Seismic Waves Lesson

ESS2.2 Standard Review
Earth's Layers and Seismic Waves

Vocabulary

Earthquake - a sudden and violent shaking of the ground, sometimes causing great destruction, as a result of movements within the earth's crust

Fault Line - an extended break in a body of rock, marked by the relative displacement and a discontinuity of strata on either side of a particular surface (where rock layers don’t match up because of an earthquake)
Epicenter - the point on earth's surface above where an earthquake occurred

Seismic Wave - a wave in the earth produced by an earthquake

Primary (P) Wave - a type of seismic wave that causes rock to vibrate in the direction of the wave; faster of the two seismic waves and can travel through solid and liquid portions of the earth (pressure wave)

Secondary (S) Wave - a type of seismic wave that causes rock to move at right angles (perpendicular) of the wave; second fastest of the seismic waves and can only travel through solid portions of the earth (shear wave)

Seismograph - an instrument that measures and records details of earthquakes, such as force and duration

Seismogram - a record of seismic activity produced by a seismograph
Triangulation - using three seismometers (seismographs) in order to locate the epicenter of an earthquake (by measuring the distance between each seismograph and the earthquake)

Crust - outermost hard solid layer of the earth

Mantle - hot dense region of earth’s interior between the crust and the core

Core - innermost layer of earth, mostly made of iron and nickel
Lithosphere - Outer layer of earth made of hard/rigid, solid rock (crust and tiny part of upper mantle; made up of tectonic plates)
Asthenosphere - Soft/Plastic, solid layer of the earth that makes up the upper mantle (where mantle convection occurs)
Mesosphere - Hard/Rigid, solid layer of earth that makes up the lower mantle
Outer Core - the outer liquid part of the core
Inner Core - the inner solid part of the core

Triangulating an Earthquake

Earthquakes originate underground and many of them are so weak that they can't be noticed by humans without a machine. Occasionally, even though they can't be detected by people, they can still cause damage to infrastructure. This means it's important to observe earthquake data to determine if cities need to look for places that need repairs. Geologists can determine an earthquakes position using triangulation, which requires three seismographs to pinpoint the origin/epicenter.

Multiple Choice

Which layer of the earth is liquid?

• Lithosphere

• Asthenosphere

• Outer Core

• Inner Core

Multiple Choice

How do scientists record seismic waves?

• Seismograph

• Relative Dating

• Sound Recorder

• Surveys

Multiple Choice

How many seismographs are needed to locate the epicenter of an earthquake?

• 1

• 2

• 3

• 4

Multiple Choice

Which of these statements correctly describes P-Waves and S-Waves?

• P-Waves are released first, then S-Waves. P-Waves can go through solids and liquids, while S-Waves can only go through solids.

• P-Waves and S-Waves are released at the same time. P-Waves are faster and can travel through liquids and solids, while S-Waves are slower and can only travel through solids.

• S-Waves are released first, then P-Waves. S-Waves can go through solids and liquids, while P-Waves can only go through solids.

• S-Waves and P-Waves are released at the same time. S-Waves are faster and can travel through liquids and solids, while P-Waves are slower and can only travel through solids.

Reorder

List the layers of the earth in order from the one closest to the surface to the one that's the deepest.

• Lithosphere

• Asthenosphere

• Mesosphere

• Outer Core

• Inner Core

1

2

3

4

5

• 1
• 2
• 3
• 4
• 5

Multiple Choice

The picture shows a cross section of half of the earth. If an earthquake were to happen at the location marked $$0\degree$$ , which of these locations would not register P-Waves or S-Waves?

• $$30\degree$$

• $$60\degree$$

• $$90\degree$$

• $$120\degree$$

Multiple Choice

The picture shows a cross section of half of the earth. If an earthquake were to happen at the location marked $$0\degree$$ , which of these locations would register P-Waves but not S-Waves?

• $$45\degree$$

• $$90\degree$$

• $$120\degree$$

• $$150\degree$$

Multiple Choice

What is the core of the earth mostly made of?

• Igneous Rock

• Metamorphic Rock

• Sedimentary Rock

• Iron and Nickel

Multiple Choice

What quality of earth's layers cause seismic waves to move faster as they get deeper into the earth?

• Layers become more dense

• Layers become less dense

• Layers become hotter

• Layers become colder

Multiple Choice

As seismic waves go through the earth they are ________, which is caused by their change in speed.

• reflected

• transmitted

• refracted

• diffracted