Earth Science Exam 1 Study Flashcards Set 2 Plate Tectonics

The rate of plate motions affects global climate by affecting the amount of ____ gases, such as CO2, that may be either released into the atmosphere or consumed by the process.

greenhouse

What layer of Earth is composed of the crust and the uppermost mantle?

lithosphere

Oceanic trenches are narrow, deep, and found ____.

next to continents and next to volcanic island arcs

In general, tall mountains are ____ (in age) compared to shorter mountains.

younger

The contracting Earth model hypothesis was used by early scientists to explain the different features on Earth's surface. Which of the following were parts of this possible explanation?

All features on Earth are approximately the same age, ocean basins are formed due to surface collapse, and mountain belts result from the Earth cooling and contracting over time.

What is slab pull, and where does it occur?

An inward force that occurs at subduction zones

What is a ridge push, and where does it occur?

An outward force that occurs at oceanic ridges (causes the plates to move apart)

List the different features on continents that would match up if Pangaea were reassembled.

Animal and Plant fossils, Mountain belts, and Rock sequences

The ____ system is a long, continuous feature on the ocean floor that has a zipper-like appearance, is volcanic in origin, and is relatively shallow.

oceanic ridge

The creation of magma at ____ occurs due to decompression; the hot, less-dense magma rises and creates new ocean crust.

oceanic ridges

In order to achieve a balance in the size of the Earth, new lithosphere is created at ____ and destroyed at ____.

oceanic ridges; subduction zones

The Hawaiian Islands are progressively ____ (in age) with distance from the current location of the hot spot.

older

The geographic location of the African plate:

over Africa, and west into the Atlantic Ocean and east into the Indian Ocean

The ring of Fire describes the active volcanoes located around the edge of the ____ Ocean.

Pacific

Consider that the oldest rocks in both the Atlantic and Pacific are 180 million years old, yet the Pacific is much wider than the Atlantic. What is the direct cause for the size difference?

Plate motion associated with the Pacific is more rapid.

Wegener's continental drift theory was not accepted primarily because he did not have a mechanism to move continents across ocean basins. How did seafloor spreading provide this mechanism?

Seafloor spreading explained the movement of ocean crust to be like a conveyor belt, which also involved the movement of the adjoining continents.

What are some characteristics of active margins?

The west coast of North America is an example, This area is characterized by volcanoes and earthquakes, and The continental margin is also a plate boundary

The geographic location of the North American plate:

over North America and east into the Atlantic Ocean; also extends over much of the upper Northern Hemisphere

The geographic location of the Pacific plate:

over the Pacific Ocean

The geographic location of the Nazca plate:

over the southwestern Pacific, west of South America

A fundamental change in our understanding of a basic concept is called a ____ shift.

paradigm

What are some possible reasons why other planets in the solar system do not have plate tectonics?

They are too small and do not have enough internal heat and They have a very thick lithosphere that hinders plate motion.

What is the physical relationship between the geographic and magnetic north poles?

They are usually in different places, as the magnetic pole does move.

Where is the thickest continental crust on Earth's surface found?

Where continental collision occurs.

When the lithosphere breaks apart and a rift valley is formed, magma is created through the ____.

process of decompression

When the lithosphere breaks apart, it forms a ____ valley.

rift

A new divergent boundary begins by ____.

breaking apart a continent

A hot spot on Earth's surface is created ____.

by a mantle plume

**Describe the birth and development of a divergent boundary by putting the sentences in the correct order, with the earliest step on top.

1. Continental lithosphere begins to break apart 2. A rift valley forms and eventually widens 3. New ocean floor is created and seawater flows in to create a new, narrow ocean 4. The narrow ocean widens and matures over millions of years

Paleomagnetism is the study of Earth's magnetic field as preserved in rocks. How are changes in the magnetic field preserved in rocks?

Magnetic minerals within the rocks align themselves parallel to the field.

What geographic location represents a rift valley?

East Africa

True or False: Continental drift was widely accepted soon after it was introduced in the early 1900s.

False

True or false: All tectonic plates move at the same rate.

False

True or false: Plate shape and boundaries remain constant over time.

False

True or false: Transform plate boundaries occur only within continental crust.

False

How does paleomagnetism support the seafloor spreading theory?

Known ages of reversals of the magnetic field preserved in continental rocks were correlated with reversal patterns found on the ocean floor.

Which of the following provide evidence used by Wegener to support his continental drift theory?

Similar fossils on separate continents, Paleoclimate data, The apparent "puzzle piece" fit of the continents, and Similar mountain belts on separate continents.

Which of the following describes oceanic trenches?

Some are found next to continents and they are long and deep.

Plates horizontally slide past each other at ____ boundaries.

conservative

What is Pangaea?

A supercontinent that began to break apart 200 to 250 million years ago. It is a super-continent, made up of a northern group of continents and a southern group of continents.

Which of the following correctly describe the timing of magnetic field reversals?

The average reversal lasts for 250,000 years, and The longest reversal lasted 37 million years.

Which is older: oceanic crust or the continents?

The continents are older.

How does the depth of the ocean floor change from a continental shelf to an oceanic ridge?

The depth to water is shallow, then is deep, and then shallow again.

What does the pattern of colors representing the age of ocean crust on either side of the Mid-Atlantic Ridge demonstrate?

The youngest ocean crust is next to the ridge, and gets successively older to the west and east.

How does the existence of ancient glacial deposits in India, Australia, South America, and southern Africa support continental drift?

They suggest that the continents were together and were located closer to a pole about 300 million years ago.

What ocean floor feature marks the process of subduction?

Trench, but volcanoes can be formed by processes other than subduction

True or false: The same pattern of magnetic reversals recorded in the ocean crust is found in all of Earth's major oceans.

True

What describes the process of magma formation at subduction zones?

Water released from the subducted oceanic lithosphere moves into the overlying plate and induces it to melt.

Alfred ____ was the first person to develop and publish a sound explanation for the origin of the continents and oceans.

Wegener

Why did most scientists not agree with the continental drift theory?

Wegener was not a well-known scientist, he used deductive reasoning, which was not the norm at the time, and he could not provide a sound explanation for how the continents moved.

A continental margin that coincides with a plate boundary is called ____, whereas a continental margin that is not a plate boundary is called ____.

active; passive

Tectonic plates move ____.

at different yet steady rates (These rates range from less than 1 cm/yr to over 15 cm/yr)

Melting occurs when ____. This can occur due to a rise in temperature, or because of a drop in pressure.

bonds between molecules are broken

Plate tectonic theory is based on the premises introduced by Wegener's ____ drift.

continental

When looking at a modern map showing continents defined by their coastlines, it is easy to imagine them fitted together like pieces of a puzzle as suggested by continental drift. However, the fit is even better as defined by their ____ shelves.

continental

The historic idea called ____ ____ says that the Earth once had a supercontinent named Pangaea that has broken up and moved over time.

continental drift

The process of ____ within Earth's mantle transfers heat energy from the core to the surface and drives plate motion.

convection

The contracting Earth model was used to explain Earth's different features as resulting from the Earth ____ over time

cooling and shrinking

The heat within Earth's ____ is transferred to the surface and is the driving force for the movement of lithospheric plates.

core

The Earth's magnetic poles ____.

dance around a bit, and occasionally reverse

Lithosphere that can be subducted is ____.

denser than the crust it encounters, older than the crust it encounters if the density is the same, and is oceanic crust

Large amounts of data concerning the ocean floor were first collected ____.

during World War II

The frequency of ____ decreases with depth at subduction zones because the lithosphere warms up and loses its brittleness.

earthquakes

The asthenosphere flows like a liquid ____.

even though it is a solid

True or false: The Hawaiian Islands are formed at a plate boundary.

false

The Hawaiian Islands are created as the ____ ____ remains stationary and the Pacific plate moves over the top of it.

hot spot

What has to occur in order to melt a rock?

increasing temperature, decreasing pressure (on hot rocks), and chemical reactions following the addition of water

Plate tectonic theory explains that large-scale geologic processes such as earthquakes and volcanoes result directly and primarily from ____.

interactions at plate boundaries

The San Andreas Fault ____.

is in California, is a transform plate boundary, and is found between a divergent and a convergent boundary

Even though they had no evidence of such a feature, scientists who contradicted continental drift suggested that the same fossils in Africa and South America were explained by a ____ ____ existing across the ocean.

land bridge

The Earth's ____ is divided into ____ tectonic plates.

lithosphere; eight major and a few smaller

The oceanic ridge system has a relatively high heat flow resulting from the eruption of ____ onto the seafloor.

magma

Divergent plate boundaries are created where hot rock rises from the ____.

mantle

The asthenosphere is the weak layer in the upper ____ that underlies the rigid lithosphere.

mantle

Plate tectonics affects climate in many ways. Examples include how the alignment of the continents determines patterns of ____ current circulation, and that large continents over the poles reduce solar radiation, resulting in global ____.

ocean; cooling

The geographic location of the Eurasian plate:

over Asia and Europe, including Indonesia, and the northeastern Atlantic

The Red Sea has formed due to the ____ of East Africa.

rifting

The ____ ____ theory explains that new oceanic lithosphere is formed along oceanic ridges; the seafloor here is elevated due to the magma, and then sinks in elevation as it continuously moves away from the ridge.

seafloor spreading

The Wadati-Benioff zone ____ at oceanic trenches.

shows how earthquakes increase in depth with distance along an inclined plane

Magnetic polarity reversals recorded in ocean floor rocks reveal a symmetrical ____ pattern on either side of oceanic ridges.

striped

Patterns in magnetic polarity changes recorded in the ocean crust can be compared to patterns recognized in similar rocks on land in order to determine ____.

the age of the ocean crust

Inclination is:

the angle a magnetic (compass) needle makes with a horizontal plane

Declination is:

the angle between the geographic North Pole and the magnetic north pole

What is the name of the feature on the ocean floor that indicates subduction is occurring?

trench

Which of the following are linked to the process of subduction?

trench and convergent boundary

Most active volcanoes are located adjacent to oceanic ____, while most earthquakes are found near both oceanic trenches and ____.

trenches, ridges

Scientists originally calculated the rate of plate movement by ____.

using the age of seafloor rock and its distance from an ocean ridge

The southern continents of the supercontinent Pangaea are known as ____, and the northern continents are known as ____.

Gondwana, Laurasia

How did Harry Hess collect the data he needed to come up with the idea of seafloor spreading?

He was the captain of a ship equipped with sonar during World War II.

What is the source of energy that drives Earth's lithospheric plates to move?

Heat flow from Earth's interior

Describe the formation of magma at subduction zones by putting the events in the correct order, with the first event on top.

1. Oceanic lithosphere is pulled downward at a trench 2. The descending plate releases water 3. Partial melting occurs due to the addition of water in the mantle above the subducting plate 4. Magma rises to the surface to form volcanoes, or cools and solidifies within the crust

At the oceanic-continental convergent plate boundary:

Subduction produces a chain of volcanoes on the continent. Ex. Andes Mountains

At the oceanic-oceanic convergent plate boundary:

Subduction produces a volcanic island arc. Ex. Aleutian Islands