Earth Science Exam 3

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3 Intrusive Volcano Types

Back 1

Sheild, Composite, Cinder Cone

Front 2

3 factors that determine violence of eruption

Back 2

composition of magma (silica content)

temperature of magma

gases dissolved in magma (and how easily they can escape)

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Viscosity

Back 3

- a measure of a material's resistance to flow

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3 Factors affecting viscosity

Back 4

Composition (silica content)
-High silica – high viscosity
-Low silica – more fluid (e.g., basaltic lava)

Temperature (hotter magmas are less viscous)

Dissolved gases (volatiles) *Mainly water vapor and carbon dioxide Gases expand near the surface

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Dissolved gases (volatiles) -

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Provide the force to extrude lava

Depends on how easily gas can escape
- Easy escape from fluid magma
-Viscous magma produces a more violent eruption

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2 types of lava flow

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Pahoehoe (hotter and flows easier; less viscous)

Aa- rough, jagged rocks. hardened pieces of solidified magma

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Pyroclastic materials

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Ash and dust – fine, glassy fragments

Pumice – from "frothy" lava

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Conduit,

Back 8

or pipe caries gas-rich magma to the
surface

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Vent

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the surface opening (connected to the
magma chamber via a pipe)

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Crater

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Steep-walled depression at the
summit

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Caldera

Back 11

(a summit depression
greater than 1 km diameter)

Steep walled depression at the summit Formed by collapse, Nearly circular

EX:Crater Lake, Oregon, AND on mars @ mt olympus

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Shield Volcano

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Broad, slightly domed Primarily made of basaltic (fluid) lava
Generally very large size

Mauna Loa in Hawii

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Composite Volcano

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(or stratovolcano) Large size, Inter-bedded lavas and pyroclastics, Most violent type of activity

usually at oceanic and continental convergent boundaries

granite and viscous

mt. st. helens and cascades

make Nuée Ardente

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Nuée Ardente

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Fiery pyroclastic flow made of hot gases infused
with ash •

Flows down sides of a volcano at speeds up to 125 miles per hour

can produce lahar

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lahar

Back 15

volcanic mudflow

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cinder cone volcano

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Built from ejected lava fragments
Steep slope, smaller size, frequently occur in groups

ex: sunset crater, arizona

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Fissure eruptions and lava plateaus

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Fluid basaltic lava extruded from crustal fractures called fissures

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magma

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“Lava” within interior

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pluton

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Pluton - an underground igneous body

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plutons are classified by

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Classified by:
• Shape - Tabular (sheetlike), Massive

Orientation with respect to the host (surrounding) rock

Discordant – cuts across existing structures
Concordant – parallel to features such as sedimentary strata

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4 Types of Igneous Intrusive Features

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Dike- tabular, discordant pluton

sill- tabular, cordant pluton

Laccolith – Lens shaped mass (Similar to a sill) concordant, Arches overlying strata upward

4. Batholith – Largest intrusive body, Frequently form the cores of mountains

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4 Factors that influence the generation of magma from rock

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Heat - Geothermal Gradient -not sufficient to melt all
rock

2. Pressure increase in melting temperature
-Drop in confining pressure can cause decompression melting
-Lowers the melting temperature Occurs when rock ascends

3. Volatiles • Primarily water
Origin of magma cont.
Cause rock to melt at a lower temperature Play an important role in subducting ocean
plates
4. Partial melting Igneous rocks are mixtures of minerals
-Melting occurs over a range of temperatures
-Produces a magma with a higher silica content than the original rock

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Where igneous activity occurs

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Most volcanoes are located on the margins of the ocean basins

Second group is confined to the deep ocean basins (basaltic lavas)

Third group includes those found in the interiors of continents

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Rising magma can form...

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-Volcanic island arcs in an ocean
(Aleutian Islands)
-Continental volcanic arcs (Andes Mountains)

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earthquakes

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Vibration produced by the rapid release of energy

vibrations (earthquakes) occur as rock elastically returns to its original shape

Often preceded by foreshocks and followed by aftershocks

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Elastic Rebound

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pre-earthquake:

1. potential energy is stalled

2. builds up until there is enough force to break free.

3. finally moves, and energy is release and send out!

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seismology

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• Study of earthquake waves is called seismology

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2 types of earthquake waves

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1. Body waves
a. Primary (P) waves –
b. Secondary (S) waves –

2. Surface waves -

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Primary (P) waves –

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Push-pull (compressional) motion; Can travel through solids, liquids, and gases

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Secondary (S) waves –

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"Shake" motion; Travels only through solids

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Surface waves -

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Complex circular motion; Slowest; most destructive wave

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Focus

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Focus – the place within Earth where earthquake waves originate

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Epicenter -

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Point on the surface, directly above the focus

Located using the difference in the arrival times between P and S wave recordings, which are related to distance

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triangulation

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used to determine location of epicenter

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Shadow Zone

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- Absence of S waves from about 105 degrees to 140 degrees around the globe from an earthquake

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Magnitude

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– Based on amplitude of largest seismic wave

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Intensity –

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(Mercalli Scale) based on damage sustained

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Factors that determine structural damage

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1. Intensity of the earthquake
2. Duration of the vibrations
3. Nature of the material upon which the
structure rests
4. The design of the structure

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Destructive things caused by earthquales

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Liquefaction – saturation of ground material turning into a fluid

landslide

fire

tsunami

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Earthquake Prediction

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Short-range – No reliable method yet devised for short-range prediction

Long-range –Earthquakes are repetitive; Region is given a probability of a quake

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Earth Layers defined 2 ways;

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Composition and Physical Characteristics

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Composition

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Composition – Chemical makeup of rocks; Layers
include:
1. Crust –

2 Types Thin, rocky outer layer
Varies in thickness;

Roughly 5 miles in Oceanic regions;
Roughly 25 miles for Continental crust (Exceeds 40 miles in some
mountainous regions!)

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crust

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1. Crust –

2 Types Thin, rocky outer layer

Oceanic Crust; Basaltic composition (<180 myo);

Continental crust: Granitic composition; (~4 byo)

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Mantle: Peridotite (Speculative) Evidence:

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Mantle: Peridotite (Speculative) Evidence:
• Lava from the asthenosphere has a composition similar to that which results from the partial melting of
peridotite (depths to ~1,800 mi)

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Core: Iron-nickel alloy Evidence:

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Core: Iron-nickel alloy Evidence:
• physical characteristics and Meteorites (Depths to ~2,161 miles)

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Physical Characteristics

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1. Lithosphere: Cool, rigid, solid;
includes the Crust and uppermost mantle (~62 mi thick)
2. Asthenosphere: Soft, Weak; Beneath the lithosphere but still in the Upper
mantle; easily deformed (depths to ~412 mi)

3. Mesosphere: more rigid but rocks (or lower mantle) are hot and capable of gradual flow

4. Outer Core: Liquid; convection generates Earth’s magnetic field

5. Inner Core – Solid;

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Lithosphere:

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Lithosphere: Cool, rigid, solid;
includes the Crust and uppermost mantle

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Asthenosphere:

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Asthenosphere: Soft, Weak; Beneath the lithosphere but still in the Upper
mantle; easily deformed

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Mesosphere:

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Mesosphere: more rigid but rocks (or lower mantle) are hot and capable of gradual flow

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Outer Core:

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Liquid; convection generates Earth’s magnetic field

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5. Inner Core –

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Solid;