction trigger melting?

Volatiles are bonded to other elements within mineral crystals

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45

Large Igneous Province (LIP)

A region in which huge volumes of lava/ash erupted over a relatively short interval of geologic time.

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46

Flood Basalts

Vast sheets of basalt that spread from a volcanic vent over an extensive surface of land; formed by rifting above a continental hot spot.

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