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78 Cards in this Set
- Front
- Back
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What are some internal forces?
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Compression and heat, earthquakes
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What are some external forces?
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Weathering and erosion
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What are the sources for internal forces?
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The earth's core
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What are the sources for external heat?
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The sun
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What is an earthquake? Why does it occur?
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Seismic energy is released when stress builds up in rock. Energy propagates through rock until it reaches the surface and the ground shakes.
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Where can earthquakes happen?
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Anywhere where there is a fault
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What is a fracture?
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A break/crack in a rock
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Where do fractures occur?
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Anywhere where stress is building up insides of rocks.
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What is the focus?
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Where the earthquake actually occurs. The location of the earthquake
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What is the epicenter?
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On the surface, closest to the focus. Usually the strongest shaking.
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What type of information can we get from earthquakes?
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The composition of the interior of earth. We can learn about the history and formation of the earth
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Is it possible for earths quakes to occur here in Massachusetts?
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Yes, it is always a possibility
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What are seismic waves?
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The form in which earthquake energy is released.
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What is a fault scarp?
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A sharp edged ridge
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What is the San Andreas Fault?
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Parts of it behave differently, strike slip fault, located in California, one of the most studied faults.
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What are aftershocks?
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Small earthquakes that occur after a major earthquake
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Tensional Stress
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Rock being pulled apart
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Compressional Stress
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Rock being pushed together
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Shear Stress
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Rock grinding past each other
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What is the elastic rebound theory?
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It can only occur where rocks are somewhat flexible but brittle. Stress builds up, is released and rock ellastically rebounds back into place.
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Are size and timing of earthquakes predictable yet?
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No. However, we can make predictions based on statistical analysis of history of earthquakes.
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What are body waves?
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Energy released at the focus, site of rupture. (inside)
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What are p-waves?
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Body waves, primary waves, push-pull compression-extension motion, can travel through solids, liquids, and gases
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What are s-waves?
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Body waves, secondary waves, can only travel through solids, propagates like a wave at a baseball stadium
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What are surface waves?
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Secondary propagation as body waves reach the surface. Originate at the epicenter
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What are love waves?
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Surface waves, faster than Rayleigh waves, cause horizontal surface damage ( side to side motion)
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Rayleigh waves
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Surface waves, occurs on the surface the move in an elliptical motion, move the ground up and down, side to side, most shaking felt is due to this wave
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What is a seismograph?
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An instrument must have one part that does not move, they are digital now, measures seismic waves
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What is a seismogram?
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A record of ground movements
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What is the Ricter scale?
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Based on height of the largest seismic wave that was recorded on the seismograph. Only useful for small and shallow earthquakes.
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What is moment magnitued?
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Estimates energy released by the earthquake, the amount of displacement that occurs along the fault
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What is the Mercalli scale?
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Rates earthquakes intensity and it's affects on different locations
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What are earth's 3 main layers?
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The crust, the mantle, and the core
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What are the five main layers based on stiffness?
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The lithosphere, upper mantle, lower mantle, outer core, and the inner core
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focal mechanism
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inelastic deformation in the source region that generates the seismic waves
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fault-plane solution
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slip vector
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how do we know that earth has different layers?
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if earth had the same composition and layers throughout, we would see the seismic waves move through earth in a straight line
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what are shadow zones?
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areas that dont experience body waves
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what are metcorites?
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iron - rich rock materials; tow kinds, stony and metallic
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where is all the iron?
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in the core
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what are the dangers of earthquakes?
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seismic shaking
liquefaction landslides/mudslides tsunamis |
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where is the ring of fire located?
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along the pacific plate boundary
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what is the composition of magma?
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melted mineral crystals
dissolved gases water |
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what are 3 factors that affect formation?
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heat, pressure, water content
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what determines whether an eruption is gentle or violent?
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the magma's composition and its temp
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what affects viscosity?
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composition and temp. sticky lava creates more violent eruptions
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what are some volcanic landforms?
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caldras, volcanic necks, lava plateaus
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what are calderas?
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depressions in a volcanic mountain
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what are volcanic necks?
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magma hardens and is exposed at the surface. leftover rock in pipe doesnt erode away with the rest of the volcano
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lava plateaus
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large diffs, layers of kark, volcanic rock. produced by multiple basaltic lava eruptions
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plutons
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results from colling + hardening magma beneath earth's surface. forms in continental crust, magma forms slowley and crystallizes
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what are the 3 types of plutons?
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sills, laccoliths, and dikes
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how are plutons classified?
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according to size, shape, and relationship to surrounding layers
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what are sills?
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magma inturdes between rock layers close to the surface, form only at shallow depths, pressure from overlying rocks is low.
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laccoliths
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lens-shaped pluton, pushes upper rocks upward, collects in bulges, magma has a higher viscosity
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what are dikes?
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pluton that forms when magma moves into fractures and crosses through otherlayers, sheetlike; range in thickness
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what are batholiths?
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largest bodies of intrusive igneous rock, very thick, large surface exposer, plutons begin as blobs of magma deep beneath the surface, forms irregular masses, forms granitic rock, core of many mountain ranges
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what is a basaltic composition?
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less than 50% silica content, lowest viscosity, 1-2% gas content, quiet eruptions
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What is an andesitic composition?
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60% silica content, middle speed viscostiy, 3-4% gas content, explosive eruptions
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what is a granitic composition?
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70% silica composition, highest viscosity, 4-6%gas content, explosive eruption
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what are 3 factors that affect melting?
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temp, pressure, and composition
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pahoehoe Aa lava
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rope texture on the surface
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Pyroclastics tephra
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blocks, bombs, lapili/cinders, ash (size)
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Sheild volcano
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low angle slopes, composed mostly of basaltic lava flows from single or multiple vents; hot, low viscosity magma/quiet eruptions; generally on the ocean floor
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Lava plateaus/ flood basalts
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fissure eruption instead of single vent over thousands of years. same conditions as a shield volcano
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composite cone/stratovolcano
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volcanoes on continents over land-ocean subduction zones. built up by alternating layers of lava flows. violent explosive eruptions; steeper slopes; built up over tens to thousands of years; granitic or andesidic
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cinder cones
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formed by gas-rich lava of any composition; built of pyroclastics with lots of gas holes; generally short lived eruptions
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lava domes
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very viscous magma, piles up in dome shape, YELLOWSTONE NATIONAL PARK
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Lava Destructions
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pyroclastics, lahars/mudflows, poisiness hot gases, pyroclastic flows
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Harry Hess
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Respected geologist, discovered ocean ridges, and trenches, discovered that all oceanic rocks are younger than expected
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Alfred wagner
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German scientist, continental drift hypothesis, the continents had once been formed together in one super continent called pangea
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What is some evidence for continental drift?
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Similar fossils on different continents, similar types of rock, traces of glaciation on widely spread landmasses
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What was the problem with wagners hypothesis?
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He couldn't provide evidence
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What is a sonar?
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Sound Navigation and Ranging
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What drives continental drift?
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Convection currents
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When landmasses split they form _________
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Oceans
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What are the four pieces of evidence that Wagner used?
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Fit of the continents, fossil evidence, evidence from rocks, climatic evidence
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Divergent plate boundaries
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Plates move apart, creates ocean ridges, rift valleys, and oceans
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