Why does continental crust stand higher on the mantlethan

How do P-waves travel through Earths interior? How do S-waves travel through Earths interior?

Can S-waves travel through liquids?.

Name the two types of surface waves, and describe the motion of each.

What was Andrija Mohorovicics major contribution to Earth science?

How did seismic waves contribute to the discovery of Earths core?

What is the evidence that Earths inner core is solid?

What is the evidence that Earths outer core is liquid?

In what ways are the asthenosphere and the lithosphere different from each other?

How does continental crust differ from oceanic crust?

Why does continental crust stand higher on the mantle than oceanic crust?

What key evidence did Alfred Wegener use to support his hypothesis of continental drift?

Wegener proposed that the worlds continents had at one time all been joined together into one supercontinent. What was the name of this supercontinent?

What role did paleomagnetism play in supporting the theory of continental drift?

Where are the deepest parts of the ocean?

What was the major discovery of Harry Hess?

How is the ocean floor similar to a gigantic, slow-moving tape recorder?

In what way does seafloor spreading support continental drift?

Name and describe the three types of plate boundaries.

The lithosphere moves because of convection currents in the mantle. What causes the convection currents?

What is a rift? Give an example.

What kind of boundary separates the South American Plate from the African Plate?

What are the three types of plate collisions that occur at convergent boundaries?

What is a transform boundary?

Are folded rocks primarily the result of compressional or tensional forces?

Distinguish between anticlines and synclines.

What is the difference between reverse faults and normal faults?

Which kind of fault forms primarily from tension in Earths crust? Primarily from compression?

What happens to rock when stress exceeds a rocks elastic limit?

Where are most of the worlds volcanoes formed?

What is the source of a tsunamis huge amount of energy?

A Slinky is a great example for seeing how seismic waves travel through Earths interior. Place the Slinky on the floor. With two people firmly holding the ends of the Slinky, stretch it out to about 5 ft in length (do not overstretch). On one end, pull the Slinky backward and then push forward rapidly. Stop, and observe. How do the coils move? Which type of seismic wave does this motion mimic? Once the Slinky has stopped moving, jerk the toy to the side so that it moves like a slithering snake. How do the coils move? Which type of seismic wave does this motion mimic?

Look for a very old window, and note the lens effect in the bottom part of the glass. Glass has both solid and liquid properties; in fact, it is often thought of as a very viscous liquid. Over many years, its downward flow due to gravity is evidenced by the increased thickness near the bottom of the pane. Tie this observation of plastic behavior into our discussion of plate tectonics. Which parts of Earth behave plastically? Which parts are rigid? What do these ideas have to do with plate tectonics?

As the ground shakes, so do buildings on top of the land. It is often said that earthquakes dont kill people, but falling buildings do. Older, unreinforced brick buildings and woodframe buildings can collapse during an earthquake. Reinforcing these older buildings helps to strengthen their structure. We can explore the strength of buildings by using five straws and some tape. Step 1: Make a square frame by taping four straws together. Hold the frame upright on a flat surface. Step 2: Hold the bottom straw in place with one hand. Push the top straw to the right with your other hand. Push as far as you can without breaking the frame. Step 3: Tape the fifth straw horizontally across the middle of the frame. Repeat Step 2. Step 4: Untape the fifth straw and retape it diagonally across the square from corner to corner. Repeat Step 2. Which frame is stronger: the four-straw or the five-straw frame? Why? How does the diagonal placement of the fifth straw affect the frames strength?

The weight of the ocean floor bearing down on the lithosphere is increased by the weight of ocean water. Relative to the weight of the 10-km-thick basaltic ocean crust (density 3 g/cm3), how much weight does a 3-km-deep ocean (density 1 g/cm3) contribute? Express your answer as a percentage of the crusts weight.

If the mid-Atlantic Ocean is spreading at 2.5 cm per year, how many years has it taken for it to reach its present width of about 5000 km?

The Richter magnitude scale is logarithmic, meaning that each increase of 1 point on the scale corresponds to an increase by a factor of 10 in the amplitude of the seismic waves recorded on a seismograph. An earthquake that measures magnitude 8 on the scale has how many times more ground-shaking effect than a quake that measures magnitude 6?

If you know the rate of movement along a fault, the amount of offset over a period of time can be calculated. The basic relationship is Rate = distance/time Movement along the San Andreas Fault is about 3.5 cm/yr. If a fence were built across the fault in 2005, how far apart will the two sections of the now-broken fence be in 2025?

The San Andreas Fault separates the northwest-moving Pacific Plate, on which Los Angeles sits, from the North American Plate, on which San Francisco sits. If the plates slide past each other at a rate of 3.5 cm/yr, how long will it take the two cities to form one large city? (The present distance between Los Angeles and San Francisco is 600 km.)

List the parts of Earths crust in order of generally increasing density: (a) oceanic crust, (b) continental crust, (c) asthenosphere, (d) lithosphere.

Going from slowest to fastest, rank the following seismic waves: (a) Rayleigh waves, (b) P-waves, (c) S-waves, (d) Love waves.

Earths crust and its core differ greatly in density. After a quick review of Sections 20.1 and 21.2, rank the following elements in order of increasing density: (a) iron, (b) silicon, (c) nickel, (d) aluminum.

Consult Figure 21.37 and rank these countries in terms of earthquake frequency (from greatest to least): (a) Greenland, (b) North America, (c) Indonesia, (d) Australia.

Earthquakes at plate boundaries vary in their size and destructiveness. Rank the types of plate boundaries according to increasing earthquake destructiveness: (a) divergent boundaries, (b) transform boundaries, (c) convergent boundaries.

Compare the relative speeds of primary and secondary seismic waves. Which type of material can each travel through?

How can seismic waves indicate whether regions inside Earth are solid or liquid?

How do seismic waves indicate layering of materials in Earths interior?

What is the evidence that Earths inner core is solid?

Speculate on why the lower part of the lithosphere is rigid and the asthenosphere is plastic, even though they are both part of the mantle.

Even though the inner and outer cores are both composed of predominantly iron and nickel, the inner core is solid and the outer core is liquid. Why?

What does the P-wave shadow tell us about Earths composition?

If Earths mantle is composed of rock, how can we say that the crust floats on the mantle?

Why is Earths crust thicker beneath a mountain range?

Which extends farther into the mantle: the continental crust or the oceanic crust? Why?

How do erosion and wearing away of a mountain affect the depth to which the crust extends into the lithosphere?

Describe how the different paths of polar wandering helped establish that continents move over geologic time.

Why are most earthquakes generated near plate boundaries?

What is the driving force for mountain building in the Andes?

At what type of plate boundary were the Appalachian Mountains produced?

Why do mountains tend to form in long narrow ranges?

What kind of plate boundary separates the North American Plate from the Pacific Plate?

Relate the formation of metamorphic rocks to plate tectonics. Would you expect to find metamorphic rocks at all three types of plate boundaries? Why or why not?

Why does granite form frequently at oceaniccontinental convergent boundaries but infrequently at oceanic oceanic convergent boundaries?

Cite one line of evidence that suggests that subduction once occurred off the coast of California.

Cite one line of evidence that suggests that subduction once occurred off the coast of California.

Are the present-day continents a permanent feature on our planet? Discuss why or why not.

Are the present-day continents a permanent feature on our planet? Discuss why or why not.

Why are the most ancient rocks found on the continents, not on the ocean floor?

Upon crystallization, certain minerals (the most important being magnetite) align themselves in the direction of the surrounding magnetic field, providing a magnetic fossil imprint. How does the seafloors magnetic record support the theory of continental drift?

How are the theories of seafloor spreading and continental drift supported by paleomagnetic data?

What kind of boundaries are associated with centers of seafloor spreading?

What is meant by magnetic pole reversals? What useful information do they tell us about Earths history?

How is Earths crust like a conveyor belt?

Where does most of an earthquakes damage generally occur?

What type of fault is associated with the 1964 earthquake in Alaska?

The Mercalli scale measures earthquake intensity. The Richter scale measures earthquake magnitude. Which scale is the more precise measurement? Why?

What is a very likely cause of the existence of Earths magnetic field?

Lithospheric rock is continuously created and destroyed. Where do the creation and destruction take place? Do the rates of the two processes balance each other?

Subduction is the process of one lithospheric plate descending beneath another. Why does the oceanic portion of the lithosphere undergo subduction while the continental portion does not?

How much more does the ground shake during a magnitude-6.6 earthquake than it does during a magnitude-5.6 earthquake?

In 1960, a large tsunami struck the Hawaiian Islands without warning, devastating the coastal town of Hilo. Since that time, a tsunami warning station has been established for the coastal areas of the Pacific. Why do you think these stations are located around the Pacific Rim?

How did the Himalaya Mountains originate? How did the Andes Mountains originate?

What is the direct source of energy responsible for earthquakes in southern California?

How do faults and folds support the idea that lithospheric plates move?

Reverse faults are created by compressional forces. Where in the United States do we find evidence of reverse faults?

Normal faults are created by tensional forces. Where in the United States do we find evidence of normal faults?

Strike-slip faults show horizontal motion. Where in the United States do we find strike-slip faulting?

If you found folded beds of sedimentary rock in the field, what detail would you need to know in order to tell whether the fold was an anticline or a syncline?

Does the fact that the mantle is beneath the crust necessarily mean that the mantle is denser than the crust? Explain.

Magma is generated at divergent and convergent plate boundaries. What type of magma is dominant at each boundary? Why are they different?

Where is Earths longest mountain range located?

How old is the Atlantic Ocean thought to be? For how many years has lava been extruding at the Mid-Atlantic Ridge?

What type of lava erupts at divergent boundaries? What type erupts at convergent boundaries?

In an earthquake, does the release of energy usually happen all at once? Defend your answer.

During an earthquake, what type of land surface is safer: rigid bedrock or sandy soil? Explain your thinking.

Where do most of the worlds earthquakes occur? Discuss features of various earthquakes in terms of: geologytype of plate boundary, fault, and rock type; and geographyeconomic development, preparedness, politics, and recovery efforts.

As global temperatures increase, the polar ice caps melt. What influence will this have on the isostatic balance of the lithosphere?

The FYI about the 2010 Chilean earthquake suggests that the quake caused a shift in Earths distribution of mass, which changed Earths rotation and resulted in a change in the day length. If Earths rotation increases, what is the effect on day length? If Earths rotation decreases, what is the effect on day length? In what other way can day length be affected?

What clues can we use to recognize the boundaries between ancient plates no longer in existence?

What geologic features are explained by plate tectonics?