Dynamic Earth Unit – Study Guide Physical Science Name _________________________
Define the following terms in your own words from the unit.
1. Crust – the outer and thinnest layer of the Earth
2. Mantle – the thickest layer of the Earth; beneath the crust
3. Inner core – the innermost layer of the Earth; composed of solid iron and nickel
4. Outer core – the layer between the inner core and mantle; made of liquid iron & nickel
5. Lithosphere – the crust and the uppermost mantle; solid, rigid rocky portion of Earth
6. Plate tectonics – theory that the Earth’s lithosphere is broken into plates which interact with one another
7. Subduction – the action of one plate descending beneath another; forms a trench
8. Asthenosphere – the pliable, plastic-like layer on which the lithospheric plates move
9. Seafloor spreading- theory that the ocean floor is spreading apart at mid-ocean ridges
10. Convergent plate boundary- when two tectonic plates collide with one another
11. Divergent plate boundary- when two tectonic plates pull apart from one another
12. Transform fault boundary- when two tectonic plates slide past one another
13. Paleomagnetism- “ancient” magnetism; recorded in seafloor rocks showing that the Earth’s magnetic
field has switched through time; shows mirror-image on either side of mid-ocean ridges indicating
seafloor spreading
14. Pangaea- supercontinent in Alfred Wegener’s hypothesis of Continental Drift
15. Tectonic plate – section of the lithosphere which carries both continent and ocean crust
16. Rift valley – valley produced from diverging plates
17. Convection- transfer of heat energy where a fluid is heated; causes material to rise when heated, sinks
when cools; produces a circulating current
18. Mid-ocean ridge – mountain chain that runs down the middle of ocean basins
19. Focus- the point of origin underground of an earthquake
20. Epicenter- the point on the surface directly above the earthquake’s focus
21. P-wave- a seismic wave, the first to reach a site, fastest wave, travels through both solids and liquids
22. S-wave – 2nd seismic wave to reach a site, causes majority of damage, travels through solids only
23. Tephra- solid material from an erupting volcano such as ash, cinders, bombs
24. Viscosity- a fluid’s resistance to flow
25. Pyroclastic- solid material from an erupting volcano
26. Shield volcano- largest volcano, made from lava layers, like the Hawaiian volcanoes
27. Cinder cone volcano- smallest volcano, made from tephra layers, like Sunset Crater
28. Composite volcano- most explosive volcano, made from both lava & tephra layers, like Mt. St. Helens
29. Hot spot – abnormally hot area in the mantle from which magma rises and breaks
through the crust to form volcanoes; like Hawaii & Yellowstone
30. Lahar – volcanic mudflow
Answer the following questions.
1. Who is credited with the hypothesis of Continental Drift? Alfred Wegener
2. Explain the concept of Continental Drift (not Plate Tectonics!). 200 million years ago, All the
continents of the world were together as one supercontinent, called Pangaea, and separated/moved to
their present-day locations
3. What evidence did this scientist show in favor of Continental Drift?
Similar fossils, climate clues, mountain ranges, ore belts, glacial evidence on opposite continents
4. What was wrong with the idea of Continental Drift (why wasn’t it accepted)?
Couldn’t show a mechanism for movement of the continents
5. Label the layers of the Earth’s interior below.
A.
B.
C.
D.
Inner core
Outer core
Mantle
crust
6. Who was the scientist who proposed the idea of seafloor spreading? Harry Hess
7. Explain how the age of the seafloor and paleomagnetism show that seafloor spreading
occurs. The age of the seafloor and paleomagnetism show a mirror-image of themselves on either side
of mid-ocean ridges, suggesting that the ocean floor is created there and destroyed in the trenches.
8. Which theory states that the Earth’s lithosphere is broken into large slabs or sections,
called plates, which move and interact with one another? Plate tectonics
9. Label each of the three major types of plate boundaries below.
A. Divergent
B. Transform fault
C. Convergent
10. What is the driving force for plate motion within the lithosphere? mantle convection
Match the plate boundary type with the geologic structure it forms below.
11. Continent-continent divergent = rift valley
12. Continent-continent convergent = mountain range
13. Continent-ocean convergent=volcanic arc
14. Ocean-ocean convergent=island arc
15. Ocean-ocean divergent=rift valley (mid-ocean ridge)
16. Continent-continent transform=fault
17. Ocean-ocean transform=fault
Geologic Structures
Fault
Volcanic arc
Island arc
Mountain range
Rift valley
18. What is subduction?when one plate descends beneath another at a convergent boundary
19. What ocean floor feature forms as a result of subduction? Ocean trench
20. Explain the difference between the focus and epicenter of an earthquake. The focus is
the origin/underground of an earthquake, the epicenter is point above the focus
21. Which nation suffered major damage and casualties from a 9.1 magnitude earthquake
in 2011? Japan
22. What is a tsunami? A seismically-generated seawave which floods coastlines
Using the P and S-wave Travel Time Graph above, answer the following questions.
23. How far can a P-wave travel in 7 minutes? 4000 km
24. How far can a S-wave travel in 10 minutes? 3000 km
25. A p-wave from a recent earthquake arrived at a seismograph station at 7:08 am. The swave from the same earthquake arrived at 7:14 am. How far away is the epicenter from
this station? ~ 4000 km
26. If a seismic station is located 2000 km from the epicenter of a strong earthquake, how
long after the p-wave arrives will it take for the s-wave to arrive? 3.3 minutes
27. How many seismograph stations is required to find the location of an epicenter? 3
28. Describe the process of locating the epicenter of an earthquake using circles and
triangulation. Using the travel time curve, find the distance from epicenter of at least 3 locations. Draw
circles using that distance as the radius from each city. Where the 3 cross is the epicenter.
29. What is the relationship between plate boundaries and earthquakes and volcanoes?
Earthquakes and volcanoes occur mostly at plate boundaries.
Match the volcano type to its attributes on the right.
30. Largest volcanoes = shield
31. Smallest volcanoes = cinder
a. Composite
32. Most destructive = composite
b. Shield
33. Hawaiian-type = shield
c. Cinder cone
34. Olympus Mons, Mars = shield
35. Mt. St. Helens = composite
36. Sunset Crater, AZ = cinder
37. Made of layers of lava = shield
38. Made of layers of tephra = cinder
39. Made of layers of both lava & tephra = composite
40. Erupts mainly cinders, ash, & gases = cinder
41. Which three cities were used in triangulating the epicenter of this earthquake?
Washington, DC, Oklahoma City, and Vancouver
42. Which city is where the epicenter of this earthquake is located?
Denver
43. Which seismograph station received the first p-wave (of the three involved)?
Oklahoma City
44. Which seismograph station (of the three) had the largest gap between p-wave and swave arrival time? Washington, DC