ch 02

A fracture zone is a continuous linear feature of segments of active transform faults and ______.

"fossil" or inactive transform faults

Select all the lines of evidence Wegener used to support his theory of continental drift.

- The fossils of plants and animals - Patterns of glaciation - The geographic fit of the continents

Match the paleogeographic feature to the correct description.

. Pangaea: A massive single land continent.2. Panthalassa: A massive ocean covering most of the Earth (now the Pacific)3. Gondwana: A supercontinent that contained the now Southern Hemisphere continents.4. Laurasia: A supercontinent that contained the now Northern Hemisphere continents.

The characteristics listen below apply either to active or passive margins. Select all the characteristics of active margins:

1. Represents a plate boundary.2. Modified by tectonic movement and volcanoes.3. Ocean trenches possible

Select all the statements below that are true regarding seafloor spreading rates.

1. Spreading rates vary across the Earth in time.2. The average spreading rate is about 5 cm per year.

Match the type of convergent plate boundary to its description:

1: Ocean-ocean: This convergent boundary tends to form island arc volcanism as the subducting slab melts and the molten material rises up through the overriding plate.2: Ocean-continent: The volcanoes formed here have an andesitic composition resulting from the mixing of granite and the basaltic magma from the subduction zone melting.3. Continent-continent: This type of boundary forms after the complete closing of a ocean during other types of convergence.

The average seafloor spreading rate is between ______ per year

2 and 10 cm

tethys

An ocean occupying an indentation in Pangaea

Beneath the crust is the mantle. The upper surface of the mantle was identified by the change in seismic properties resulting from the increased density of the rocks there. This upper surface of the mantle is called the ------.

Moho

Francis Bacon, George Buffon, Alexander von Humboldt

Noticed the possible "fit" between the African and South American continents

Select all the statements below that are true regarding continental and oceanic crust.

Oceanic crust is denser than continental crust. Oceanic crust is largely composed of basalt.

Harry Hess

Promoted the concept of large thermal circulation cells within Earth that are heated by radioactivity and heat from the core Promoted the concept of large thermal circulation cells within Earth that are heated by radioactivity and heat from the core

F. J. Vine and D. H. Matthew

Proposed that the matching magnetic strips on either side of a spreading center represented a recording of polarity reversals Proposed that the matching magnetic strips on either side of a spreading center represented a recording of polarity reversals

Edward Suess

Proposed that the southern continents had once joined into a single continent now called Gondwanaland

Alfred Wegener

Proposed the theory of continental drift

Select the two ideas below that plate tectonics incorporates and builds upon.

Seafloor spreading Continental drift

Rodinia

The supercontinent that existed before Pangaea

A major line of evidence for continental drift is that unusual sequences of rocks, unique fossils, and glacial deposits lined up ______.

across ocean basins

The youngest sea floor can be found ______.

at spreading centers

Pillow lavas are created from _____ lava that is extruded slowly onto the ocean floor.

basaltic

Volcanic islands in the ocean that move off of the hotspots that formed them will

be worn down by water and wave erosion to form flat-topped seamounts (guyots)

The majority of the earthquakes in the world occur at or near the ______.

boundaries of tectonic plates

The Himalaya Mountains are the result of a ______ convergence.

continent-continent

Tectonic plates move toward each other at ______ boundaries

convergent

_______ plate boundaries are where tectonic plates move toward one another; plate boundaries are where the plates slide past each other; _____ divergent plate boundaries are where plates move away from each other.

convergent transform

Rank Earth's layers by their average densities. Place the least dense on top.

crust mantle core

At convergent plate boundaries, the tectonic plates are moving toward each other. What happens at these boundaries depends heavily on the ______ of each plate.

density

The boundaries of the tectonic plates can be outlined by plotting the locations of ______ on a map.

earthquakes

A continental zone is associated with mantle upwelling, weakening crust, and extensional forces.

rift

A ______ is a region on land where a new divergent boundary is forming due to extensional forces related to upwelling at the base of the continental crust and lithosphere.

rift zone

Hotspot volcanoes are likely the result of ______.

rising magma from the mantle Reason: The chemistry of hotspot magma suggests a possible start at the core-mantle boundary.

A classic example of a transform plate boundary is the fault formed by the Pacific Plate sliding by the North American Plate at the ______.

san andreas fault

Transform boundaries occur where two tectonic plates ______ past one another. This motion does not always occur freely, and thus ______ faults are formed.

slide transform

Transform faults within a ridge system form because of changes in the speed and direction of moving plates on a surface, ______ i.e, Earth.

spherical

The lateral movement of the oceanic lithosphere near ocean ridges is called seafloor______.

spreading

The areas in which new sea floor and oceanic lithosphere are formed are called _______ centers, and the areas where older oceanic lithosphere is recycled as it descends and melts are called ______ zones.

spreading subduction

______boundaries in marine settings create new sea floor at the _____ centers.

Divergent spreading

True or false: Continents move through the basalt of the sea floor as they move about the surface of Earth.

False Reason: Continents are more like passengers on a conveyor belt.

A place where seafloor spreading at a mid-ocean ridge can be seen on land is________

Iceland

Select all the causes below that correctly describe why transform faults may occur.

Changes in speed and direction for plates as they move on a spherical surface Variations in strength or location of convection cells in Earth Collisions between sections of the lithosphere

Primarily composed of granite, continental ------ crust has a lower density and is thicker than ----- crust, which is primarily composed of basalt.

Continental oceanic

Select the analogy below that describes how continents move about the surface of Earth.

Continents are passengers on the lithosphere much like boxes on a conveyor belt.

True or false: Since hotspots operate independently of the plate tectonic system, they are not useful for studying plate motion.

false True or false: Since hotspots operate independently of the plate tectonic system, they are not useful for studying plate motion.

The inactive and active transform faults between two sections of an ocean ridge crest can form a long continuous linear feature called a ______ zone.

fracture

The two major models for a mechanism to drive plate tectonics are the ridge-push, slab-pull and the convection models. The convection model relies on ______ between the top of the convecting cell and the base of the lithospheric plate, and the push/pull model relies on the ridge ______ and pushing the plate outward as the ridge falls in elevation.

friction cooling

______ result in volcanic activity that may operate independently of plate boundaries. These volcanoes can form anywhere on a tectonic plate.

hot spots

The Hawaiian Islands to the west of the main island have inactive volcanoes because they have moved off of the .

hotspot

The point within Earth where an earthquake occurs is called the ______ and the point on Earth's surface directly above this location is called the ______.

hypocenter epicenter

n the Northern Hemisphere, the Mid-Atlantic Ridge cuts across the country of ______.

iceland

A major difference between the ridge-push, slab-pull model and the convection model is the ridge-push, slab-pull model ______.

includes the decrease in elevation from the ridge to the rest of the plate as a factor

The age of the sea floor ______ away from the ocean spreading centers.

increases

The Mohorovičić discontinuity (the Moho) is the upper surface of the

mantle

The magnetic field of Earth is ______.

not constant. The locations of the north and south magnetic poles change over time, as does their strength

Spreading centers are where new ______ lithosphere is created, and ______ zones are where older oceanic crust descends into the mantle and is recycled

oceanic subduction

The relatively calm trailing edge of continents are called ______ margins, while the leading edge of continents are called ______ margins.

passive active

The relatively calm trailing edge of continents are called _______ margins, while the leading edge of continents are called ______ margins.

passive active

A convection cell in the mantle is the ______.

pattern of movement mantle material takes as it heats and cools

If you know the age of the rocks on a particular seamount and the distance it is from its associated hotspot, you can determine the rate of _____ motion

plate

The theory of _____ ______ incorporates the ideas of both seafloor spreading and continental drift into a unified model.

plate tectonic

Continental drift is the theory that ______.

the continents are slowly moving about Earth's surface

The main reason continental drift was not widely accepted at the time of its proposal was ______.

there was not an acceptable mechanism identified for causing the drift

The ______ of oceanic lithosphere increase(s) with a rate proportional to the square root of its age.

thickness

The San Andreas Fault in California is an example of a long ______ fault.

transform

The ocean ridge system is broken into sections and connected by _____ boundaries; these are the areas where the new crusts

transform

The ocean ridge system is broken into sections and connected by _____ boundaries; these are the areas where the new crusts slide past one another.

transfrom

Ocean-ocean and ocean-continent convergent boundaries form ocean ______, and continent-continent convergent boundaries form ______.

trenches mountains

Ocean-ocean and ocean-continent convergent boundaries form ocean ______, and continent-continent convergent boundaries form ______.

trenches; mountains

True or false: The thickness of the oceanic lithosphere increases with age

true

The Hawaiian Island chain is the result of a ______.

volcanic hotspot

Guyots (flat-topped seamounts) are the result of ______.

volcanic islands being eroded after moving off the hotspot that formed them

The asthenosphere is the ______.

weak, deformable region in the mantle