Chapter 22 Tectonic Plates

What is a plume?

a zone of upwelling material originating at the outer core-mantle boundary

The hypothesis of continental drift was supported by the jigsaw fit of the continents, similar _______.

fossils, matching rock types, and ancient ice sheets

The core of Earth is probably composed of

iron and nickel

Outer core

the liquid layer of the Earth's core that lies beneath the mantle and surrounds the inner core

According to the theory of seafloor spreading, large quantities of molten rock rises up along

the mid-ocean ridges.

Midocean ridge

A global system of underwater mountains created by seafloor spreading

Plate Tectonics

A theory stating that the earth's surface is broken into plates that move.

Which of the following mountain ranges are examples of continental arcs?

Andes and Cascades

Ocean Trench

Deep valley in the ocean floor that forms along a subduction zone

Lower mantle

One of Earths structural layers---the lowest portion of the mantle, a zone of strong, rigid rock.

Asthenosphere

One of earths structural layers-----a layer of weak, warm rock that flows slowly over geologic time.

Inner core

One of the Earth's structural layers---a solid sphere of hot metal, most iron, at the center of the earth.

Transform boundaries

Places where tectonic plates slide along beside one another as they move

How do plates move at divergent plate boundaries?

Plates move apart.

What is the relationship between the crust and lithosphere?

The crust is part of the lithosphere.

Differentiation

The process by which earth formed layers according to density

Subduction

The process by which oceanic crust sinks beneath a deep-ocean trench and back into the mantle at a convergent plate boundary.

Seafloor spreading

The process that creates new sea floor as plates move away from each other at the mid-ocean ridges

Subduction zone

The region where oceanic plates sink down into the asthenosphere.

Earthquake

The shacking of the ground that results when rock under Earth's surface moves or breaks.

Earth Science

The study of history, structure, and natural processes of planet earth

Mantle

The thick layer of dense, hot rock between Earth's crust and core.

Why do we say that Earth science is an integrated science?

Earth science encompasses a broad spectrum of natural science disciplines, including physics, chemistry, biology, and astronomy.

What features at the surface provide evidence of plumes?

Hot spots

What is the relationship between temperature and density?

In general, warmer materials are less dense, and colder materials are denser.

Tectonic plates

Large movable plates under the Earth's surface.

Magma

Molten rock beneath the earth's surface

Why are volcanoes NOT found at transform boundaries?

Transform boundaries do not cause changes to the pressure, temperature, or composition of the mantle.

What is convection?

a cycle of moving material formed by the rise of less-dense material and the sinking of denser material

What is a volcanic arc?

a row of volcanoes that forms on the overriding plate near a subduction zone

Transform faults are areas of crustal

accommodation and plate movement

Convergent boundaries are

all of the above

Where is the youngest ocean floor found?

along the crest of mid-ocean ridges

The East African rift is a divergent plate boundary that is splitting the continent of Africa into two pieces. What will eventually form around this divergent boundary?

an ocean

The mantle can be separated into two different portions-the lower mantle and the upper mantle. The lower mantle is

completely solid due to extreme pressure that prevents rocks from melting.

Continental crust extends farther down into the mantle than oceanic crust because

continental crust is thicker than oceanic crust.

Divergent boundaries are areas of

crustal formation.

Which of the following terms best characterizes upwelling in the asthenosphere?

diffuse

In general, where do earthquakes AND volcanic eruptions occur?

divergent plate boundaries convergent plate boundaries

Plates move apart at __________ boundaries, move together at __________ boundaries, and move side-by-side at __________ boundaries.

divergent/convergent/transform

Alfred Wegener supported his theory of continental drift by

making a connection between the rocks, rock structures, and plant and animal fossils found in both Africa and South America.

Which geologic features are associated with divergent boundaries?

mid-ocean ridges and continental rift valleys

What forms at divergent plate boundaries?

new oceanic lithosphere

Which geologic features are associated with convergent boundaries?

ocean trenches and volcanoes

The two elements that make up about 75% of Earth's crust are__________ and________.

silicon and carbon

Isostasy is

the positioning of the crust in response to the buoyant force and gravity. (equilibrium)

What would happen to Earth if ocean floor were created at divergent boundaries at a faster rate than it is destroyed at convergent boundaries?

The Earth would increase in volume.

What accounts for most tectonic plate motion?

forces at subduction zones

Seafloor spreading provides the mechanism for continental drift, because at the spreading center _______.

formation of new lithosphere pushes the continents

Because S-waves do not travel through Earth's outer core, scientists inferred that the outer core is

molten liquid.

Complete this statement: Divergence is to moving away as convergence is to _______.

moving toward

The three kinds of plate convergence are

oceanic-oceanic continental-oceanic continental-continental

In general, where do volcanoes form in subduction zones?

on the overriding plate, away form the convergent boundary

The theory of seafloor spreading is supported by

paleomagnetic analysis of the ocean's floor.

Convergent boundaries

place where two plates come together

How do plates move at transform plate boundaries?

plates move side by side

How do plates move at convergent plate boundaries?

plates move toward one another

The inner core is solid because

pressure from the weight of the surrounding layers prevents the inner core from melting

P-waves refract at the boundary between inner and outer core because

there is a change of phase between inner and outer core

The theory of plate tectonics states that the continents move because _______.

they are embedded within the drifting lithospheric plates.

Lithosphere

Earth's outermost structural layer, consisting of cool, rigid rock

Crust

Earth's surface layer, consisting of oceanic and continental crust

Core

Earths innermost layer, which is mostly iron and includes the inner core and outer core

Divergent boundaries

Places where plates are pulling apart

Continental drift

The hypothesis that the continents slowly move across Earth's surface.

Oceanic and continental crust differ in that

All of the above.

Geology

The Earth science that is concerned with the composition and structure of the Earth.

Seismology

The study of earthquakes