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48 Cards in this Set
- Front
- Back
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What evidence did Wegner use to support continental drift. |
Continents seem to fit together Rock bodies are continuous across continents Fossils range across continents in odd ways Continents show evidence of very different climates in the past. |
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Problems with continental drift |
Wegner had no idea how the continents were being moved. Wegner thought that the continents were moving through solid rock on the ocean floor. Other explanations at that time that made more sense. |
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What role did sea floor spreading have in plate tectonic theory? How did it help overcome shortcomings of continental drift? |
Gives us idea of how continents are being moved. Does away with problem of moving the continents through the ocean floor, because floor is moving too. |
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How do magnetic polarity reversals support the theory of plate tectonics? |
Ingenous rocks record earths magnetic polarity. Vine and Matthew's found that the magnetic polarity observed at mid Atlantic ridge matched record we see on land.
Record was mirror image on either side of the ridge. |
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Mineral Definition |
Naturally occurring Inorganic Solid Definite chemical composition Crystal form |
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Igneous
Compositions: Mafic, Intermediate, Felsic. |
Igneous: Form from molten rock
Mafic: low amounts of silica
Intermediate: medium amounts of silica.
Felsic: high amounts of silica. |
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Sedimentary rock |
Form from sediments or from chemical precipitation |
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Metamorphic rocks |
Form by applying heat and pressure to preexisting rocks |
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Igneous textures:
Fine grained
Coarse grained |
Fine grained: can't see crystals. Cooled quickly above ground.
Coarse grained: can see crystals. Cooled slowly below ground. |
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Difference between chemical and clastic sedimentary rocks. Examples of each. |
Chemical: Form from chemical precipitation. Ex. Limestone Clastic: formed from sediment being cemented together. Ex. Conglomerate, sandstone, siltstone, shale. |
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How are clastic sedimentary rocks generally classified? |
Categorized by size. |
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Name Rock for each size Pebble Sand Silt Clay |
Pebble: Conglomerate Sand: Sandstone Silt: Siltstone Clay: Shale |
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Foliated
Non foliated |
Foliated: Have a layered texture from mineral grains being forced into alignment during metamorphosis e.g. Gneiss.
Non foliaed: No alignment of mineral grains e.g. marble |
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Relationship between foilation and metamorphic grade |
Better foilation = higher grade Low heat/pressure = low grade High heat/pressure = high grade |
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Strike Slip |
Occur at transform boundary |
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Dip Slip |
Normal:common at divergent boundaries. Reverse: Common at convergent boundaries. |
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Focus |
Area along fault where slippage occurs (below ground) |
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Epicenter |
Point on ground surface above focus |
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Surface waves |
Waves that travel along surface of the earth, similar to waves in water. |
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Body waves |
Travel within (through) the earth |
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P waves |
Waves that travel by compressing material Travel relatively fast Can travel through liquid |
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S waves |
Waves that travel by displacing material at right angles to the direction they're traveling in.
Travel slow
Can't travel through liquid |
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How can you use P and S waves to determine the epicenter of an earthquake? |
Use the difference in the speed between P waves and S waves to determine how far away the earthquake epicenter is by triangulating from three different seismic stations. Greater time lag = greater distance from epicenter |
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If P waves and S waves arrive at about the same time are you close or far from the epicenter? |
Close |
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What is the difference between the Mercalli and the Richter scale? |
The Mercalli scale is qualitative and based on damage of an earthquake and how it was perceived by people. Changes based on distance from epicenter.
Richter scale is quantitative. Calculated by a formula taking into account the size of S waves and distance from epicenter. Each whole number = 30 times more energy released. |
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How do tsunamis form |
Tsunamis can be caused by:
-Tectonic forces -Earthquakes -Above and below water landslides -Meteor impact
In order for a tsunami to be generated the headwall must rebound upward during the earthquake. |
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How does viscosity determine nature of a volcanic eruption? |
Highly viscous things resist flowing (honey) low viscosity flows easily (water) Highly viscous volcanoes erupt more violently Less viscous volcanoes do not erupt violently |
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How does silica determine viscosity? |
More silica makes more viscous magma because silica tends to make chains and other structures that make it hard for lava to flow. |
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How does a magmas composition relate to its viscosity? |
Mafic magmas have low silica and are not very viscous. Felsic magmas have more silica and are very viscous. These magmas usually cool underground and do not make volcanoes. Intermediate magmas have little enough silica to make it to the surface but enough to be very explosive. |
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Shield Volcano |
Very large Not very violent Most of the material extruded is lava |
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Cinder cones |
relatively small Often associated with other volcanoes Extrude mostly pyroclastic material (ash and rock) Most numerous volcanoes on the planet. |
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Composite cone |
Combination of lava and pyroclastic material
Very explosive
Most are located around the Pacific
Medium size |
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6 ways to die in a volcano |
Gasses
lavaflows
Tephra: anything solid ejected from a volcano, from house sized boulders to ash.
Lahar: a very fast moving mud flow down the flanks of a volcano
Pyroclastic flow: high-density mixtures of, dry rock fragments and hot gases that move away from the vent that erupted them at high speeds.
Landslide |
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Relative time |
which rocks are older and which rocks are younger |
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Absolute time |
how old are the rocks |
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Law of superposition |
older rocks are on the bottom younger are on top (must be sedimentary) |
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Principal of original horizontality |
Rock layers are generally deposited horizontally |
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principal of cross cutting relationships |
When faults or igneous intrusions cut through a rock they are younger than the rock they cut. |
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Inclusion |
Pieces of rock contained within another the inclusion is older than the rock that contains it |
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Uncomformity |
An ucomformity is a gap in the rock record |
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Isotope |
Two forms of the same element, contains equal protons but different # of neutrons |
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Half life |
A half life is the amount of time it takes for half an element to decay |
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How do you use radioactive isotopes to determine the age of a rock |
Measure amount of parent and daughter isotope you have Determine how many half lives have passed Multiply the number of half lives by the length of a half life to determine the age of the rock |
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Plate Boundaries Eathquakes? Volcanoes? EX. Divergent Transform Convergent: Ocean-ocean, ocean-continent, continent-continent |
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Convective Pushing Slab Pull Ridge slide Basal drag |
Convective pushing: Occurs at mid ocean ridge as new material is brought to the surface. Slab pull: Occurs at trenches as new material is sucked down. Ridge slide: the plate is moving "down slope"driven by gravity. Basal drag: Occurs in the middle of the plate as the convection cell moves material (most important) |
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Divergent Boundaries |
Areas where plates are moving away from each other. Ex. Iceland. -Mid ocean ridges are divergent boundaries -Triple junction: things tend to split apart in threes. |
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Transform boundaries |
Area where one plate is sliding past another. Ex. San Andreas Fault CA -Lots of small shallow focus earthquakes -No volcanoes |
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Convergent Boundaries |
Areas where plates are coming together.
Continent-ocean: Oceanic meets continent and slides underneath (volcanoes and earthquakes). Ex. Andes and cascade mountains.
Ocean-ocean: Two oceanic plates come together causing a trench (volcanoes and earthquakes). Ex. Virgin islands
Continent-continent: Two continental plates collide forming mountains. (no volcanoes, earthquakes). Ex. Himilayan mountains.
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