Exam 3 Flashcards by Stephanie Eubank

All the geological processes that give rise to volcanoes and volcanic rock

Volcanism

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Landform created by the accumulation of lava and other erupted materials

Volcano

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Molten rock below the Earth’s crust

Magma

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Molten rock material on earth surface

Lava

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Texture of extrusive of igneous rock where some crystals are visible but enclosed in glass

Porphyritic

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Texture of extrusive igneous rock where holes in rock due to gas trapped inside solidifying lava

Vesicular

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Volcanic glass black with concoidal fracture

Obsidian

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Frothy volcanic glass very light

pumice

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A fluids resistance to flow

Viscosity

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Crumbly more rocky coal like looking basaltic magma

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Ropey smoother flowing basaltic magma with metallicy looking cooling “skin” on top

Pahoehoe

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Cone like structure formed at places of basaltic magma; pieces spatter up and make cone like structure

Spatter cone

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Place where basaltic lava flows and crystallizes on top creating a tube structure

Lava tubes

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Pillow like blocks of lava that form underwater (any body of water); rounded in shape

Pillow Lava

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Hexagonal pattern that is a cooling feature of basaltic lava (a.k.a. basaltic jointing)

Columnar jointing

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Rock fragment ejected into the air by volcanic eruption, classified by size

Pyroclast

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Hot and fast, mainly composed of Ash, steam, gases, and other pyroclastic material (very deadly)

Pyroclastic flow

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Broad, gently sloping

successive basaltic lava flows from a central vent

Shield volcano

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Form with in craters of composite volcanoes; steep sided; viscous, felsic lavas (rhyolite and andesite) squeeze out a central vent

Explosive eruption

Lava dome / volcanic dome

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Cone composed of pyroclastic fragments (versus lava) explosively ejected from a central vent; usually basaltic

Cinder cone (scoria)

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Alternating layers of lava and pyroclastic; usually andesitic composition

Strato volcano (composite)

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Large; steep walled, basin shaped depression formed by violent eruptions: large volumes of magma erupted
Example crater Lake and Yellowstone

Caldera

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Basaltic lava erupted through vertical fractions; not from a central vent (gentle eruption with lava fountains usually)

Fissure eruption

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Immense basaltic lava plateaus in flat, layered flows originating from fissure eruptions

Flood basalt

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Mudflows of wet volcanic debris. caused by many different things such as pyroclastic flows meeting water, breaking of crater lake walls, melting of glaciers ice, or heavy rain on new ash deposits

Lahars

Volcanoes formed by the build up of thousands of eruptive deposits are inherently unstable. Sides can become too steep and fail, sometimes catastrophically example Mount St. Helena

Flank collapse

One of most destructive natural phenomenon on earth a single abruption can release thousand times the amount of debris in 1980 St. Helens abruption Ash deposits can be up to 100 feet thick or more and can go super fun

Caldera collapse

Can be as got as 300 to 400°C and travel as fast as 60 mph Mainly composed of ash, steam, gases, and other pyroclastic materials example Pompeii most deadly

Pyroclastic flows

Can be deposited over thousands of square kilometers Vegetation destroyed, surface water can be contaminated 1 cm of ash can collapse roofs, even less if a mix of ash and water Can harm health and breathing

Volcanic ash

Composition is magic and has a low silica content and the viscosity is low and flows far and fast

Basaltic magma/lava

Intermediate composition, silica content, viscosity, and temperature; it's in the middle of the spectrum between basaltic and rhyolite

Andesitic lava

Composition is felsic, with a high silica content viscosity and gas content; is pinkish in color and has a lower temperature than basaltic Explosive eruption

Rhyolitic lava

Siliclastic sediment rocks are classified by________

Size of the individual particles

Which of the following is an example of a clastic sedimentary rock

Sand stone

Small particles weather faster than large particles because________

They have more surface area per volume on which chemical reactions can occur

An unconformity that is between two parallel sedimentary layers and can be particularly difficult to see

Disconformity

The intrusive equivalent of rhyolite is _____

Granite

Three things that effect viscosity

Temperature of lava, gas content, and composition

Violent motion of the ground that occurs when rocks being stressed suddenly break along a new or preexisting fault

Earthquake

Force that causes rocks to deform

Stress

How much a rock will bend or deform

Strain

Rocks will break when they're stressed beyond a critical value

Failure

Break in bed rock along which movement has taken place

Fault

Rocks either side of the fault of the deform by tectonic forces; remain locked in place by friction. Accumulate elastic strain until they fail and rebound to to their undeformed state

Elastic rebound theory

Average length of time between quakes calculated from plate movement rate, expected amount of fault slip

Reoccurrence interval

The recording of the seismic waves released from an earthquake; used to determine the intensity

Seismogram

A machine that measures and records seismic waves that quakes generate

Seismograph

The point at which energy is first released; the first point of failure

Focus

The point on the earth surface directly above the focus

Epicenter

Small earthquake that occur shortly before a main shock; rarely used to protect earthquakes; difficult to discern from background seismicity

Foreshock

An earthquake that occurs as a result of a main shock

Aftershock

Ground vibrations produced by quakes

Seismic waves

Push pull waves

P waves

Shearing waves

S waves

Travel through interior of Earth; spread from focus in all directions example P waves and S waves

Body waves

Travel on the surface of Earth; away from epicenter

Surface waves

Elliptical waves with vertical motion; most destructive wave type because more ground movement, takes longer to pass

Raleigh waves

Side to side movement, no vertical displacement; horizontal movement knocks down buildings, topples bridges

Love waves

Numerical scale measuring intensity of ground motion and energy released by the earthquake event

Richter scale

Objective measure based on physical properties of the fault: | Strength of rock, surface area of rupture, and amount of displacement

Moment magnitude scale

Measures intensity of shaking based on subjects observations: Visual observations and feelings of people who experienced the quake

Modified mercalli scale

Talk, fast-moving sea waves generated by an earthquake that occurs beneath the ocean

Tsunami

Expected intensity of seismic shaking and ground disruption at specific location

Seismic hazard

The temporary transformation of solid material to a fluid state caused by the pressure of water in the pores of the material

Liquefaction

Looking at history of quake activity along a fault. Absolute dating within a disturbed later. Reoccurrence intervals calculated

Paleoseismology

Distinct zone of earthquakes that begin at oceanic trenches, sloping at a steep angle

Benioff zone

Old fault and rift zones that were once part of ancient plate boundaries; zones of crustal weakness

Intraplate earthquakes

Four ways to reduce damage from earthquakes

Land-use policy, earthquake engineering, emergency preparedness and response, tsunami warnings

Five earthquake related hazards

Ground motion, landslides and ground failure, fires, aftershocks, and tsunamis

The downhill movement of large masses of soil/rock under the influence of gravity

Mass wasting

Slower side of rock unit down a plan of weakness; travels a shorter distance and not as fast

Rock slide

Large blocks attached info from a vertical face

Rockfall

Very fast flow of solid rock; turbulent movement; loses internal structure; has greater velocity

Rock avalanche

They slow down hill flow of soil, Low slope angles

Creep

Abundant rainfall turns soil into a flowing fluid that can quickly flow down slope

Earthflow

High rainfall amounts loosen permeable material (rock, mud, surface debris); flows faster than earth flows

Debris flow

Very fine particles, contains lots of water, very little resistance to flow; very fast moving; lahars on volcanoes

Mud flows

Mass of unconsolidated material slides short distance as a unit; leaves spoon shaped, curved detachment surface

Slump

Rock, soil, and Surface debris slide as several units on a plane of weakness

Debris slide

Unconsolidated; loses internal structure; turbulent; very fast because high air/water content; very quickly down steep slopes

Debris avalanche

Sediment laden water that travels down continental slope onto abyssal plain

Turbidity current

What triggers mass movements

Earthquake, volcanic eruption, loss of vegetation, heavy rain or snow melt, over steepening, human impact

How do you prevent mass wasting

Improving drainage, vegetation, lower slope angle, stabilize steep slopes

Exam 3 Flashcards

(83 cards)