Chapter 8outline
-
Upload
jmchenry071 -
Category
Technology
-
view
1.795 -
download
0
Transcript of Chapter 8outline
![Page 1: Chapter 8outline](https://reader036.fdocuments.us/reader036/viewer/2022070313/554a1db7b4c9058c5d8b559d/html5/thumbnails/1.jpg)
Chapter 8
Earthquakes and the Earth’s Interior
![Page 2: Chapter 8outline](https://reader036.fdocuments.us/reader036/viewer/2022070313/554a1db7b4c9058c5d8b559d/html5/thumbnails/2.jpg)
Earthquakes
Each year there are more than 30,000 earthquakes world wide.Generally, ____ are considered major quakes
Why don’t we know all this is happening?
Most earthquakes occur in remote areas with little property damage.
![Page 3: Chapter 8outline](https://reader036.fdocuments.us/reader036/viewer/2022070313/554a1db7b4c9058c5d8b559d/html5/thumbnails/3.jpg)
An earthquakes is
the vibration of the Earth produced by a rapid release of energy.Earthquakes originate at a point in the Earth called the………..
_________Energy is release in all directions from the focus in the form of waves.
![Page 4: Chapter 8outline](https://reader036.fdocuments.us/reader036/viewer/2022070313/554a1db7b4c9058c5d8b559d/html5/thumbnails/4.jpg)
![Page 5: Chapter 8outline](https://reader036.fdocuments.us/reader036/viewer/2022070313/554a1db7b4c9058c5d8b559d/html5/thumbnails/5.jpg)
The _________ is the location on the surface directly above the focus.
![Page 6: Chapter 8outline](https://reader036.fdocuments.us/reader036/viewer/2022070313/554a1db7b4c9058c5d8b559d/html5/thumbnails/6.jpg)
Faults
The earth is under constant change. It is pressed, pulled, uplifted, etc…Fractures in the crust where actual movement has occurred is called a….
________
![Page 7: Chapter 8outline](https://reader036.fdocuments.us/reader036/viewer/2022070313/554a1db7b4c9058c5d8b559d/html5/thumbnails/7.jpg)
![Page 8: Chapter 8outline](https://reader036.fdocuments.us/reader036/viewer/2022070313/554a1db7b4c9058c5d8b559d/html5/thumbnails/8.jpg)
Case Study: San Andreas
1906 – San FranciscoDuring this single event, the land on the western side of the fault shifted as much as 4.7 meters to the north when compared to the eastern side.
![Page 9: Chapter 8outline](https://reader036.fdocuments.us/reader036/viewer/2022070313/554a1db7b4c9058c5d8b559d/html5/thumbnails/9.jpg)
What causes earthquakes?Forces within the earth deform the rocks.These forces cause the rocks to bend and store _________________Eventually, this elastic energy is overcome and released at the….
_______Slippage and buildup of energy along the fault can continue until that energy is released. Rocks then snap back in place.
![Page 10: Chapter 8outline](https://reader036.fdocuments.us/reader036/viewer/2022070313/554a1db7b4c9058c5d8b559d/html5/thumbnails/10.jpg)
Elastic Rebound Theory
The spring back of the rocks into their original place is called the…
__________________
![Page 11: Chapter 8outline](https://reader036.fdocuments.us/reader036/viewer/2022070313/554a1db7b4c9058c5d8b559d/html5/thumbnails/11.jpg)
![Page 12: Chapter 8outline](https://reader036.fdocuments.us/reader036/viewer/2022070313/554a1db7b4c9058c5d8b559d/html5/thumbnails/12.jpg)
Most earthquakes are produced by the rapid release of elastic energy stored in rock that has been subjected to great forces. When the strength of the rock is ___________, it suddenly breaks, causing the __________ of an earthquake.
![Page 13: Chapter 8outline](https://reader036.fdocuments.us/reader036/viewer/2022070313/554a1db7b4c9058c5d8b559d/html5/thumbnails/13.jpg)
Aftershocks and Foreshocks
Earthquakes do not last very long.The 1906, San Francisco quake lasted 40 seconds.The movements that follow a major earthquake often produce smaller earthquakes called….
______________These aftershocks are usually less intense
or weaker than the main quake.
![Page 14: Chapter 8outline](https://reader036.fdocuments.us/reader036/viewer/2022070313/554a1db7b4c9058c5d8b559d/html5/thumbnails/14.jpg)
Small earthquakes that often occur before a major earthquake are called…..
___________They may occur days or years before a
major event.Please Note: Faults are not just one crack
in the crust. They may have numerous tributary faults much like a stream pattern.
![Page 15: Chapter 8outline](https://reader036.fdocuments.us/reader036/viewer/2022070313/554a1db7b4c9058c5d8b559d/html5/thumbnails/15.jpg)
Measuring Earthquakes
The study of seismology goes back at least 2,000 years to the ________.
![Page 16: Chapter 8outline](https://reader036.fdocuments.us/reader036/viewer/2022070313/554a1db7b4c9058c5d8b559d/html5/thumbnails/16.jpg)
Seismographs
Are instruments that record earthquake waves.
How do they work?
![Page 17: Chapter 8outline](https://reader036.fdocuments.us/reader036/viewer/2022070313/554a1db7b4c9058c5d8b559d/html5/thumbnails/17.jpg)
Weight suspended from a support attached to bedrock.
bedrock
bedrock
Earth moves
Drum records motion
Weight does not move with ground motion due to inertiav
Weight hinged to allow movement
![Page 18: Chapter 8outline](https://reader036.fdocuments.us/reader036/viewer/2022070313/554a1db7b4c9058c5d8b559d/html5/thumbnails/18.jpg)
Seismogram
This is an amplified electronic record of ground motion, producing a trace (graph) called a ____________.
![Page 19: Chapter 8outline](https://reader036.fdocuments.us/reader036/viewer/2022070313/554a1db7b4c9058c5d8b559d/html5/thumbnails/19.jpg)
Earthquake Waves
Earthquake waves spread out in all directions from the….
________.The seismogram shows these waves
in two forms1. ______________2. ______________
![Page 20: Chapter 8outline](https://reader036.fdocuments.us/reader036/viewer/2022070313/554a1db7b4c9058c5d8b559d/html5/thumbnails/20.jpg)
Surface waves
Body waves
![Page 21: Chapter 8outline](https://reader036.fdocuments.us/reader036/viewer/2022070313/554a1db7b4c9058c5d8b559d/html5/thumbnails/21.jpg)
Surface Waves
Are the seismic waves that travel along Earth’s outer layer (or ____________). These waves actually cause the ground to move.Surface waves are much like waves in the ocean moving up and down as well as side to side.These are the _____________ earthquake waves.
![Page 22: Chapter 8outline](https://reader036.fdocuments.us/reader036/viewer/2022070313/554a1db7b4c9058c5d8b559d/html5/thumbnails/22.jpg)
Body WavesThese waves travel the Earth’s interior.
There are two types:1. ___________: Primary waves, these waves
compress (push) and expand (pull) rocks in the direction the waves travel.
2. ___________: Secondary waves, shakes the particles at right angles to their direction of travel. Gases and liquids will not transmit s-waves.
![Page 23: Chapter 8outline](https://reader036.fdocuments.us/reader036/viewer/2022070313/554a1db7b4c9058c5d8b559d/html5/thumbnails/23.jpg)
![Page 24: Chapter 8outline](https://reader036.fdocuments.us/reader036/viewer/2022070313/554a1db7b4c9058c5d8b559d/html5/thumbnails/24.jpg)
![Page 25: Chapter 8outline](https://reader036.fdocuments.us/reader036/viewer/2022070313/554a1db7b4c9058c5d8b559d/html5/thumbnails/25.jpg)
Locating an Earthquake
The difference in velocities of P and S waves provides a way to locate the epicenter.P waves always reach a seismograph before S wave. The greater the interval measured on a seismogram between the arrival of the first P wave and the first S wave, the greater the distance to the earthquake source.
![Page 26: Chapter 8outline](https://reader036.fdocuments.us/reader036/viewer/2022070313/554a1db7b4c9058c5d8b559d/html5/thumbnails/26.jpg)
Earthquake DistanceTravel time graphs are
constructed from seismograms.First, find the time interval between the arrival of the first P wave and the first S wave on the seismogram.Find, on the time travel graph the equivalent time spread between the P and S wave curve.From this information, you can see the distance is 3,800 km. From the seismograph.
![Page 27: Chapter 8outline](https://reader036.fdocuments.us/reader036/viewer/2022070313/554a1db7b4c9058c5d8b559d/html5/thumbnails/27.jpg)
Earthquake Direction
We must recognize that the epicenter could be in any direction from our station. We draw a circle around our location on a map using the information from the time-travel graph.We then contact at least two (or more) stations and obtain their time travel data and draw circles around their stations.Where the _____________ intersect is the location of the earthquake’s _____________.
![Page 28: Chapter 8outline](https://reader036.fdocuments.us/reader036/viewer/2022070313/554a1db7b4c9058c5d8b559d/html5/thumbnails/28.jpg)
Triangulation
![Page 29: Chapter 8outline](https://reader036.fdocuments.us/reader036/viewer/2022070313/554a1db7b4c9058c5d8b559d/html5/thumbnails/29.jpg)
Seismic Wave SpeedsSeismographs at
five observation stations recorded the arrival times of the P and S waves produced by an earthquake. These data are shown in the graph.
![Page 30: Chapter 8outline](https://reader036.fdocuments.us/reader036/viewer/2022070313/554a1db7b4c9058c5d8b559d/html5/thumbnails/30.jpg)
Seismic Wave Speeds
X-axis––distance from the epicenter; y-axis––arrival time.
Reading Graphs:
What variable is shown on the x-axis of the graph? The y-axis?
![Page 31: Chapter 8outline](https://reader036.fdocuments.us/reader036/viewer/2022070313/554a1db7b4c9058c5d8b559d/html5/thumbnails/31.jpg)
Seismic Wave Speeds
7 minutes
Reading Graphs:
How long did it take the S waves to travel 2,000 km?
![Page 32: Chapter 8outline](https://reader036.fdocuments.us/reader036/viewer/2022070313/554a1db7b4c9058c5d8b559d/html5/thumbnails/32.jpg)
Seismic Wave Speeds
4 minutes
Estimating:
How long did it take the P waves to travel 2,000 km?
![Page 33: Chapter 8outline](https://reader036.fdocuments.us/reader036/viewer/2022070313/554a1db7b4c9058c5d8b559d/html5/thumbnails/33.jpg)
Seismic Wave Speeds
2,000 = 3.5 minutes4,000 = 4.5 minutes
Calculating:
What is the difference in the arrival times of the P waves and the S waves at 2,000 km? At 4,000 km?
![Page 34: Chapter 8outline](https://reader036.fdocuments.us/reader036/viewer/2022070313/554a1db7b4c9058c5d8b559d/html5/thumbnails/34.jpg)
Locating the Epicenter
![Page 35: Chapter 8outline](https://reader036.fdocuments.us/reader036/viewer/2022070313/554a1db7b4c9058c5d8b559d/html5/thumbnails/35.jpg)
Earthquake Zones
About 95% of the major earthquakes occur in a few narrow zones.Most fall on the _______________Another active zone is along the Mediterranean Sea.A third belt coincides with the mid-ocean ridge system.
![Page 36: Chapter 8outline](https://reader036.fdocuments.us/reader036/viewer/2022070313/554a1db7b4c9058c5d8b559d/html5/thumbnails/36.jpg)
![Page 37: Chapter 8outline](https://reader036.fdocuments.us/reader036/viewer/2022070313/554a1db7b4c9058c5d8b559d/html5/thumbnails/37.jpg)
Measuring EarthquakesScientists have used two different measurements to describe the size of an earthquake – intensity and magnitude._________ is the amount of shaking at a given location based on earthquake damage. _____________ are quantitative measurements that rely on calculations using seismographs. Magnitudes are a measure of the size of seismic waves or the amount of energy released at the source of the earthquake.
![Page 38: Chapter 8outline](https://reader036.fdocuments.us/reader036/viewer/2022070313/554a1db7b4c9058c5d8b559d/html5/thumbnails/38.jpg)
Richter Scale
This is an outdated method of measuring the magnitude of an earthquake. The Richter scale is based on the ____________________________ (P,S, or surface wave) recorded on a seismogram. A ________________ in wave amplitude equals an increase of 1 on the magnitude scale.
![Page 39: Chapter 8outline](https://reader036.fdocuments.us/reader036/viewer/2022070313/554a1db7b4c9058c5d8b559d/html5/thumbnails/39.jpg)
Example: An earthquake with a magnitude of 5.0 is ___________ greater than an earthquake with a magnitude of 4.0. Since earthquake waves weaken with distance, The Richter scale is only useful for small, shallow earthquakes within 500 km of the epicenter. ______________ use the Richter scale, but scientists no longer use it.
![Page 40: Chapter 8outline](https://reader036.fdocuments.us/reader036/viewer/2022070313/554a1db7b4c9058c5d8b559d/html5/thumbnails/40.jpg)
Moment Magnitude
________________ is derived from the amount of displacement that occurs along a fault zoneFactors used to calculate the Moment Magnitude:
1. ______________________2. ______________________3. ______________________
![Page 41: Chapter 8outline](https://reader036.fdocuments.us/reader036/viewer/2022070313/554a1db7b4c9058c5d8b559d/html5/thumbnails/41.jpg)
(surface area of fault) X ( average displacement along fault) X (rigidity of rock)
These factors together provide a
measure of ____________________ rock can store before it suddenly slips and releases its energy during an earthquake.
![Page 42: Chapter 8outline](https://reader036.fdocuments.us/reader036/viewer/2022070313/554a1db7b4c9058c5d8b559d/html5/thumbnails/42.jpg)
Moment magnitude is the _______________________ measurement for earthquakes because it is the only magnitude scale the estimates the energy released by earthquakes.
![Page 43: Chapter 8outline](https://reader036.fdocuments.us/reader036/viewer/2022070313/554a1db7b4c9058c5d8b559d/html5/thumbnails/43.jpg)
![Page 44: Chapter 8outline](https://reader036.fdocuments.us/reader036/viewer/2022070313/554a1db7b4c9058c5d8b559d/html5/thumbnails/44.jpg)
![Page 45: Chapter 8outline](https://reader036.fdocuments.us/reader036/viewer/2022070313/554a1db7b4c9058c5d8b559d/html5/thumbnails/45.jpg)
Destruction from Earthquakes Good Friday, 1964, AlaskaThis is the scene of the most violent earthquake in North America during the 20th century. The moment magnitude was 9.2 and the event lasted 3-4 minutes. The quake left 131 dead and thousands homeless. The state’s economy was badly damaged. However, if this quake had happened on an average weekday, many more lives would have been lost.
![Page 46: Chapter 8outline](https://reader036.fdocuments.us/reader036/viewer/2022070313/554a1db7b4c9058c5d8b559d/html5/thumbnails/46.jpg)
Seismic Vibrations
The damage to buildings and other structures from earthquake waves depends on several factors:1. ___________________________2. ______________________ on which the structure is built3. ____________ of the structure
![Page 47: Chapter 8outline](https://reader036.fdocuments.us/reader036/viewer/2022070313/554a1db7b4c9058c5d8b559d/html5/thumbnails/47.jpg)
Building Design
What type of building would best survive an earthquake?
__________________Why?
They are more _________
![Page 48: Chapter 8outline](https://reader036.fdocuments.us/reader036/viewer/2022070313/554a1db7b4c9058c5d8b559d/html5/thumbnails/48.jpg)
Multi-story buildings suffer the most. Steel reinforced buildings survive the best. Many new construction techniques place hydraulics and springs under buildings to allow more movement. The frequency of earthquake vibrations has much to do with which buildings are damaged.
![Page 49: Chapter 8outline](https://reader036.fdocuments.us/reader036/viewer/2022070313/554a1db7b4c9058c5d8b559d/html5/thumbnails/49.jpg)
Liquefaction
Where loosely consolidated sediments are saturated with water, earthquakes can cause a process call ______________. Under these conditions normally stable soil turns to liquid that is not able to support a buildings. Structures may settle or collapse. Underground storage tanks and sewer lines may float toward the surface.
![Page 50: Chapter 8outline](https://reader036.fdocuments.us/reader036/viewer/2022070313/554a1db7b4c9058c5d8b559d/html5/thumbnails/50.jpg)
Tsunamis
are destructive ocean waves.
![Page 51: Chapter 8outline](https://reader036.fdocuments.us/reader036/viewer/2022070313/554a1db7b4c9058c5d8b559d/html5/thumbnails/51.jpg)
Causes of Tsunamis
A tsunami triggered by an earthquake occurs where a slab of the __________________________ vertically along a fault. A tsunamis can also occur when the vibration of a quake sets an underwater landslide into motion.
![Page 52: Chapter 8outline](https://reader036.fdocuments.us/reader036/viewer/2022070313/554a1db7b4c9058c5d8b559d/html5/thumbnails/52.jpg)
A tsunami travels across the ocean at speeds of 500 to 950 kilometers per hour. In the open ocean a tsunami can pass unnoticed. How is this possible?
Its height is usually less than 1 meter and the distance between wave crests can range from 100 to 700 kilometers.When the tsunami enters shallower coastal water, the waves are slowed and the water begins to pile up to heights that’s sometimes are greater than 30 meters.
![Page 53: Chapter 8outline](https://reader036.fdocuments.us/reader036/viewer/2022070313/554a1db7b4c9058c5d8b559d/html5/thumbnails/53.jpg)
![Page 54: Chapter 8outline](https://reader036.fdocuments.us/reader036/viewer/2022070313/554a1db7b4c9058c5d8b559d/html5/thumbnails/54.jpg)
Tsunami Warning System
Large earthquakes are reported to the Tsunami Warning System in Honolulu from seismic stations around the Pacific. Scientists use water levels in tidal gauges to determine whether a tsunami has formed. A warning is then issued so evacuation of coastlines near the epicenter can proceed.On average, only one or two tsunamis are generated each year. Only about one tsunamis in every 10 years causes major damage and loss of life.
![Page 55: Chapter 8outline](https://reader036.fdocuments.us/reader036/viewer/2022070313/554a1db7b4c9058c5d8b559d/html5/thumbnails/55.jpg)
Other Dangers
________________ – unconsolidated rock and soil on slopes loosen and fall because of earthquake vibrations. They can also cause ground to collapse, liquefy, or subside.
![Page 56: Chapter 8outline](https://reader036.fdocuments.us/reader036/viewer/2022070313/554a1db7b4c9058c5d8b559d/html5/thumbnails/56.jpg)
__________ – 1906, San Francisco…..many wood structures burned when gas and electric lines where cut. Many water lines were broken crippling firefighters. In 1923, an earthquake in Japan caused an estimated 250 fires. These fires destroyed half of Tokyo and killed over 100,000 people.
![Page 57: Chapter 8outline](https://reader036.fdocuments.us/reader036/viewer/2022070313/554a1db7b4c9058c5d8b559d/html5/thumbnails/57.jpg)
Predicting Earthquakes
________________ Predictions – The goal of short-range predictions are to provide an early warning of the location and magnitude of a large earthquake.
![Page 58: Chapter 8outline](https://reader036.fdocuments.us/reader036/viewer/2022070313/554a1db7b4c9058c5d8b559d/html5/thumbnails/58.jpg)
Researchers monitor precursors:1. __________2. __________3. __________4. __________5. __________
Short range predictions have not been successful.
![Page 59: Chapter 8outline](https://reader036.fdocuments.us/reader036/viewer/2022070313/554a1db7b4c9058c5d8b559d/html5/thumbnails/59.jpg)
Long-Range Predictions
These forecasts give the probability of certain magnitude earthquakes occurring within 30 – 100+ years.
Predictions are based on the idea that earthquakes are repetitive or cyclic. Scientists study historical records looking for patterns of occurrence. They also study, seismic gaps, which are areas along faults where there has not been any earthquake activity for a long period of time.
![Page 60: Chapter 8outline](https://reader036.fdocuments.us/reader036/viewer/2022070313/554a1db7b4c9058c5d8b559d/html5/thumbnails/60.jpg)
There has only been __________in long-term forecasting. Scientists just don’t yet understand enough to about earthquakes to make accurate predictions.
![Page 61: Chapter 8outline](https://reader036.fdocuments.us/reader036/viewer/2022070313/554a1db7b4c9058c5d8b559d/html5/thumbnails/61.jpg)
Earth’s Layered Structure
How can we study the internal structure of the Earth? Lets come up with some ideas…….
__________
![Page 62: Chapter 8outline](https://reader036.fdocuments.us/reader036/viewer/2022070313/554a1db7b4c9058c5d8b559d/html5/thumbnails/62.jpg)
Layers Defined by Composition
If the Earth were made of the same materials throughout, seismic waves would……?Spread through it in a straight lines at constant speed.
![Page 63: Chapter 8outline](https://reader036.fdocuments.us/reader036/viewer/2022070313/554a1db7b4c9058c5d8b559d/html5/thumbnails/63.jpg)
![Page 64: Chapter 8outline](https://reader036.fdocuments.us/reader036/viewer/2022070313/554a1db7b4c9058c5d8b559d/html5/thumbnails/64.jpg)
What we know……
Seismic waves reaching seismographs located farther from the earthquake travel at faster average speeds than those recorded at locations closer to the event. Seismic increase in speed with depth is due to increased pressure.As a result, seismic waves are __________ as they travel.
![Page 65: Chapter 8outline](https://reader036.fdocuments.us/reader036/viewer/2022070313/554a1db7b4c9058c5d8b559d/html5/thumbnails/65.jpg)
![Page 66: Chapter 8outline](https://reader036.fdocuments.us/reader036/viewer/2022070313/554a1db7b4c9058c5d8b559d/html5/thumbnails/66.jpg)
Earth’s interior consists of three major zones defined by its chemical composition – __________, __________, and __________.
![Page 67: Chapter 8outline](https://reader036.fdocuments.us/reader036/viewer/2022070313/554a1db7b4c9058c5d8b559d/html5/thumbnails/67.jpg)
CrustThe crust is the thin, rocky outer layer of the Earth. It is divided into the oceanic and continental crust. __________– composed of mostly basaltic (basalt) rock averaging 7 km thick. __________– 8-75 km thick and is composed mostly of granitic (granite) rock.
Oceanic rocks are generally younger than continental rocks and __________.
![Page 68: Chapter 8outline](https://reader036.fdocuments.us/reader036/viewer/2022070313/554a1db7b4c9058c5d8b559d/html5/thumbnails/68.jpg)
lithosphere
asthenosphere
mantle
![Page 69: Chapter 8outline](https://reader036.fdocuments.us/reader036/viewer/2022070313/554a1db7b4c9058c5d8b559d/html5/thumbnails/69.jpg)
Mantle
Over 82% of the Earth’s volume is contained in the mantle. The mantle is a rocky solid with __________properties. Rocks here are composed of mostly peridotite and denser than the crust.
![Page 70: Chapter 8outline](https://reader036.fdocuments.us/reader036/viewer/2022070313/554a1db7b4c9058c5d8b559d/html5/thumbnails/70.jpg)
Core
Composed of an __________alloy. The core is the most dense layer about 13 times denser than water.
![Page 71: Chapter 8outline](https://reader036.fdocuments.us/reader036/viewer/2022070313/554a1db7b4c9058c5d8b559d/html5/thumbnails/71.jpg)
![Page 72: Chapter 8outline](https://reader036.fdocuments.us/reader036/viewer/2022070313/554a1db7b4c9058c5d8b559d/html5/thumbnails/72.jpg)
Layers Defined by Physical Properties
Earth’s interior gradually increases in __________, __________, and __________ with depth.
![Page 73: Chapter 8outline](https://reader036.fdocuments.us/reader036/viewer/2022070313/554a1db7b4c9058c5d8b559d/html5/thumbnails/73.jpg)
__________– when a substance is heated, the transfer of energy increases the vibration of the particles. If the temperature exceeds the melting point, the forces between the particles are overcome and melting begins.If temperature were the only factor that determined whether a substance melted, the Earth would be a molten ball covered with a thin, solid outer shell.
![Page 74: Chapter 8outline](https://reader036.fdocuments.us/reader036/viewer/2022070313/554a1db7b4c9058c5d8b559d/html5/thumbnails/74.jpg)
As temperature increases with depth, so does pressure which increases rock strength. This can cause a substance to become brittle, putty-like, or liquid.
Earth can be divided into layers based on physical properties – __________, __________, __________, and __________.
![Page 75: Chapter 8outline](https://reader036.fdocuments.us/reader036/viewer/2022070313/554a1db7b4c9058c5d8b559d/html5/thumbnails/75.jpg)
Lithosphere and Asthenosphere
__________ – crust (both oceanic and continental) and the uppermost mantle. __________ – under the lithosphere, it is slightly weaker than the crust. Its temperature and pressure results in a small amount of melting. Rocks here are close enough to their melting point and therefore __________.
![Page 76: Chapter 8outline](https://reader036.fdocuments.us/reader036/viewer/2022070313/554a1db7b4c9058c5d8b559d/html5/thumbnails/76.jpg)
Lower Mantle – The lower mantle is more rigid than the upper mantle. Rocks here are very hot and capable of flow (much like molten plastic). Rocks at the edge of the outer core are softer and more flowing.
![Page 77: Chapter 8outline](https://reader036.fdocuments.us/reader036/viewer/2022070313/554a1db7b4c9058c5d8b559d/html5/thumbnails/77.jpg)
Inner and Outer Core
__________– a liquid layer __________– Despite its high temperature, the material in the inner core is compressed into a solid state by the immense pressure.
![Page 78: Chapter 8outline](https://reader036.fdocuments.us/reader036/viewer/2022070313/554a1db7b4c9058c5d8b559d/html5/thumbnails/78.jpg)
So, how does the Earth generate its magnetic field?
The outer core rotates at a different speed then does the inner core and the mantle. __________ is created __________. This in turn is our gravity.
![Page 79: Chapter 8outline](https://reader036.fdocuments.us/reader036/viewer/2022070313/554a1db7b4c9058c5d8b559d/html5/thumbnails/79.jpg)
Discovering Earth’s Layers
In 1909, a Croatian seismologist discovered that the velocity of seismic waves increases abruptly below 50 kilometers of depth. This boundary separates the crust from the underlying mantle and is known as the Mohorovicic discontinuity or __________.
![Page 80: Chapter 8outline](https://reader036.fdocuments.us/reader036/viewer/2022070313/554a1db7b4c9058c5d8b559d/html5/thumbnails/80.jpg)
![Page 81: Chapter 8outline](https://reader036.fdocuments.us/reader036/viewer/2022070313/554a1db7b4c9058c5d8b559d/html5/thumbnails/81.jpg)
Another boundary was found between the mantle and the outer core. P waves are bent around the outer core. The outer core causes P waves that travel through the core to arrive several minutes later than expected. This region is called the __________.
![Page 82: Chapter 8outline](https://reader036.fdocuments.us/reader036/viewer/2022070313/554a1db7b4c9058c5d8b559d/html5/thumbnails/82.jpg)
Shadow zone
![Page 83: Chapter 8outline](https://reader036.fdocuments.us/reader036/viewer/2022070313/554a1db7b4c9058c5d8b559d/html5/thumbnails/83.jpg)
S waves do not travel through the outer core; therefore geologists concluded that this region is __________.
![Page 84: Chapter 8outline](https://reader036.fdocuments.us/reader036/viewer/2022070313/554a1db7b4c9058c5d8b559d/html5/thumbnails/84.jpg)
Discovering Earth’s Composition
1. __________through drilling in the continental crust. Mostly granite2. __________– Mostly basalt3. __________– practically melted asthenosphere yields peridotite, which is a lava like material in Hawaii. 4. __________ show us a peridotite substance as well as iron-nickel.
![Page 85: Chapter 8outline](https://reader036.fdocuments.us/reader036/viewer/2022070313/554a1db7b4c9058c5d8b559d/html5/thumbnails/85.jpg)
Earth’s inner core is like the iron-nickel meteorites The mantle is like the peridotite meteorites.Time to think about the description in chapter 1 of how the Earth formed. Do you remember?