Lab 2: The Interior of the Earth

Key Q: What is the interior of the Earth like?

Part A: Observing Waves & Measuring Wave Speed

In our lab activity you learned that waves travel at a constant speed. Scientists cannot observe earthquake waves moving through the Earth in the same way you can observe waves moving through water. They can,

however, record and study the energy from the earthquake waves as the waves arrive at a recording

station (seismograph station). They can use information they record about

the waves to make models of the interior of the Earth.

Part A: Observing Waves & Measuring Wave Speed

Think about how what you studied relates to how scientists make models of the inside of the

Earth. What part of your experiment represented:

• Th earthquake releasing energy in the Earth?• The movement of energy waves from the

earthquakes (seismic waves) in the Earth?• The material in the Earth through which seismic

waves travel?• The arrival of a seismic wave at a seismograph

station where earthquakes are detected?

Part A: Observing Waves & Measuring Wave Speed

• Vibrations of the earths crust are earthquakes.• When an earthquake occurs energy waves

radiate out in all directions. These waves are called seismic waves.

• Scientist cannot see seismic waves traveling through the Earth but they can detect them with a seismograph.

• Seismologists, scientists that study earthquakes, can use the information they gather from studying these waves to make a conceptual model of the interior of the earth

Part B: Kinds of Seismic Waves• There are 3 kinds of seismic waves. Each

one travels at a constant speed and creates a different movement.

• Studying these waves can allow scientists to:– Determine the amount of energy released by

an earthquake (magnitude)– Determine the exact location of an earthquake– Create a model of the interior of the Earth.

Part B: Kinds of Seismic Waves• P-waves

– are the fastest moving waves.– Cause particles to move back and forth in

place.– Move through solids, liquids, and gases.

Part B: Kinds of Seismic Waves• S-waves

– Move slower than P-waves.– Cause particles in materials to move side to

side.– Travel only through solids.

Part B: Kinds of Seismic Waves• L-waves

– are the slowest moving waves.– Cause the surface to rise and fall like ocean

waves.– Cause the most damage.– Travel through solids liquids, and gases.

Which wave…• Travel through gases? • Travel through liquids? • Travel through solids? • Fastest waves?• Surface waves?• Slowest waves?• Cause particles to move back & forth in place?• Cause particles to move side to side? • Cause the most damage? • Cause surface to rise and fall like ocean waves?

Seismologists: scientists that study earthquakes

Seismic waves: earthquake waves

Seismograph: Instrument that detects seismic waves.

Fault: Fracture zone where rock has been movedFocus: area along the fault where movement first occursEpicenter: Point on the earths surface directly above the focus.

Calculate the epicenter & magnitude of an earthquake

http://www.sciencecourseware.org/virtualearthquake/vquakeexecute.html

Part C: Refraction of Waves

• We learned that waves travel at a constant speed when they travel through one kind of material.

• A waves speed depends on what material it is traveling through, so when the wave (P-wave) crosses a boundary line between 2 different materials in the Earth it REFRACTS.

Part C: Refraction of Waves

)20° (

Greater angle 60°

Boundary Line (between 2 layers of the Earth)

P-wavewave speed = 30cm/s

wave speed = 1m/s

Angle of wave in relation to the boundary line changed due to change in wave speed

REFRACTION: The change in direction of a wave due to its change in speed as it passes from one material to the next.

http://earthquake.usgs.gov/learn/animations/animation.php?

flash_title=Shadow+Zone&flash_file=shadowzone&flash_width=

220&flash_height=320• Annimation from usgs kids of shadow zones ADD IT!

Part D: Refraction of Earthquake Waves in the Earth

• P-waves– CAN travel through the whole planet.– Refract (change direction) at a boundary between the

different layers of the Earth– We know they refract because the refraction creates

shadow zones. (an area on the Earths surface where no seismic waves are received.)

• S-waves– Can NOT travel through the whole planet.– They can travel through the Crust & the Mantle but

STOP at the Outer Core because it is liquid & S-waves only travel through solids

Part D: Refraction of Earthquake Waves in the Earth

• Shadow Zones:– An area on the Earths surface where no

seismic waves are received.– Caused by the refraction of waves.– Shows that the earth has layers.

Layers of the Earth

Crust: cool layer of rigid rock

Lithosphere: rigid layer. Includes the Crust & the upper Mantle

Mantle: semi-rigid layer

Asthenosphere: Has plasticity (the ability to flow). lower portion of Mantle

Outer Core: liquid layer. S waves stop here.

Inner Core: solid