chapter 18 physical science

Seismological studies suggest that the core

has a liquid outer core and solid inner core.

Evidence that Earth’s magnetic field has undergone numerous reversals can be found

in the orientation of iron minerals that cooled in once molten rock.

The middle part of Earth’s interior is

mantle

Most of Earth’s mass is contained in the

mantle

A vibration that moves through any part of Earth is called a

seismic wave.

Which of the following statements about Earth’s core is true?

The core is mostly made of iron.

What is the current theory about why the plates move?

Convective cells move from the core to the lithosphere.

Records of the strength and directions of Earth’s magnetic field are found in

igneous rocks.

Deep core drilling provides most of the evidence for the nature of Earth’s interior.

False

The oldest rocks are found in

continental crust.

From the study of ancient compasses, it has become apparent that Earth’s magnetic polarity reverses every 2,000 years

False

The crust beneath the oceans is much older than continental crust.

False

Japan is a group of arc islands associated with

the convergence of two oceanic plates.

The current estimate for the age of Earth is about ____ years.

4.6 billion

Studies of the Mid-Atlantic Ridge provided evidence to support this.

seafloor spreading.

Earth’s crustal layer is

all of the answers are correct.

The spreading of the sea floor along the Mid-Atlantic ridge is supported by

all of these ideas support the sea-floor-spreading hypothesis

he least dense rocks in Earth are found in

the continental crust

The presence of an oceanic trench, a chain of volcanic mountains along the edge of a continent, and deep-seated

earthquakes is characteristic of

ocean-continent plate convergence

Earth formed layers because

heavy elements sank to lower levels and lighter ones rose while Earth was still molten

When an oceanic plate and continental plate converge,

the oceanic plate is subducted beneath the continental plate.

According to the plate tectonics theory, sea-floor spreading occurs at a

divergent boundary.

The crust is a thin layer of granite rock that makes up the continents and ocean basins.

false

the core of Earth is composed of

iron and nickel

Hot, molten rock moves up from Earth’s core, causing the continents to drift apart.

false

The mantle is largely composed of ferromagnesian minerals such as olivine.

true

The mantle is composed of

silicates

Seismic waves show a sudden increase at the Mohorovičić discontinuity because the

composition of minerals on both sides of the layer is different.

Earth’s magnetic field seems to reverse its polarity about every

2000 years

The interior of Earth is molten from the heat produced by the intense bombardment Earth experienced during its formation.

False

What caused Earth to melt during Earth’s early formation?

radioactive decay

The chain of mountains found in the center of the Atlantic Ocean basin is called the

Mid-Atlantic Ridge

The plate boundary associated with the formation of new crust is called

divergent

The Himalayan Mountains were formed as a result of

continent-continent plate collision

According to plate tectonics, new crustal material is created at

divergent plate boundaries.

The layer that is broken up into plates that move in the upper mantle is called the

lithosphere.

The asthenosphere is

a plastic layer in which the lithosphere is embedded

The Hawaiian Islands were formed as

the Pacific plate moved over a hot spot.

The three main areas of Earth’s interior are

core, mantle, and crust.

The San Andreas Fault is the site of a

transform boundary.

The separation of materials that gave Earth is layered interior is called

differentiation.

Evidence from meteorite studies suggests that the core is composed of

nickel and iron.

The S-wave is a

transverse wave.

The Mohorovičić discontinuity separates the mantle from the outer core

False

Geologists observe that oceanic crust is different from continental crust because

seismic waves travel at different speeds through these materials.

S-waves from earthquakes travel through both solid and liquid, but P-waves cannot travel through liquid.

False

Long, deep, and narrow oceanic trenches are located

parallel to the edges of continents.

Long, high, and continuous mountain ranges run through the middle of the oceans.

True

The driving force behind the movement of oceanic and continental plates is most likely

convection cells within the mantle.