Download Dynamic Crust Part 2

Earthquake Waves
There are three types of earthquake waves.
1.
P-Waves
a. Travel the fastest
b. Primary
c. Push-Pull
d. Compression waves
2. S-Waves
a. Travel less slowly
b. Secondary
c. Side-to-Side
d. Cause more damage
3. Surface Waves
a. Travel along Earth’s surface
b. Include both push-pull & side-to-side motion
c. Cause most damage
Locating an Epicenter
Seismograph records magnitude of an earthquake
Seismologists use the difference in speed of P-waves and S-Waves
As time difference between P & S-waves increase the distance from
the epicenter increases
To find the epicenter data from at least three different recording
stations must be used
Seismologists draw a circle around the station using a radius equal
to the distance from the epicenter
Where the three circle intersect is the epicenter
Origin Time:
The origin time is when the earthquake occurred at the epicenter
Origin time can be found using
Time difference between P-waves and S-waves
Distance from epicenter
Use ESRT p. 11
Vocabulary p. 72-74
Asthenosphere: part of Earth’s interior below the lithosphere that becomes plastic
In response to stress
Basaltic: igneous rock composed mostly of dark-colored, dense minerals containing
Compounds of iron and magnesium (mafic)
Continental Crust: rocks within the continents, usually a thin layer of sedimentary rocks over
granitic rocks, that are less dense than oceanic crust
Core: innermost layer of Earth, thought to be composed mostly of iron and nickel
Crust: thin, outermost layer of the solid Earth
Granitic: rocks composed mostly of light-colored, low-density minerals such as quartz and feldspar
Inner Core: central portion of Earth’s core thought to be composed mostly of solid iron and nickel
Mantle: Portion of Earth below the crust and above the core
Moho: interface between Earth’s crust and mantle
Oceanic Crust: relatively thin, dense layer of basaltic rock that lies under the ocean sediments and
On top of the mantle layer
Outer Core: outside portion of Earth’s core thought to consist mostly of liquid iron and nickel
Earth’s Layers
Crust
Outermost layer
5-60 km deep
Two layers
1-Thin layer of sediments
2-Either
Continental Crust
Granitic
Less dense
Oceanic Crust
Basaltic
More dense
Darker colored
Mantle
Moho –boundary between crust and mantle
About 2900 km deep
Includes most of Earth’s volume
Earthquake waves travel faster here
Thought to be composed mostly of dense, dark, mafic minerals olivine and pyroxene
Two sections
1-Athenosphere
“Plastic”
Partially melted
More flexible
2-“Stiffer” Mantle
Core
Deepest layers of Earth
Thought to be composed mostly of iron with smaller amounts of nickel
Most dense layer
Two sections
1-Outer Core
Liquid
S-Waves cannot pass through
2- Inner Core
Solid (due to higher pressure)
Allows both P & S-waves to pass through
Earthquake Shadow Zones
See p. 74 in RB