Untitled Flashcards Set

Evidence to support plate tectonics

1. Continental Coastlines
2. Fossils

What about continental coastlines supports plate tectonics?

the shapes of South America and Africa's coasts are similar - they fit together like a puzzle

What about fossils supports plate tectonics?

1. The same fossils are seen across separate continents
2. The age of rocks are symmetrical across mid-ocean ridges

How are earthquakes distributed?

They are concentrated around plate boundaries and are located based on shifting tectonic plates

Characterize spreading centers (divergent boundaries)

New seafloor is generated

Characterize mid-ocean ridges

fresh magma comes up and crust is slightly raised

characterize subduction zones

old seafloor is recycled. The plates slip which results in earthquakes. Because material is pushed down, magma rises.

Transform plate boundaries

2 separate plates slide past each other generating earthquakes

layers of the earth

crust, mantle, core

How do body waves travel through the earth

travel deep into earth, faster, reflected within the earth

How do surface waves travel through the earth

only travel on the surface, spread, slower

How do S-waves react?

reflected

How do P-waves react?

Refracted

Two types of deformation

Brittle and Ductile

Brittle

Fault

Ductile

Fold

What are formed under temp and pressure?

Metamorphic rocks

hot and long =

ductile (fold)

cold and short =

brittle (fault)

How many mm in a cm

10 mm=1cm

Half-rate formula

Distance/time (km/ma)

Total Velocity Equation

1/2 rate x 2

. A fundamental premise of plate tectonics is that the Earth's surface is made of distinct plates. What are the kinds of evidence/observations led geoscientists to conclude this?

-The presence of fossil evidence as well as physical boundaries for continents and chains of seismic activity, they can fit together and plants, sediments

2. Where these plates interact (at their active boundaries) is where a significant fraction of the tectonic activity occurs. There are 3 basic active plate boundaries types. What are they and how would you describe the large-scale motions at each?

-Divergent- move apart
-Convergent- come together
-Transform- slide past each other

3. What are the characteristics of the three types of plate boundaries in terms of plate motions, association of earthquakes and volcanoes, and presence or absence of mountains (or other distinctive features)?

-Divergent- results in mid ocean ridges, lava rises out of faults created by plates moving apart
-Convergent- subduction zones, causes higher plate to rise, volcanic activity from falling plate common. Earthquakes can result from sudden slips of the footwall.
-Transform-plates move past each other causing earthquakes, mountains or valleys not common.

4. What does the orientation of volcanic island chains indicate?

-presences of a convergent plate boundary, which way the plate is moving

5. Can you distinguish the different plate margins from map and elevation data?

Top is above sea, bath, below sea.

6. What is convection, how does it work (think of the analogies we used in class)?

-the heating and cooling of rock creating a cycling motion. Gravity pulls the upper cooler rock down (because it's denser) and then heats it, causing it to rise (less dense), creating a cycling motion

7. Why is convection relevant to plate tectonics?

-convection drives the movement of plate tectonics, causing the rock to move either apart, together, or past each other

8. Be able to identify and explain seafloor features and other tectonic elements on continents and relate these to convection and plate tectonics.

-seafloor features are effected by plate tectonics as well, for example divergent plate boundaries result in mid ocean ridges

9. Understand the details of subduction and sea floor spreading, in terms of large-scale physical processes (i.e., convection).

-Seafloor spreading is the result in a counter clock wise and clockwise convection zone

10. How (and why) do continents grow continuously larger through time while ocean basins grow and shrink through the actions of plate tectonics?

-plate margins are continuously rising more rock to the surface as magma, but no processes are shrinking continent size, only causing them to grow larger

1. What is an earthquake? What are the different ways that seismic waves can be generated (i.e., possible sources)?

-earthquakes are seismic waves created by the slipping of rock on fault boundaries (created by tectonic activity). They come from normal faults slipping reverse faults, and strike slip faults. The can also occur from volcanic eruptions, landslides, meteoroid impacts, and explosions

2. How do location of earthquakes relate to the 3 types of plate boundaries? How do earthquake depths help differentiate convergent plate boundaries from others?

-The depth of the earthquake is an indication of the type of boundary. Deep earthquakes occur at subduction zones (because the plates are moving down), strike slip faults create shallower earthquakes.

3. What is the difference between the lithosphere and asthenosphere, and how is this distinction related to the crust and mantle (think mechanical vs. compositional)?

-Lithosphere-mechanically ridged and solid, strong-crust
-Asthenosphere- Partially molten and weak.-mantle

4. There are two major classes of faults and each of these has two types within each class. What are they and how would you recognize one from the other?

vertical faults- Normal and reverse and thrust faults- Normal faults move apart, with a hanging wall last. Reverse faults have a foot wall last, and are being compressed.
-Strike slip faults- left lateral and right lateral. Whichever moved in is the lateral

5. What is the epicenter and focus of an earthquake?

-the epicenter is the point directly above where the earthquake took place. The focus(hypocenter) is the actual point at correct depth

6. P and S waves are seismic body waves. Which travels faster? How do the particles move in each as the wave propagates forward? Where in the Earth does each type of wave travel?

-P-waves are the fastest and subsequently arrives first. P-waves compress the particles in the earth's interior. Travels through solids, liquids, and gases.
-S-waves are slow, arrive second. These are the shear waves, causing a shaking motion. Also in the interior, but not through liquids (so not through the outer mantle)

7. How is the severity of shaking related to the earth material under a given site?

-The material the earthquake is around can cause more shaking, for example, more compact earth will be affected by the shaking more than looser sandy ground (closer to liquid)

8. What is the magnitude scale for an earthquake? How does energy increase with increasing magnitude?

Magnitude is the maximum S-wave amplitude. Each level is 10x greater than the last. The amount of energy release is 31.7x between each whole number

9. How is magnitude related to frequency of earthquakes?

The wavelength of the highest earthquake is how magnitude is measured

10. What is a tsunami and what causes them?

-columns of waves created by fault movement. They radiated away from the fault until the energy dissipates or collides into a surface.

11. In general, where do earthquakes occur on Earth? What about within North America?

-Along fault lines. New Madrid fault and the san Andrea's fault

12. What can we predict about earthquakes? What can't we predict yet?

-We can study timeframes to estimate a pattern of when earthquakes should happen in specific places. Pretty much only tells us when an earthquake is due. We can't predict exact dates, how strong it'll be or if it'll even happen.

13. What is refraction, and how does this work with seismic waves?

-Seismic waves hit either slower (more dense) or faster (less dense) material and refract (bend) through these materials

14. Why are there P and S wave seismic shadow zones and why are they not exactly the same?

-P-wave shadow zones are areas where the waves do not reach since they are refracted through the core, and miss sections of earth because their trajectory changes
-S-wave shadow zones are where S-waves hit the outer mantle and stop because it is liquid

15. What do the major seismic velocity discontinuities define in the Earth?

-Where the liquid outer core is.

16. What is the large scale structure of the Earth as understood from seismic waves?

- Earth has many layers of different composition

1. What are stress and strain and how are they related?Stress- The amount of force applied to an area. (actions)Stress leads to strain or brittle and ductile deformations (reaction)2. Describe what happens to an object during shear, tensional and compressive stress?-Shear- Objects sides are pulled in different directions-Tension- object is pulled apart-compression- Object is pushed together3. What is the difference between elastic, ductile and brittle strain (What happens to a rock)?-Elastic- strain pulls object apart but does little long term damage-Brittle- Rock inadvertently cracks apart-ductile- Rock acts close to a liquid, assuming the resulting shape due to the strain4. What is the brittle-ductile transition, and what factors control which type of deformation is dominant?-The transition zone between brittle and ductile rock. Heat, pressure, material all can effect dominate type5. What is a fold? Does it result form a brittle or ductile process?-Ductile Compression, folds of earth6. What is a fault? Does it result form a brittle or ductile process?-cracks in the earth caused by extension, compression or tilting. Brittle7. What is the difference between a joint and fault?-Faults are bigger, joints are just cracks, joints have no movements, faults are subject to tectonic forces 8. What characterizes a strike-slip vs. a dip-slip fault?-Strike slip faults move horizontally past each other, dip slips moved vertically9. What's a hanging wall? A footwall?-Hanging wall you'd have your lantern on, footwall you'd climb on10. What are anticlines and synclines? What are the identified parts of a fold? Anticline is shaped like an A New rocks are at the top, syncline is shaped like a U/V new rock in the middle11. In the real world, faults can often generate folds at the same time. How does this work?-Movement of faults can either dip below or rise above, creating either anticlines or synclines12. How is high elevation topography generated? What are local mountain building processes contrasted with regional ones?-high elevations are general formed by constant warm mantle faulting. Local mountains are created by a single fault or single event, while regional mountains are created by constant tectonic pressure such as a subduction zone.13. How can elevation be reduced through erosion and also through tectonics?-Erosion will carry away sediment from mountains, shrinking them in size. Divergent plate boundaries can also break mountains apart, shrinking them in size. Earthquakes and other events also have the potential of causing mountains to collapse.14. What shape to mountain belts take? What type of plate margins are mountains most often associated with?-Strings. Convergent15. What are the most obvious differences between very old and young mountains?-older mountains have been eroded more and thus are not as tall as younger mountains16. What happens to the Earth's crust when mountains are formed?-Its pushed into the air, folded together, and rapidly cools17. When mountain belts erode what happens to the crust below?-the crust is exposed?Describe the evidence provided by continental coastlines that supports plate tectonics. The shapes of South America and Africa's coasts are similar and t together like a puzzle. How do fossils support the theory of plate tectonics? The same fossils are found across separate continents, and the age of rocks is symmetrical across mid-ocean ridges. Characterize the distribution of earthquakes in relation to plate tectonics. Earthquakes are concentrated around plate boundaries and occur based on the shifting of tectonic plates. What occurs at spreading centers (divergent boundaries)? New seaoor is generated. How are mid-ocean ridges characterized? Fresh magma comes up, and the crust is slightly raised. What happens in subduction zones? Old seaoor is recycled, plates slip resulting in earthquakes, and magma rises due to material being pushed down. Describe the process occurring at transform plate boundaries. Two separate plates slide past each other, generating earthquakes. What are the three main layers of the Earth? Crust, mantle, and core. How do body waves travel through the Earth? Body waves travel deep into the Earth, are faster, and are reected within the Earth. How do surface waves travel through the Earth? Surface waves only travel on the surface, spread out, and are slower. What is the reaction of S-waves when they encounter dierent materials? S-waves are reected. What is the reaction of P-waves when they encounter dierent materials? P-waves are refracted. Dene the two types of deformation in geological terms. Brittle deformation results in faults, while ductile deformation results in folds. What conditions lead to brittle deformation? Brittle deformation occurs under cold and short conditions. What conditions lead to ductile deformation? Ductile deformation occurs under hot and long conditions. How many millimeters are in a centimeter? There are 10 millimeters in 1 centimeter. What is the formula for calculating half-rate? Distance divided by time (km/ma). How is total velocity calculated in relation to half-rate? Total velocity is calculated as 1/2 rate multiplied by 2. What fundamental premise supports the theory of plate tectonics? The Earth's surface is made of distinct plates, supported by fossil evidence, physical boundaries, and seismic activity. Identify the three basic types of active plate boundaries and their large-scale motions. Divergent boundaries move apart, convergent boundaries come together, and transform boundaries slide past each other. What are the characteristics of the three types of plate boundaries in terms of tectonic activity? Divergent boundaries are associated with seaoor spreading, convergent boundaries with subduction and mountain formation, and transform boundaries with earthquakes. Describe the result of divergent plate boundaries. Divergent plate boundaries result in midocean ridges where lava rises out of faults created by plates moving apart. Explain the process that occurs at convergent plate boundaries. At convergent plate boundaries, subduction zones form, causing the higher plate to rise and leading to volcanic activity from the falling plate. Earthquakes can occur from sudden slips of the footwall. What happens at transform plate boundaries? At transform plate boundaries, plates move past each other, which can cause earthquakes, but typically does not result in the formation of mountains or valleys. How does the orientation of volcanic island chains indicate plate movement? The orientation of volcanic island chains indicates the presence of a convergent plate boundary and shows the direction in which the plate is moving. Can map and elevation data help distinguish dierent plate margins? Yes, map and elevation data can distinguish dierent plate margins, with features such as land above sea level, bathymetric features below sea level. Dene convection in the context of geology. Convection in geology refers to the heating and cooling of rock, creating a cycling motion where gravity pulls cooler, denser rock down, heats it, and causes it to rise as it becomes less dense. How is convection relevant to plate tectonics? Convection drives the movement of plate tectonics, causing rocks to move apart, come together, or slide past each other. Identify the relationship between seaoor features and plate tectonics. Seaoor features are aected by plate tectonics; for example, divergent plate boundaries lead to the formation of midocean ridges. Explain the processes of subduction and seaoor spreading in relation to convection. Seaoor spreading occurs as a result of counterclockwise and clockwise convection zones, which drive the movement of tectonic plates. How do continents grow larger over time while ocean basins change size? Continents grow larger as plate margins continuously rise more rock to the surface as magma, while no processes are shrinking continent size. Dene an earthquake and its possible sources. An earthquake is a seismic wave created by the slipping of rock on fault boundaries due to tectonic activity. Possible sources include normal faults, reverse faults, strike-slip faults, volcanic eruptions, landslides, meteoroid impacts, and explosions. How does the location of earthquakes relate to the three types of plate boundaries? The location of earthquakes is closely related to the three types of plate boundaries, as each boundary type has distinct seismic activity patterns. Describe how earthquake depths can dierentiate convergent plate boundaries from other types. The depth of an earthquake indicates the type of boundary; deep earthquakes occur at subduction zones where plates move down, while shallower earthquakes are associated with strike-slip faults. Dene the lithosphere and asthenosphere and explain their relationship to the crust and mantle. The lithosphere is mechanically rigid and solid, representing the crust, while the asthenosphere is partially molten and weak, corresponding to the mantle. Identify the two major classes of faults and their types. The two major classes of faults are vertical faults (which include normal and reverse faults) and strike-slip faults (which include left lateral and right lateral faults). Normal faults move apart, while reverse faults are compressed. Explain the dierence between the epicenter and focus of an earthquake. The epicenter is the point directly above where the earthquake occurs, while the focus (or hypocenter) is the actual point at the correct depth where the earthquake originates. Which seismic body wave travels faster, Pwaves or S-waves, and how do they move particles in the Earth? P-waves are the fastest and arrive rst, compressing particles in the Earth's interior. S-waves are slower, arrive second, and cause a shaking motion as they move particles. Discuss how the severity of shaking during an earthquake is related to the earth material at a site. The type of earth material aects shaking severity; more compact earth experiences more shaking than looser sandy ground, which behaves more like a liquid. What is the magnitude scale for an earthquake and how does energy increase with magnitude? The magnitude scale measures the maximum S-wave amplitude, with each level being 10 times greater than the last, and energy release increases by a factor of 31.7 between each whole number. How is earthquake magnitude related to the frequency of earthquakes? Magnitude is measured by the wavelength of the highest earthquake, indicating that higher magnitudes are less frequent. Dene a tsunami and explain what causes them. A tsunami is a series of ocean waves caused by large disturbances such as underwater earthquakes, volcanic eruptions, or landslides. Describe the movement of waves created by fault movement. Columns of waves radiate away from the fault until the energy dissipates or collides into a surface. Identify the general locations where earthquakes occur on Earth. Earthquakes generally occur along fault lines. Name two signicant fault lines in North America. The New Madrid fault and the San Andreas fault. Explain what can be predicted about earthquakes. We can estimate timeframes and patterns for when earthquakes should happen in specic places. What limitations exist in predicting earthquakes? We cannot predict exact dates, the strength of the earthquake, or if it will even happen. Dene refraction in the context of seismic waves. Refraction occurs when seismic waves hit materials of dierent densities, causing them to bend. Describe the reason for P and S wave seismic shadow zones. P-wave shadow zones occur because waves are refracted through the core, while S-wave shadow zones exist because S-waves cannot pass through the liquid outer mantle. What do major seismic velocity discontinuities indicate about the Earth's structure? They dene the location of the liquid outer core. Summarize the large-scale structure of the Earth as understood from seismic waves. The Earth consists of many layers with dierent compositions. Dene stress and strain in geological terms. Stress is the amount of force applied to an area, while strain is the reaction to that stress, leading to deformations. Describe the eects of shear stress on an object. Shear stress causes the sides of an object to be pulled in dierent directions. What happens to an object under tensional stress? Tensional stress pulls the object apart. Explain the eect of compressive stress on an object. Compressive stress pushes the object together. Dierentiate between elastic, ductile, and brittle strain in rocks. Elastic strain causes little long-term damage, ductile strain allows rocks to ow like a liquid, and brittle strain results in cracks. What is the brittle-ductile transition? It is the transition zone between brittle and ductile rock, inuenced by heat, pressure, and material properties. Dene a fold in geological terms. A fold is a structure that results from ductile deformation processes. Describe ductile compression in geological terms. Ductile compression refers to the folding of earth materials under stress, resulting in bends and folds in the rock layers. Dene a fault in geology. A fault is a crack in the earth's crust caused by tectonic forces such as extension, compression, or tilting, and it results from a brittle process. Explain the dierence between a joint and a fault. Faults are larger fractures in the earth's crust that involve movement, while joints are smaller cracks that do not exhibit any movement. Characterize strike-slip and dip-slip faults. Strike-slip faults involve horizontal movement of rock masses past each other, while dip-slip faults involve vertical movement. What is a hanging wall and a footwall in geological terms? The hanging wall is the block of rock that lies above a fault, where one might hang a lantern, while the footwall is the block below the fault, which one would climb on. Dene anticlines and synclines in geology.