Chapter 3: Plate Tectonics

Earthquakes are more common along edges of continents and _____ ridges.

mid-ocean

Oceanic fracture zones are cracks and steps that cross the seafloor and run mostly at right angles to _____ ridges

mid-ocean

A mountain beneath the ocean that does not reach the surface is called a _____. It may be a worn-down island or may never have been tall enough to break the water surface.

seamount

The place where three plate boundaries meet is referred to as a _____ junction

triple

Island and seamount chains are formed by _____ and hot spot activity.

volcanism

Abyssal plains are the relatively smooth surfaces of the _____ floor.

ocean

Convergent boundaries are formed when ______.

two plates move toward each other

There are _ continents on Earth

7

After Antarctica, South America, and North America, the other four continents on Earth are ______, _____, _____, and _____

Europe, Asia, Australia, Africa

The following are characteristics of continental rifting:

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

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

San, Andreas

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

Tectonic

The type of plate movement that occurs at transform faults is _____

horizontal

Which of the following statements about the distribution of earthquakes are accurate?

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

The areas on Earth that represent convergent boundaries are:

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

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

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

True or false: Continental drift is proven by evidence showing that continents have plowed through the ocean basins in the same way that ships plow through the ocean.

false

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

arc

Intense geologic activity is concentrated at plate ______.

boundaries

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

boundaries

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

decompression

Island chains and seamounts cross parts of the ocean floor. These oceanic islands and associated seamounts are _____.

different in character and origin from curved island arcs. Curved island arcs are related to subduction.

The surface of Earth is notable for many geologic features including _____

dramatic mountains, undersea trenches, intricate coastlines, beautiful valleys

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

iron-rich minerals align with Earth's magnetic field

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

outer

The zigzag pattern of mid-ocean ridges reflects the alternation of the spreading segments with _______ faults.

transform

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

1: North America, South America, Europe, and Africa were all part of the same super-continent. 2. The crust underneath the super-continent 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 super-continent to form a narrow ocean basin. 5. The ocean basin continued to widen through seafloor spreading.

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

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

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

A: Divergent B: Convergent C: Transform

Which of the following statements are accurate about what happens when two oceanic plates converge?

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

Which tools can be used to directly measure plate motion?

GPS satellites, lasers

Geologists fit together the southern continents into the supercontinent _____.

Gondwana

Which of the following does not describe continental rifting?

If rifting continues, the continent will remain intact.

_____ covers 71% of Earth's Surface

Oceans

The following are characteristics of slab pull:

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

Which of the following statements are true about characteristic geologic features with respect to their locations on Earth?

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

Which pieces of evidence supported Wegener's hypothesis of continental drift?

Southern continental landmasses seem to fit together like puzzle pieces. 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. Similar rocks and geologic structures exist in South America, Africa, and Antarctica. Glacial evidence exists in places that are now close to the equation, and the direction of glacial movement indicates the continents were once joined.

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

continental

Some continents continue outward from the shoreline under shallow seawater, forming submerged branches called _____

continental shelves

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

continents

Large volcanoes of the Andes Mountains of South America and the Cascade region of Washington and Oregon are the results of oceanic-continental plate __________.

convergence

The convergence of two continental masses is known as a _____

convergence collision

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

convergent boundary

Scratch marks made on rocks in the southern continent by ancient _____ show that the continents were once connected around the South Pole and then moved apart by continental drift.

glaciers

Curving island chains across the seafloor that are mainly volcanic in origin are called _____

island arcs

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

lithospehre

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

plates, chains

For a plate to move, the driving forces must exceed the _____ forces.

resisting

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

subduction

The process of one plate sliding beneath another plate is called ______

subduction

Along the boundary of an oceanic-continental convergence,

the oceanic plate sub-ducts beneath the continental plate

Tectonics is the study of _____

the origin and arrangement of the broad structural features of Earth's surface

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

transform

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

volcanoes

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.

seafloor spreading

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

transform boundary

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

1, 3

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

1. Ascension of magma causes uplift on 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.

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

1. Midway is the oldest of the listed islands. 2. Kauai is closer to Kilauea than Midway. 3. Kauai is younger than Midway.

Which of the following are involved in the Mendocino triple junction?

1. Two different transform faults 2. A subduction zone

Math the geologic feature with its location along the Southern American plate boundary.

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

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?

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

_____________ ____________ 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.

Mantle convection

How may times did Earth's magnetic field switch in the last 10 million years?

Many --- more than 40 times.

Which of the following statements are accurate about volcano distributions on Earth?

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. Volcanism occurs along mid-ocean ridges.

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

Mid, Atlantic, Ridge

Math the boundary type with the colour it is represented by on the map.

Yellow: Divergent Red: Convergent Green: Transform

The Pacific Ring of Fire is formed by ______.

a string of volcanoes.

The yearly rate of tectonic plate movement is best measured in _____.

centimetres

Both the matching of _____ outlines and their geology help to support the theory of plate tectonics.

continent

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

fossil

Broad symmetrical ridges that cross ocean basins are called _____.

mid-ocean ridges