Geology exam #1 Flash Cards

 
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What is a fissure eruption? Give examples of active volcanism and ancient volcanism through fissure eruption It is the most voluminous volcanic activity. The eruption of magma out of a crack in the lithosphere, rather than from a single pipe or vent.
It is generally harmless mafic (basalt)
It creates seafloor spreading ridges
In the formation of a fissure eruption highly fluid basalt erupting from fissures and then it forms widespread layers rather than mountains
Examples are the Colombia Plateau, India, and Brazil
0 stageka Thu, 11 Feb 2010 23:32:44 GMT view revision history
How is the present earth different from the primitive earth that formed about 4.6 billion years ago? Since then the universe has expanded to form the galaxies stars and planets

One of the planets, earth, gave rise to complex life forms. Over time, a tremendous diversity of life forms and ecological systems developed while the planet evolved and changed its interior churning, its landmasses shifting, and its surface constantly being reshaped.
Humans have learned to use not only planet & animal resources but also minerals, fuels, and other geologic materials.
0 stageka Thu, 11 Feb 2010 23:30:13 GMT view revision history
Why have 20th century earthquakes in Turkey suggested that some earthquakes begt subsequent earthquakes? Earthquakes have occured in a pattern from east to west 0 stageka Thu, 11 Feb 2010 23:30:13 GMT view revision history
Tsunamis travel More slowly in shallow water than in deep water, causing wave crests to rise 0 stageka Thu, 11 Feb 2010 23:30:13 GMT view revision history
Ground rupture occurs during an earthquake as A near surface fault breaks the surface 0 stageka Thu, 11 Feb 2010 23:30:13 GMT view revision history
Surface waves are produced by P waves and S waves reaching the surface 0 stageka Thu, 11 Feb 2010 23:23:35 GMT view revision history
On what basis are mercalli intensity values assigned to locations qualitative perceptions of and structural response to the shaking 0 stageka Thu, 11 Feb 2010 23:23:35 GMT view revision history
Steam explosions 1. water vapor cloud
2. volcanic bomb
3. magma conduit
4. layers of lava & ash
5. stratum
6. water table
7. explosion
8. magma chamber
0 stageka Thu, 11 Feb 2010 23:23:35 GMT view revision history
Lahars -debris & mud flows
-indonesian term
-most serious secondary volcano
-from the collapse of volcanic slopes
-sudden melting of snowcaps & glaciers at the top of a volcano
-rapid downslope flow at the speed of 50 km/hr
-long flowing distance: tens of miles from the volcano
-trigger submarine avalanches and tsunamis
0 stageka Thu, 11 Feb 2010 23:23:35 GMT view revision history
Debris avalanche Landslide of rock and soil material caused by volcanic eruption 0 stageka Thu, 11 Feb 2010 23:18:43 GMT view revision history
Poisonous Gases -volcanic gases: h2o, co2, co, so2, h2s
-floating in air
-dissolved in water
-dangerous for health, plants & animals
-producing smog air, acid rain, & toxic soil
-health effects of vog: breathing problems, head aches, sore throat, watery eyes
-can release from a dormant volcano
0 stageka Thu, 11 Feb 2010 23:18:43 GMT view revision history
Pyroclastic -enormous amount of rock fragments, volcanic glass fragments & bombs
-associated with explosive volcanic eruptions
-ash fall, from a more vertical ash eruption
-more deadly is a lateral blast
-covering large area
-wider impact if ash flows reach upper atmosphere
-harm to human health & structures
-hazardous for air traffic
-pyroclastic hot avalanches
0 stageka Thu, 11 Feb 2010 23:18:43 GMT view revision history
Calderas Result when a violent eruption empties a volcano's magma chamber, which then cannot support the overlying rock. It collapses, leaving a large, steep-walled basin 0 stageka Thu, 11 Feb 2010 23:18:43 GMT view revision history
Craters Found at the summits of most volcanoes. After an eruption, lava often sinks back into the vent & solidifies, to be blasted out by later pyroclastic explosion 0 stageka Thu, 11 Feb 2010 23:14:03 GMT view revision history
Stratovolcanoes (composite) -built up of layers of lava & pyroclastics
-mix of lavas & pyroclastics layers allow for a tall volcano to form
-usually associated with subduction zones
-violent and explosive
-built up from alternating layers of pyroclastic material & lava flows. lava that has solidified in fissures forms riblike dikes that strengthen the cone.
-ex. mount st. helens, cascade range, northwest us
0 stageka Thu, 11 Feb 2010 23:14:03 GMT view revision history
Cinder cones -minor explosive volcano
-batches of lava into the air as pyroclastics
-size of pyroclastics range from ash (very fine), cinders, bombs, or blocks (very coarse)
-pyroclastics fall close to the vent creating a cone shaped volcano
-formed when ejected material is deposited as layers that dip away from the crater at the summit. The vent beneath the crater is filled with fragmental debris
-ex. particutin, mexico
0 stageka Thu, 11 Feb 2010 23:14:03 GMT view revision history
Volcanic Domes -composed of more viscous andesite or rhyolite (do not flow)
-ooze out onto surface from a tube and pile up close to the vent
-compact, small, & steep sided
-various locations around pacific ring of fire
0 stageka Thu, 11 Feb 2010 23:14:03 GMT view revision history
Shield volcanoes -very large, flat, with abundant thin basalt flows
-basalt is less viscous than andesite or rhyolite
-shield like shape-larger area relative to height
-built up by the accumulation of thousands of thin basaltic flows that spread as gently sloping sheets. Magma can erupt on the flanks of a volcano as well as from the central vent
-ex. hawaii island chain
1 stageka Thu, 11 Feb 2010 23:09:05 GMT view revision history
Magma Formation Increases temperature, decrease pressure, & add water
Magma sources come from the crust & upper mantle and then melted
Composition is dictated by source material and partial melting
Mineralology is the composition
Volcanic eruption style depends on lava's viscosity and amount dissolved
and viscosity is determined by lava composition
0 stageka Thu, 11 Feb 2010 23:08:47 GMT view revision history
what determines the rock melting temperature of magma Temperature increases with depth
In the upper mantle the temp. is high enough & the pressure low enough to have melt at certain plate tectonic settings
The composition is dictated by the plate tectonic setting & the extent of melting
0 stageka Thu, 11 Feb 2010 23:08:47 GMT view revision history
Viscosity Liquid's resistance to flow
Determined by silica content (lava composition)
0 stageka Thu, 11 Feb 2010 23:08:47 GMT view revision history
Magmas at hot spots -will produce a basalt lava
-under oceanic crust generally will produce a felsic lava (& explosive)
0 stageka Thu, 11 Feb 2010 22:59:01 GMT view revision history
Magma at convergent plate boundaries -complex
-the composition of the subducted plate determines the composition of the lava
-subducted continental crust may melt and produce rhyolite lava
-oceanic crust may melt & produce andesite or basalt lava
-from the top may melt & produce a variety of lavas
0 stageka Thu, 11 Feb 2010 22:59:01 GMT view revision history
Magma at divergent plate boundaries -typically melted asthenosphere material
-extremely rich in ferromagnesium (ultramafic) and a melt from it is mafic
-basalt is places as new seafloor at the spreading of rift or ridge
0 stageka Thu, 11 Feb 2010 22:59:01 GMT view revision history
Intermediate Magma Intermediate viscosity
produce andesite
combination of lava flows & explosive activity
0 stageka Thu, 11 Feb 2010 22:59:01 GMT view revision history
Felsic Magma -High SiO2
-thick, high viscosity, does not flow easily
-Gas trapped bc the magma is stiff
-more explosive
-pyroclastic material
-rhyolite
1 stageka Thu, 11 Feb 2010 22:54:30 GMT view revision history
Mafic Magma -High in Fe and Mg
-Thin, low viscosity magma, flows easily out of the vent
-Gas escapes because the magma flows easily
-Less explosive
-Mostly lava
-basalt
1 stageka Thu, 11 Feb 2010 22:54:21 GMT view revision history
Surface wave motion 1. Ripple across earth's surface, where air above the surface allows free movement
2. Two types:
- Rayleigh waves - ground moves in a rolling, elliptical motion that dies down with depth beneath the surface
- Love waves - Ground shakes sideways with no vertical motion
0 stageka Thu, 11 Feb 2010 22:52:49 GMT view revision history
S wave motion 1. S waves (secondary) travel at about 1/2 the speed of P waves
2. Shear waves that push material at right angles to their path of travel
0 stageka Thu, 11 Feb 2010 22:52:49 GMT view revision history
P wave Motion 1. P waves (primary) are compressional waves, like sound waves, that travel quickly through rock
2. Travel as a series of contractions & expansions, pushing & pulling particles in the direction of their path of travel
0 stageka Thu, 11 Feb 2010 22:48:45 GMT view revision history
Seismic Waves -Propagate outward from the focus
-Body wave: travels through the interior of the earth
-P wave: compressional waves, travel fastest through all physical states of media
-S wave: shear wave, travel slower than p waves
-Surface wave: moving along the earth's surface travel slowest but cause the most damage
-Primary, secondary, & surface waves travel at different speeds & arrive at the seismograph at different times
0 stageka Thu, 11 Feb 2010 22:48:45 GMT view revision history
Material Amplification Seismic waves travel differently through different rock materials
Propogate faster through dense & solid rock
It is the intensity of ground shaking more severe in unconsolidated materials
Seismic energy attenuated more & propagated less distance in unconsolidated materials
Hard rock- low amplitude shaking
Silt, mud- high amplitude shaking
0 stageka Thu, 11 Feb 2010 22:48:45 GMT view revision history
Rupture and Damage of Earthquakes Primary Effects: ground shaking, tilting, & ground rupture. Loss of life & collapse of infrastructure

Secondary Effects: landslides, liquefaction, & tsunamis. Fires, floods & diseases

Tertiary Effects: Social & psychological impacts

Ground Motion: surface waves produce most damage
0 stageka Thu, 11 Feb 2010 22:48:45 GMT view revision history
Convergent Plate Boundary Wide zone of shallow, intermediate, & deep earthquakes.
80% of seismic energy released along the earthquake zone around the pacific rim

Deep ocean trench
0 stageka Thu, 11 Feb 2010 22:40:02 GMT view revision history
Transform Plate Boundary Shallow to intermediate earthquakes 0 stageka Thu, 11 Feb 2010 22:40:02 GMT view revision history
Divergent Plate Boundary Shallow earthquakes

Mid ocean Ridge
Rift Valley
Normal Fault
lateral shearing
0 stageka Thu, 11 Feb 2010 22:40:02 GMT view revision history
Mercalli Scale -12 divisions
-Qualitative severity measurement of damages and ground movement
-Based on ground observations, instead of instrument measurement
-Scale depending on earthquake's magnitude, duration, distance from the epicenter, site geological conditions & condition of infrastructure
0 stageka Thu, 11 Feb 2010 22:40:02 GMT view revision history
Richter Scale The amplitude of ground motion
Increasing one order in magnitude, a tenfold increase in amplitude

Movement Magnitude Scale
Measuring the amount of strain energy released
Based on the amount of fault displacement
Applicable over a wider range of ground motions than the richter scale
0 stageka Thu, 11 Feb 2010 22:36:32 GMT view revision history
How are earthquakes measured and Located? Seismographs: machines that record the seismic waves generated by earthquakes (vertical and horizontal ground movements)
Locate by the epicenter
Seismic waves from an earthquake move out from the focus & arrive at distant seismographic stations at diff. times
The graph of the travel time vs. distance is called a travel time curve bc P waves are almost twice as fast as S waves and the interval btw their travel time curves increases with distance
By matching the observed interval to the spacing of the curves, a geologist can determine the distance from the station to the epicenter. An 8 min. interval occurs at about 5600 km from the epicenter
If the geologist then draws a circle with a radius calculated from the travel time curves around each seismographic station the point at which the circles intersect will locate the earthquake's epicenter
0 stageka Thu, 11 Feb 2010 22:36:32 GMT view revision history
Earthquakes Earthquakes represent a release of built up stress in the lithosphere.
When the stress exceeds the rupture strength of a rock a sudden movement occurs to release the stress.
With the sudden displacement & associated stress release, the rocks snap back elastically to their previous dimensions which is called elastic rebound.
Occur along linear belts & most are within a plate, or some are between plates.
0 stageka Thu, 11 Feb 2010 22:36:32 GMT view revision history
Faults -Actual site of movement along a fault is the focus
-Actual point on the earth's surface above the focus is the epicenter
-Normal: occur at divergent plate boundaries
-Reverse: occur at convergent plate boundaries
-Strike-Slip: occur at transform plate boundaries
-creep aseismic slip is gradual movement along a fault and in an earthquake it occurs where new rocks being stressed suddenly break along a new or pre-existing fault.
0 stageka Thu, 11 Feb 2010 22:36:32 GMT view revision history
How does Deformation relate to the earthquake cycle and elastic rebound theory? -energy releases from a dynamic earth occur along faults
-Earth's crust moves very slowly and overtime enough stress builds up and a brittle release occrus- an earthquake
-Stress is released and transfered (elastic rebound theory)
0 stageka Thu, 11 Feb 2010 22:19:17 GMT view revision history
Elastic Deformation Temporary strain, object recovers original size and shape once the stress is removed.
Elastic limit: Strain that becomes permanent in an object once limit of recoverable strain has been exceeded
Plastic Deformation: occurs in materials once elastic limit has been exceeded
Brittle Deformation: occurs at the limit of strength of the material, a rupture of a break occurs
0 stageka Thu, 11 Feb 2010 22:19:17 GMT view revision history
Strain-Deformation
Rock response to plate tectonics
.Stress-force applied on a rock
-compressive stress: squeeze or compress an object
-tensile stress: pull or stretch an object
-shearing stress: different parts of an object move in different directions or at different rates
.Strain- temporary or permanent.
0 stageka Thu, 11 Feb 2010 22:19:17 GMT view revision history
Wegener's Theory of Continental drift and modern plate tectonic theory Continental drift turned out to be just one aspect of a broader theory known as plate tectonics
Tectonics is the study of large scale movement and deformation of the earth's outer layers.
Plate tectonics relates such deformation to the existence and movement of rigid "plates" over a weak or partly molten later in the earth's upper mantle
0 stageka Thu, 11 Feb 2010 22:19:17 GMT view revision history
Subduction Zone. How fast do plates move? d/t
velocity= 60km/3.3mil. year=18km/mil.yr.
0 stageka Thu, 11 Feb 2010 21:44:34 GMT view revision history
Transform-fault boundaries a. mid ocean ridge transform fault
-lateral (transform) faults & earthquakes
-north american plate: eurasian plate
b. continental fault boundaries
-lateral (transform) faults & earthquakes
- pacific plate-north american plate
1. as the pacific plate & north american plate move past each other in opposite directions, creek beds crossing the fault have been off set
0 stageka Thu, 11 Feb 2010 21:44:34 GMT view revision history
Convergent Boundaries a. ocean-ocean convergence
-oceanic trench, volcanic island arc, & deep earthquakes
-philippine plate-pacific plate: mariona islands-mariona trench
b. ocean continent convergence
-volcanic mountain chain, folded mountains, & deep earthquakes
-nazca plate-south american plate: peru-chile trench-andes mountains
c. continent-continent convergence
-himalayan mountains, crustal thickening, folded mountains, & earthquakes, tibetan plateau, subduction
-indian australian plate-eurasia plate
0 stageka Thu, 11 Feb 2010 21:38:31 GMT view revision history
Divergent Boundaries a. oceanic plate separation
-rifting, volcanoes, and earthquakes
-north american plate-eurasian plate: mid atlantic ridge
b. continental plate separation
-rift valleys, volcanoes and earthquakes
- african plate-somali subplate: eastern rift valley
0 stageka Thu, 11 Feb 2010 21:38:31 GMT view revision history
The driving force behind plate tectonics Mantle Convection System
-spreading centers & hot spots
-convection causes hot water to rise
-where it cools, moves laterally, sinks
-warms & rises again
-hot matter from the mantle rises
-causing plates to form and diverge
-where plates converge, a cool plate is dragged under
-sinks warms and rises again
2 stageka Thu, 11 Feb 2010 21:43:38 GMT view revision history
Cross Section of the earth Crust
Mantle (less dense continental crust floats on denser mantle. continental crust is less dense on oceanic crust)
Liquid iron outer core
solid iron inner core
0 stageka Thu, 11 Feb 2010 21:38:31 GMT view revision history
Geologic Time Deep Time
me= 20 years old
oldest rocks= 4000 million yrs. ago
earth= 600 million yrs. old
how old was earth percentage?

600m/4600m=.13=13%
i was .13 x 20 = 2.6 yrs. old when same % of my life had passed

most of the major geologic events have occurred in the relative recent past, compared to the full earth history
0 stageka Thu, 11 Feb 2010 21:20:36 GMT view revision history
Bombardment from space collisions with medium to large asteroids were common in the early history of the solar system
some significant impacts have occurred throughout earth's history including one 65 million years ago caused a mass extinction of life on earth including the dinosaurs
0 stageka Thu, 11 Feb 2010 21:20:36 GMT view revision history
Chemical Differentiation Continents: Cooked & solidified magma that floated up from the mantle
Oceans & atmosphere: fluid outer layer derived from volatile transfer of gases from the interior
0 stageka Thu, 11 Feb 2010 21:20:36 GMT view revision history
The core Gravitational energy--heat
about 100-200 million years after initial accretion temps at depths of 400-800 km below the earth's surface reach the melting point of iron
iron melts and pulled to the center of the core
0 stageka Thu, 11 Feb 2010 21:20:36 GMT view revision history
The Nebular Hypothesis -a large gas cloud (nebula) begins to condense
-most of the mass is in the center, there is turbulence in the outer parts.
-turbulent eddies collect matter measuring meters across. Small chunks grow & collide, eventually becoming large aggregates of gas & solid chunks
-a diffuse, slowly rotating nebula begins to contract
-a flat rapidly rotating disk forms with the matter concentrated of the center that will become the proto-sun
-disk of gas forms grains that collide & clump together into planetesimals
-terrestrial planets build up by multiple collisions & accretion of planetesimals by gravitational attraction. Giant outer planets grew by gas accretion
0 stageka Thu, 11 Feb 2010 18:33:36 GMT view revision history
Theory versus Hypothesis Theory-accepted explanation

-must be a well tested model
-is subject of considerable investigation and data collection that is required to evaluate it
-a hypothesis is elevated to a theory only after extensive debate & experimentation
0 stageka Thu, 11 Feb 2010 18:33:36 GMT view revision history
Steps in the Scientific Method
Hypothesis & Theory
Hypothesis is formed to explain the observations or data.
-Conceptual framework or model is developed
-Multiple explanations or equations developed
-Must be testable and test must be reproducible
-Proof of a hypothesis is sought as well as evidence to disprove it

Test the hypothesis repeatedly & systematically

-Make set of predictions & perform series of experiments

Theory formed as accepted explanation for an observation or set of data

- hypothesis becomes a theory only after extensive testing of the hypothesis
0 stageka Thu, 11 Feb 2010 18:33:36 GMT view revision history

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