Geology Chapter 3: Plate Tectonics

Which of the following are characteristics of continental rifting?

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

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

-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

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

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

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

-Similar rocks and geologic structures exist in South America, Africa, and Antarctica -glacial evidence exists in places that are now close to the equator, and the direction of glacial movement indicates the continents were once joined -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

Characteristics of slab pull

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

Select areas on Earth that represent convergent boundaries

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

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

-ocean trenches and associated island arcs have numerous earthquakes -there are few earthquakes on the abyssal plains -earthquakes are common along the western coasts of North and South America

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

-temperatures increase within the subduction zone, releasing water, which induces melting -one of the two oceanic plates subducts beneath the other plate -an oceanic trench is formed and sediments begin to collect -buoyant magma rises into the overlying plate

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

-two different transform fault -a subduction zone

Volcanic distributions on Earth

-volcanism occurs along mid-ocean ridges -there is a large volcanic belt along the west coasts of North and South America -many volcanoes along the edge of the Pacific Ocean are associated with earthquakes

Plates move ______ per year

1 to 15 cm

The Stages of Continental Rifting

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 a seafloor spreading takes place 4. Continuation of seafloor spreading increases the ocean basins as it becomes wider

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

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 continues to widen through seafloor spreading

Select the five oceans of earth from the list below

Arctic Ocean Atlantic Ocean Indian Ocean Pacific Ocean Southern Ocean

_______ patterns develop on the seafloor as iron-rich minerals in newly erupted basaltic basaltic lava align with Earth's magnetic poles

Magnetic

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

Subduction of both sides of the _______ Ocean produces the Ring of Fire

Pacific

Volcanoes that extend from the southwestern Pacific Ocean, through the Phillippine Islands, Japan, and Alaska, then down the western coasts of the Americas form the Pacific ______ of fire

Ring

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

San Andreas

The process of plate tectonics circulates materials between the asthenosphere and the lithosphere

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

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

They are different ages, so they have different cooling histories

Regions of the deep ocean characterized by smooth ocean floor are called ________

abyssal plains

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.

age

Seamount

an eroded volcanic island beneath the sea surface

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

arcs

The surface of Earth is notable for many geologic features including___________.

beautiful valleys dramatic mountains undersea trenches intricate coastlines

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

boundaries

When two continental masses converge, it is refereed to as a continental _________

collision

When divergent boundaries occur on continents, the process is called ________

continental

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

curves and abrupt bends that appear in boundaries between plates

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

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

Mantle convection involves the asthenosphere moving upward due to its lower __________.

density

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

A transform fault on the ocean floor that is no longer active creates a step in seafloor elevation called a __________ zone.

fracture

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

glaciers

Ridge push involves _________

gravity causing the plate to slide away from the topographically high ridge, pushing the plate outward

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

heat

The type of plate movement that occurs at transform faults is __________.

horizontal

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

hot spots

an accretionary prism of sediments and oceanic crust is formed _____________

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

The majority of transform boundaries are located ________.

in conjunction with mid-ocean ridges

Plate boundaries are where most of Earth's ________ occurs.

intense geologic activity

When two oceanic plates converge, some magma erupts under the ocean, forming volcanoes that may rise above the sea. These volcanoes form a curved __________.

island arc

Tectonic settings of eastern side

lack of tectonic activity wide continental shelf passive margin

Which tools can be used to directly measure plate motion?

lasers and GPS satellites

Tectonic plates are composed of _______ and move around on top of the asthenosphere

lithosphere

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

mountains

Tectonic settings of western side

mountains trench subduction zone

Enormous mountain belts and high plateaus are formed when two continental plates collide as ___________.

neither is subducted

Basalt forming today from cooling magma at the mid-ocean ridge would have ________ polarity

normal

Earth's magnetic field currently flows from south to north. We refer to this orientation as ____________ polarity

normal

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

ocean

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

oceanic fracture zones

The layer of Earth that behaves as a dynamo (electrical generator), producing the magnetic field, is the __________

outer core

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 at plate boundaries. An explanation for this is _____________.

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

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

At mid-ocean ridges as two plates diverge, ____________

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

The process of one plate sliding beneath another plate is

subduction

How is magma created in a subduction zone?

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

Along the boundary of an oceanic-continental convergence, ___________

the oceanic plate subducts 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(n) ________ fault

transform

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

transform

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

triple

Divergent Boundary

two plates move apart relative to one another (magma fills the space between the plates

Transform Boundary

two plates move horizontally past one another (white arrows on the top surface)

Convergent Boundary

two plates move toward one another (one plate slides under the other

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