L2 Plate Tectonics (Chapter 2)

Seafloor ___ provide the basis for reconstructing plate motions for about the last 200 million years.

isochrons

According to the theory of plate tectonics, the Earth's __ is broken into over a dozen moving plates. The plates slide over a hot and weak __, and the continents, embedded in some of the moving plates, are carried along.

lithosphere; asthenosphere

During the Ocean-Continent Convergence, the __ plate is going to subduct. What you will see is a __ arc form above the point of subduction on the ___.

oceanic; volcanic; continent

Which of the following is created by TRANSFORM plate movement? Mid-Atlantic Ridge Gulf of California Seamounts Japanese islands Peru-Chile Trench Volcanic Arc Himalayas Offset of creek beds San Andreas Fault

Offset of creek beds San Andreas Fault

Magnetic anomaly

One in a pattern of long, narrow bands of high or low magnetic intensity on the seafloor that are parallel to and almost perfectly symmetrical with respect to the crest of a mid-ocean ridge

Ocean-ocean convergent boundary

One plate subducts beneath the other, producing a long, narrow deep-sea trench, and an island arc is produced behind the trench

Wegener's hypothesis

Proposed continental drift in 1915

Magnetic time scale

The detailed history of Earth's magnetic field reversals as determined by measuring the thermoremanent magnetization of rock samples whose ages are known

Continental drift

The large-scale movements of continents across Earth's surface driven by the plate tectonic system

Seafloor spreading

The mechanism by which new oceanic crust is formed at a spreading center on the crest of a mid-ocean ridge. As two plates move apart, magma wells up into the rift between them to form new crust, which spreads laterally away from the rift and is replaced continually by newer crust

What caused the end of Pangaea?

the continental rift

Convergent boundary

A boundary between lithospheric plates where the plates move toward each other and one plate is recycled into the mantle.

Trench

A long, narrow depression in the ground or seafloor.

Divergent boundary

A boundary between lithospheric plates where two plates move apart and new lithosphere is created.

Island arc

A chain of volcanic islands formed on the overriding plate at a convergent boundary by magma that rises from the mantle as water released from the subducting lithosphere slab causes fluid-induced melting

Isochron

A contour that connects rocks of equal age define contour: an outline bounding the shape of something

Spreading center

A divergent boundary, marked by a rift at the crest of a mid-ocean ridge, where new oceanic crust is formed by seafloor spreading

Transform boundary

A plate boundary at which the plates slide horizontally past each other and lithosphere is neither created nor destroyed

Pangaea

A supercontinent that coalesced in the late Paleozoic era and comprised all present continents, then began to break up in the Mesozoic era

The _____ is an example of a divergent plate margin. A. East African Rift B. Japan Trench C. Himalayas D. San Andreas fault

A. East African Rift

The ______ are an example of a collision zone between twopieces of continental crust riding on converging lithospheric plates. A. Himalaya Mountains B. islands of Japan C. Aleutian Islands in Alaska D. Andes Mountains in South America

A. Himalaya Mountains

Where do the plate-driving forces originate? A. Tectonic plates are passively dragged by convection currents. B. Gravity pulls and/or pushes old, cold, heavy lithosphere. C. Injection of magma from the mantle pushes the lithosphere apart. D. Earthquakes cause the plates to move.

A. Tectonic plates are passively dragged by convection currents.

Which of the following features is not associated with a type of active plate boundary? A. Atlantic coast of North America B. northwestern North America C. Gulf of California D. Himalayas

A. The Atlantic coast of North America is a passive continental margin, which is not associated with an active plate margin.

The most important process in building the ocean floor is A. volcanism B. subduction C. earthquake activity D. magnetic reversal

A. Volcanism at the oceanic ridges builds the seafloor.

The youngest ocean crust is located A. along the oceanic ridges. B. in the oceanic trenches. C. around hot spots. D. on the abyssal seafloor.

A. along the oceanic ridges.

Volcanic island arcs like the Japanese islands are associated with A. convergent boundaries. B. divergent boundaries. C. transform boundaries. D. a chain of hot spots.

A. convergent boundaries.

The significance of the magnetic anomaly patterns discovered in association with the seafloor was that the anomaly patterns A. could be matched with the magnetic reversal chronology to establish an estimated age for the seafloor. B. provided evidence for mantle convection, a driving mechanism for plate tectonics. C. allowed geomagnetists to reconstruct the supercontinent Rodinia. D. represented absolute proof that the seafloor was spreading apart.

A. could be matched with the magnetic reversal chronology to establish an estimated age for the seafloor.

Magnetic anomalies in the seafloor are caused by A. magnetic reversals recorded by lavas erupted at oceanic spreading centers. B. changes in the atomic structure of minerals in response to changing ocean depth. C. the metamorphism of deep-sea sediments. D. the heating up of subducting oceanic lithosphere as it plunges deeper into the mantle

A. magnetic reversals recorded by lavas erupted at oceanic spreading centers.

Ring of Fire

An area where a large number of earthquakes and volcanic eruptions occur in the basin of the Pacific Ocean

Mid-ocean ridge

An undersea mountain chain at a divergent boundary, characterized by earthquakes, volcanism, and rifting, all caused by the tensional forces of mantle convection that are pulling the two plates apart

The oldest rocks on the seafloor are about A. 20 million years old. B. 200 million years old. C. 500 million years old. D. 1 billion years old.

B. 200 million years old.

Mid-ocean ridges, according to the plate tectonic theory, are A. places where oceanic crust is consumed. B. pull-apart zones where new oceanic crust is produced. C. locations of plate convergence. D. transform faults.

B. Mid-oceanic ridges or spreading centers are divergent boundaries where the crust is extending (pulling apart) and magma seeps through the asthenosphere to form new ocean floor.

The oceanic crust A. becomes progressively younger away from the oceanic ridges. B. becomes progressively older away from the oceanic ridges. C. is the same age virtually everywhere. D. ranges in age from Jurassic to Precambrian.

B. becomes progressively older away from the oceanic ridges.

Rates of seafloor spreading today are in A. millimeters per year. B. centimeters per year. C. meters per year. D. kilometers per year.

B. centimeters per year.

Rift valleys are associated with A. convergent boundaries. B. divergent boundaries. C. transform boundaries. D. active continental margins.

B. divergent boundaries.

How can the age of the seafloor and its relative plate velocity be determined?

By using magnetic anomalies to detect changes in the paleo-magnetic properties of the ocean floor.

All the following features mark plate boundaries except A. the Red Sea. B. the San Andreas fault. C. the Hawaiian Islands. D. Iceland.

C. The Hawaiian islands formed over a hot spot in the middle of the Pacific ocean plate.

At which type of plate boundaries are volcanoes least likely to form? A. divergent boundaries B. convergent boundaries C. transform boundaries D. hot spots

C. Volcanism is not characteristic of transform plate boundaries.

With what tectonic activity is a rift valley usually associated? A. subduction B. movement on a transform fault C. continental rupture D. continental collision

C. continental rupture

During the early Triassic (237 Ma), A. India collided with Asia to form the Himalayan Mountains. B. the supercontinent Rodinia formed. C. the supercontinent Pangaea was mostly assembled. D. the Atlantic Ocean had already begun to open

C. the supercontinent Pangaea was mostly assembled.

Continent-continent convergent boundary

Continent-continent convergence produces a double thickness of crust, which results in high mountain ranges (ex. Himalayas)

Mountain range

Continent-continent convergence produces a double thickness of crust, which results in high mountain ranges (ex. Himalayas)

__ crust is less dense than _ crust.

Continental; oceanic

What drives plate tectonics?

Convection, the force of gravity, and the existence of an asthenosphere are all important factors in any explanation of plate movement.

The name given to the supercontinent that broke up in the Early Jurassic (195 Ma) was A. India. B. Atlantis. C. Laurasia. D. Pangaea.

D. Pangaea began to break up during the Jurassic Period.

Earth's lithosphere can be characterized as A. having an average thickness of about 100 km. B. including the crust and upper mantle. C. being solid and above the asthenosphere. D. all of the above.

D. all of the above.

South America lay closest to the South Pole during the A. late Proterozoic (650 Ma). B. last 65 million years. C. late Jurassic (152 Ma). D. early Devonian (390 Ma).

D. early Devonian (390 Ma).

Along a transform plate boundary, the two plates A. move apart to create a widening rift valley. B. are being consumed by subduction. C. are being forced together to produce a mountain system. D. move horizontally past each other.

D. move horizontally past each other.

Subduction Zones are to ___ margins while Mid-ocean Ridges are to ____ margins.

Destructive; Constructive

Which of the following lithospheric plate movements include the presence of Volcanoes? Divergent Convergent (Ocean to Ocean) Convergent (Ocean to Contin.) Convergent (Contin. to Contin.) Transform

Divergent Convergent (Ocean to Ocean) Convergent (Ocean to Contin.)

What are the 3 features that matched on continents now separated by the Atlantic Ocean?

Fossils Rock types/ages Similar Geological Structures Glacial Deposits

What is the theory of plate tectonics?

It describes the movement of lithospheric plates and the forces acting between them. It also explains the distribution of many large-scale features that result from movements at plate boundaries: mountain chains, earthquakes, volcanoes, topography of the seafloor, and distribution of rock assemblages and fossils.

Which of the following is created by CONVERGENT plate movement? Mid-Atlantic Ridge Gulf of California Seamounts Japanese islands Peru-Chile Trench Volcanic Arc Himalayas Offset of creek beds San Andreas Fault

Japanese islands Peru-Chile Trench Volcanic Arc Himalayas

Which of the following is created by DIVERGENT plate movement? Mid-Atlantic Ridge Gulf of California Seamounts Japanese islands Peru-Chile Trench Volcanic Arc Himalayas Offset of creek beds San Andreas Fault

Mid-Atlantic Ridge Gulf of California Seamounts

__ typically form along convergent and transform plate boundaries. Where divergent plate boundaries are exposed on land, subsiding basins and __ are typical

Mountains; volcanoes

Ocean-continent convergent boundary

Oceanic plate subducts beneath the continental plate. A mountain range is produced parallel to the deep-sea trench. Earthquakes are produced along the subduction zone and volcanoes appear in the mountain belt behind the trench

Subduction

The sinking of oceanic lithosphere beneath overriding oceanic or continental lithosphere at a convergent plate boundary

Plate tectonics

The theory that describes and explains the creation and destruction of Earth's lithospheric plates and their movement over Earth's surface

How is the history of plate movement reconstructed?

Transform boundaries indicate the directions of relative plate movement, and seafloor isochrons reveal the positions of divergent boundaries in earlier times.

What are some of the geologic characteristics of plate boundaries? (It is important to visualize each major type of plate boundary and their locations on Earth.)

Volcanoes and earthquake activity are concentrated along plate boundaries. Where divergent plate boundaries are exposed on land, subsiding basins and volcanism are typical. Mountain chains form along convergent and transform plate boundaries.

Earth's internal heat creates _ currents (flow of rock material from hotter to cooler areas) in the mantle.

convective

Convection is generated within the Earth's mantel because of ___ heating (which creates density differences); __ (a force created by density differences); __.

differential; buoyancy; gravity

What are the 3 major boundaries between lithospheric plates?

divergent boundaries: where plates move apart; convergent boundaries: where plates move together and one plate often subducts beneath the other; transform boundaries: where plates slide past each other.

Some geologists believe in Pangaea because of geological similarities in __ evidence and the distribution of __ deposits as well as other paleo-climatic evidence.

fossil; glacier

Transform boundaries indicate the directions of _ plate movement, and seafloor isochrons reveal the positions of _ boundaries in earlier times.

relative; divergent

When 2 ocean crusts are converging one is going to __. What you will see is a __ above the point of __.

subduct; volcano; subducting