earth science HW 7 – Flashcards
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At a divergent boundary, what is the relative motion of the plates on each side of the boundary?
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The plates move away from each other.
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Which of the following statements about divergent boundaries is true?
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New ocean crust is created at a divergent boundary.
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Movement of plates away from each other at divergent boundaries typically shows which of the following average velocities?
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5 cm per year
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When moving away from a divergent boundary in either direction, which of the following statements is true?
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The rocks increase in age.
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What are the two primary types of waves generated by earthquakes?
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surface waves and body waves
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Name two types of body waves.
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P waves and S waves
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Where do body waves and surface waves travel?
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Body waves travel within Earth, and surface waves travel along Earth's surface.
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What do vertical and horizontal surface waves have in common?
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Both waves travel along Earth's surface and decrease in amplitude with depth below the surface.
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How do rocks within Earth change as P waves pass?
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Rocks within Earth both expand and contract as P waves pass.
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How does rock within Earth change as S waves pass?
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Rocks within Earth are displaced up and down as S waves pass.
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How are S waves and vertical surface waves different?
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S waves are body waves, whereas vertical surface waves are surface waves. The amplitude of S waves does not decrease with depth, but the amplitude of vertical surface waves does decrease with depth.
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What is the relationship between the crust and lithosphere?
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The crust is part of the lithosphere.
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Complete this statement: Divergence is to moving away as convergence is to _______.
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moving toward
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Plates move apart at __________ boundaries, move together at __________ boundaries, and move side-by-side at __________ boundaries.
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divergent/convergent/transform
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Which geologic features are associated with divergent boundaries?
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mid-ocean ridges and continental rift valleys
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Which geologic features are associated with convergent boundaries?
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ocean trenches and volcanoes
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Where is the youngest ocean floor found?
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along the crest of mid-ocean ridges
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What would happen to Earth if ocean floor were created at divergent boundaries at a faster rate than it is destroyed at convergent boundaries?
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The Earth would increase in volume.
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What is a volcanic arc?
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a row of volcanoes that forms on the overriding plate near a subduction zone
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Which of the following mountain ranges are examples of continental arcs?
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Andes and Cascades
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How do plates move at divergent plate boundaries?
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Plates move apart.
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How do plates move at convergent plate boundaries?
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Plates move toward one another.
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How do plates move at transform plate boundaries?
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Plates slide past one another.
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In general, where do earthquakes AND volcanic eruptions occur?
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convergent plate boundaries and divergent plate boundaries
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What forms at divergent plate boundaries?
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new oceanic lithosphere
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In general, where do volcanoes form in subduction zones?
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on the overriding plate, away form the convergent boundary
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Why are volcanoes NOT found at transform boundaries?
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Transform boundaries do not cause changes to the pressure, temperature, or composition of the mantle.
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The East African rift is a divergent plate boundary that is splitting the continent of Africa into two pieces. What will eventually form around this divergent boundary?
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an ocean
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Which of the following statements regarding transform plate boundaries is not correct?
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New oceanic crust is formed at transform plate boundaries.
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Which of the following statements regarding transform plate boundaries is correct?
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Earthquakes are a common occurrence along transform plate boundaries.
At transform plate boundaries, adjacent lithospheric plates slide past each other horizontally.
Transform plate boundaries can occur within continental crust.
Transform plate boundaries connect two segments of the oceanic ridge system.
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Continued movement of the continental crust on the west side of the San Andreas fault could result in which of the following features?
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an island
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The occurrence of stream channels that have been offset along a transform fault are indicative of which of the following conditions?
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opposite sides of the fault have shifted horizontally
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What type of stress is most directly associated with transform faults?
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shear stress
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Which of the following geologic processes and/or phenomena is not found at transform plate boundaries?
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volcanoes
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Which of the following geologic processes and/or phenomena is found at transform plate boundaries?
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crustal thinning
earthquakes
offset stream channels
weathering
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Which of the following lithospheric plates is not included among the seven largest?
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the Philippine plate
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Earth's lithospheric plates are composed of crust and which of the following layers?
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the outermost portion of the mantle
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Which of the following processes can be observed at the margins of lithospheric plates?
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faulting
earthquakes
volcanoes
mountain building
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In studies of rock obtained from ocean basins all over Earth, the oldest ages obtained are approximately 200 million years before the present. Why have no older oceanic rocks been discovered?
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Due to tectonic activity, rocks on the ocean floor are continually recycled.
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Currently the Juan de Fuca plate is interacting with the North American plate where inland volcanoes and deep focus earthquakes are occurring. What type of plate boundary is this?
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a convergent plate boundary
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According to the animation, what are the four primary zones in Earth's interior?
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crust, mantle, outer core, inner core
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What data provided information about the existence of different zones within Earth?
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P-wave and S-wave arrival times
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Which of the following statements about seismic wave ray paths is most accurate?
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Seismic waves move along curved ray paths because the properties of materials in the Earth change.
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Why do we believe Earth's outer core is a liquid?
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P waves slow down and refract at the boundary between the mantle and the outer core.
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S waves do not travel through the outer core.
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Why do geologists believe the inner core is solid?
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P waves refract at the boundary between the outer core and inner core.
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How could you test whether the core of another planet were completely solid?
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Set off a bomb to create seismic waves. If S waves arrive on the opposite side of the planet, then the core is solid.
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Where are tectonic plates located?
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at Earth's surface
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What are the three types of plate boundaries?
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divergent, convergent, and transform
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Which of the following statements about earthquakes with magnitude greater than 4.0 is most accurate?
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Earthquakes with magnitude greater than 4.0 occur in a pattern than correlates closely with plate boundaries.
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Which plate boundary is NOT associated with volcanic eruptions?
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transform
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Which phenomenon can explain the presence of volcanoes in the middle of the Pacific Ocean?
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hot spots
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Which type of plate boundary is most closely associated with uplifting continental regions and mountain building?
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convergent boundaries
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Which layer of Earth possesses the greatest thickness?
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mantle
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which of the following rocks best represents the typical composition of oceanic crust?
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basalt
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Which region of Earth is composed of abundant amounts of granite?
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continental crust
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what is the major source of energy that drives the movements of the lithospheric plates on Earth?
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thermal energy from within Earth
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The magnetic field of Earth is thought to originate in which of the following layers?
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outer core
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Which of the following responses best describes why the lithospheric plates are able to move around on the surface of Earth?
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Because the asthenosphere is composed of weak, hot, and dense rock, the cold, rigid, less dense lithospheric plates are capable of moving on it.
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how do we know that the outer core of Earth is liquid?
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A shadow zone exists where S waves do not arrive on the side of Earth opposite the focus of an earthquake.
