Chapter 3 - Plate Tectonics

abyssal plains

Regions of the deep ocean characterized by smooth ocean floor are called _____.

1. Ascension of magma causes uplift of the crust. 2. Stretching of the crust causes crustal blocks to drop into faults, forming a rift. 3. Continuation of rifting splits the continent into two; a narrow ocean forms as seafloor spreading takes place. 4. Continuation of seafloor spreading increases the ocean basin as it becomes wider.

Rank the stages of continental rifting from the beginning, with the first stage on the top.

heat

Besides creating and destroying lithosphere, plate-tectonic processes also transport _____ from the center of Earth to the surface.

reversed; north to south

A compass needle pointing to the south would be the result of _____ polarity, when the magnetic field runs from _____.

transform

A fault that accommodates the horizontal movement of one tectonic plate past another is a(n) _____ fault.

If this is true, then the oldest basalt should be the farthest from the mid-ocean ridge. If this is true, the thickest sediment cover should be farthest from the mid-ocean ridge.

According to plate tectonics, oceanic crust forms from upwelling magma that spreads outward from a mid-ocean ridge. Which of the following statements support this? (Select all that apply.)

the oceanic plate subducts beneath the continental plate.

Along the boundary of an oceanic-continental convergence, _____

in an oceanic trench created by the subduction of one oceanic plate beneath another plate

An accretionary prism of sediments and oceanic crust is formed _____.

transform

An oceanic fracture zone is a former _____ fault that now has no relative motion along it.

plates, chains

As _____ move over hot spots, island _____ in oceans can be formed by volcanism.

decompression

As two oceanic plates diverge at mid-ocean ridges, melting of the rising mantle occurs due to _____.

solid mantle in the asthenosphere rises toward the surface and begins to melt due to decompression.

At mid-ocean ridges as two plates diverge, _____.

age

By comparing the patterns of magnetic reversals in a rock sequence, geologists can use the magnetic timescale shown here to estimate the ____ of a rock.

Western side: Subduction zone, Trench, Mountains Eastern side: Passive margin, Lack of tectonic activity, Wide continental shelf

Compare the tectonic settings of western and eastern South America by placing the features in the correct category

tectonics

Continental outlines and similar geology on neighboring continents supports the theory of plate

outer

Convection currents in Earth's ______ core produce the magnetic field.

two plates move toward each other

Convergent boundaries are formed when _____.

oceanic fracture zones

Cracks and steps that cross the seafloor and run at right angles to mid-ocean ridges are called _____.

magnetic

Earth's ____ poles have switched many times throughout geologic history.

surface

Earth's _____ is notable for many geologic features such as beautiful valley's, intricate coastlines, and deep ocean trenches.

southern

Glacial evidence in _____ continents that are too warm for glaciers in their current position is evidence of continental drift.

continents

Gondwana is the name given to the combination of southern _____ proposed by Wegener in his hypothesis of continental drift.

transform

Horizontal movements between plates occur at _____ faults.

Subduction brings one plate to a depth hot enough for minerals to release water; this water causes melting in the overlying asthenosphere.

How is magma created in a subduction zone?

7

How many major continents are there on Earth?

30 km/m.y

If a magnetic stripe is 120 km wide and formed over 4 million years, what would the rate of seafloor spreading be?

be the same on the other continent if the mineral deposits were formed before the continents split.

If two continents are matched and their geologies are examined, it is assumed by plate tectonics that the mineral deposits discovered on one continent will _____.

iron-rich minerals align with Earth's magnetic field.

Magnetic patterns develop on the seafloor as basaltic lava erupts and cools, and _____.

Yellow --> Divergent Red --> Convergent Green --> Transform

Match the boundary type with the color it is represented by on the map.

A --> Mid-ocean ridge B --> Deep ocean trench C --> Mountain belt, volcanoes, and earthquakes

Match the geologic feature with its location along the South American plate boundary.

ocean

Mid-ocean ridges are broad symmetrical ridges that cross _____ basins.

decreases away from the mid-ocean ridge because of the cooling and contraction of the rocks

Mid-ocean ridges are elevated above the seafloor. The elevation of the seafloor _____.

seamounts

Mountains beneath the oceans that do not reach the surface are called _____.

71

Oceans cover _____% of Earth's surface.

1 to 15 cm

Plates move _____ per year.

Volcanoes in the Andes Mountains of South America. Volcanoes of southern British Columbia. Volcanoes of the Cascade Range in the U.S. Pacific Northwest.

Select areas on Earth that represent convergent boundaries. (Choose all that apply.)

Pacific Ocean Atlantic Ocean Arctic Ocean Southern Ocean Indian Ocean

Select the five oceans of Earth from the list below.

Some asthenosphere becomes lithosphere at mid-ocean spreading centers and reenters the asthenosphere at subduction zones.

Select the statement that best describes how the process of plate tectonics circulates materials between the asthenosphere and lithosphere

continental

Some continents continue outward from the shoreline under the seawater. These submerged benches are called _____ shelves.

1. North America, South America, Europe, and Africa were all part of the same supercontinent. 2. The crust underneath the supercontinent was uplifted by underlying magma moving toward the surface. 3. The continental crust began to stretch, and a continental rift was formed. 4. The rift split the supercontinent to form a narrow ocean basin. 5. The ocean basin continued to widen through seafloor spreading.

Summarize the formation of the Atlantic Ocean by putting the following into the correct order, with the first stage on top.

subduction

The Pacific Ring of Fire is a result of _____ on both sides of the Pacific Ocean.

a string of volcanoes

The Pacific Ring of Fire is formed by _____.

two continental plates colliding and forming mountain ranges

The Tibetan and Himalaya Plateau are the result of _____.

San Andreas

The _____ _____ fault in California is a transform fault that has formed linear valleys, abrupt mountain fronts, and lines of lakes.

Mid-Atlantic Ridge

The arrow in the figure is pointing to the ______-_____ _____, where the African and South American plates are moving apart and new oceanic lithosphere is emerging from Earth's mantle.

curves and abrupt bends that appear in boundaries between plates

The boundary between two plates may not have the same characteristics in different geographic locations because of _____.

east-west or perpendicular to the ridge

The direction of spreading along the north-south ridges of the mid-ocean ridge is _____.

South America

The figure shows the movement of _____ over time to its current position, causing its unique plate tectonics.

Wegener could not explain how or why the continents moved from place to place.

The hypothesis of continental drift, as proposed by Alfred Wegener, was not accepted because _____.

seafloor spreading

The image shows the Mid-Atlantic Ridge, a submarine volcanic mountain belt that is a key location in the process of ____. This hypothesis was developed by Harry Hess and Robert Dietz.

mountains

The lack of _____ on the eastern side of South America compared to the western side demonstrate the two areas have dramatically different plate tectonic settings.

triple

The place where three plate boundaries meet is referred to as a(n) _____ junction.

subduction

The process of one plate sliding beneath another plate is called _____.

lithosphere

The process of plate tectonics circulates materials between the asthenosphere and the _____.

hot spots

The two key characteristics that island and seamount chains have in common are that they are formed by volcanism and they are near _____.

the plate moving over the hot spot that formed the Hawaiian Islands has been moving faster

The volcanic island chain known as the Hawaiian Islands differs from the Galapagos Islands cluster because _____.

alternation of the spreading segments with transform faults

The zigzag pattern of mid-ocean ridges reflects the _____.

East Africa

This geographic area is the usual example geologists discuss when describing continental rifting in its different stages.

seamount

This is the name of a volcanic island that erodes and sinks underneath the sea surface.

Divergent --> A Convergent --> B Transform --> C

Using the diagram with the figures labeled A, B, and C from left to right, match the name of the plate boundary with its figure letter.

Along continent edges and mid-ocean ridges

Using the figure, where are earthquakes more likely to occur?

parts of the lithosphere are weaker, so forces can be transmitted through plates, causing geologic activities in the weaker areas

Volcanic and earthquake activities on Earth can mostly be explained by the interaction between plates. However, volcanoes and earthquakes do occur at places other than plate boundaries. An explanation for this is _____.

Midway is the oldest of the listed islands. Kauai is younger than Midway. Kauai is closer to Kilauea than Midway.

What are three accurate pieces of information that can be obtained from the graph?

transform boundary

What specific type of plate boundary is commonly found in conjunction with mid-ocean ridges, as it works to offset spreading and plate divergence?

continental

When divergent boundaries occur on continents, the process is called _____ rifting.

collision

When two continental masses converge, it is referred to as a continental _____.

Southern continental landmasses seem to fit together like puzzle pieces. Glacial evidence exists in places that are now close to the equator, and the direction of glacial movement indicates the continents were once joined. Similar rocks and geologic structures exist in South America, Africa, and Antarctica. Fossils of animals and plants that existed more than 150 million years ago are present on several continents that are now divided by an ocean.

Which pieces of evidence supported Wegener's hypothesis of continental drift? (Choose all that apply.)

GPS satellites lasers

Which tools can be used to directly measure plate motion?

They are different ages, so they have different cooling histories.

Why do the opposite sides of a fracture zone have different elevations?

Mantle convection

_____ _____ is the slow overturning of Earth's hot, ductile interior as heated rock wells up from below, cools near the surface, and sinks back down again.

Tectonics

_____ is the study of processes that deform the crust and mantle.

tectonic

_____ plates are composed of lithosphere and move around on the asthenosphere.

subduction

Earthquakes are common along the western coast of South America as a ____ zone occurs due to oceanic lithosphere moving beneath the continent.

more

Exemplified by the western coasts of North and South America, high elevation on Earth tend to have _____ earthquake and volcanic activity than lower-elevation areas.

The driving forces must exceed the resisting forces.

In order for a tectonic plate to move, what must the relationship between the driving and resisting forces be?

boundaries

Intense geologic activity is concentrated at plate _____.

arcs

Island _____ are curving chains of mostly volcanic islands across the seafloor.

fossil

Land bridges were originally proposed to explain _____ evidence as provided by the presence of Mesosauris and Glossopteris on continents separated by large oceans. One supercontinent that split apart by continental drift better explains this evidence.

volcanoes

Large composite _____ of the Andes Mountains of South America and the Cascade Range of Washington and Oregon are the result of oceanic-continental plate convergence.

boundaries

The location of earthquakes is a better guide to plate _____ than the location of volcanoes.

False

True or false: Curved island arcs and linear island chains are very similar in their character and formation.

convergent boundary

When two ocean plates come together, a _____ is formed.

arc

When two oceanic plates converge, a curved belt of volcanic islands called an island _____ can be formed.

Stretching of the crust causes crustal blocks to drop down. If rifting continues, the continent can be split into two pieces. Rifting begins with a broad uplift as magma ascends.

Which of the following are characteristics of continental rifting? (Choose all that apply.)

Subducting plates move faster than nonsubducting plates. Subducting oceanic lithosphere is denser than asthenosphere. Gravity is a major force in slab pull.

Which of the following are characteristics of slab pull? (Select all that apply.)

Two different transform faults A subduction zone

Which of the following are involved in the Mendocino triple junction? (Choose all that apply.)

As the plates move apart, solid lithosphere moved upward into the asthenosphere.

Which of the following is not a characteristic of a mid-ocean divergent boundary?

There are few earthquakes on the abyssal plains. Ocean trenches and associated island arcs have numerous earthquakes. Earthquakes are common along the western coasts of North and South America,

Which of the following statements about the distribution of earthquakes are accurate? (Choose all that apply.)

Volcanism occurs along mid-ocean ridges. Many volcanoes along the edge of the Pacific Ocean are associated with earthquakes. There is a large volcanic belt along the west coasts of North and South America.

Which of the following statements are accurate about volcano distributions on Earth? (Choose all that apply.)

Buoyant magma rises into the overlying plate. One of the two oceanic plates subducts beneath the other plate. Temperature increases within the subduction zone, releasing water, which induces melting. An oceanic trench is formed and sediments begin to collect.

Which of the following statements are accurate about what happens when two oceanic plates converge? (Choose all that apply.)

Smooth regions of the ocean floor are called abyssal plains. Mid-ocean ridges and their fracture zones encircle much of the globe. Seamounts can be part of island arcs. Continents and oceans can have elevated areas called plateaus. Continental shelves are extensions of continents beneath the oceans.

Which of the following statements are true about characteristic geologic features with respect to their locations on Earth? (Select all that apply.)

1 3

Which of the magnetic striped shown in the diagram have normal magnetic polarity? Assume the strip marked "1" is present day.

A plate sliding away from the topographically high ridge and pushing the plate outward.

Which one of the following refers to the process of ridge push?