Download Oceanography—Plate Tectonics Name

Oceanography—Plate Tectonics
Name:________________________
A combination of ideas lead to the development of the theory of plate tectonics. The first
important idea—continental drift—was proposed by Alfred Wegener in the early 20th century.
Wegener observed that in a number of areas of the contemporary world, coastlines seemed to
match as though they had once been part of the same continent. He hypothesized that continents
“drift” or slowly move over time to new positions.
Little evidence (other than the matching coastlines) existed at the time to support his idea,
and it remained dormant until years later, when fossil evidence and seafloor maps became more
detailed. Interestingly, fossils from now-distant continents matched, and provided evidence that
they had once been linked. The next major idea proposed was that of seafloor spreading. This
concept—based on observations of the ocean floor and the relative distance of continents—
suggested that the ocean floor was expanding, and that the openings generated by this expansion
were volcanically active. Seafloor spreading tells us that new seafloor is created at mid-ocean
ridges and is eventually consumed at oceanic trenches.
Together, these ideas made up the theory of plate tectonics: the Earth is composed of 1015 large plates that essentially “float” on the plastic upper mantle, moving in relation to one
another. Plate tectonics is a powerful theory that explains why earthquakes generally only occur
in certain locations, decodes the “Ring of Fire” phenomenon, and reconciles continental drift
with seafloor spreading.
1. On the cross-section of the Earth below label the crust, mantle, and core.
2. Draw a picture of the “floating plates” from at least one boundary type.
3. Complete this sentence. Continental crust floats higher than oceanic crust because
________________________________________
4. Draw a diagram of seafloor spreading. Add arrows showing how the mantle is convecting,
and how that convection affects the surface of the Earth.
5. What is the driving force of seafloor spreading?
Go to the Oceanography website. Open the Plate Tectonics websites file. You will use that
file to link to various websites for this activity, so leave that page up.
Different Types of Plate Interactions
Click on the Plate Interactions link: http://www.pbs.org/wgbh/aso/tryit/tectonics/. Click on the
link to “Plate Tectonics Activity” (near the green arrow). When the window pops up, try moving
the various plates around. Notice particularly where on Earth each type of interaction can be
found. (Look at the little map!) This simulation models the four types of plate interactions that
occur on Earth.
6. What are the four different types of boundaries between tectonic plates?
Go back to the first page and follow (and read) each of the links below where it says “To find out
more, check out these…” Use the information there to answer the following questions:
7. Briefly describe (use arrows if you want) how each of the four boundary types work and
what effect they have on the Earth’s surface.
8. What type of boundary is particularly susceptible to earthquakes?
9. What type has lots of volcanic activity?
10. What is subduction? Why do oceanic plates always “lose out” to continental plates?
Age of the Ocean Floor
Go back to the Plate Tectonics websites. Click on the links under Age of the Ocean Floor.
Look at the Map of the Atlantic website.
11. Where are the youngest rocks on the Atlantic Ocean floor found?
12. Where are the oldest rocks in the Atlantic found?
13. What does this tell you?
14. What type of plate boundary is found in the Atlantic Ocean?
Click on NOAA’s Age of the Ocean Floor Poster website. Scroll down to see the large,
brightly colored Pacific Ocean floor. The continents are grey.
15. Where are the youngest rocks on the Pacific Ocean floor found?
16. Where are the oldest rocks in the Pacific found?
17. Draw a picture of the plate boundaries in the Pacific Ocean. (They are the dark lines with
tiny dots amongst the bright colors.) Label the plate boundaries as divergent, convergent,
collision, and transform where appropriate.
Earthquakes
Go back to the Plate Tectonics websites. Click on the links under Earthquakes. Make sure to
check out all 6 maps.
18. Record at least three observations from these 5 websites (collectively).
Go to the Plate Tectonics websites again. Click on the World-Wide Earthquake Locator link.
Explore the map by checking various boxes. Click Refresh Map to update.
19. Name at least 2 additional features this map has that the previous maps did not.
Volcanoes
On the World-Wide Earthquake Locator
20. What similarities do you see in relation to earthquakes and volcanoes?
From the website, click on the Map of World Volcanoes link. Scroll down to see the map.
21. Click on a region that interests you (below the world map). Record the name of a volcano in
that region.
Tectonic Plate Boundaries
Now take a look at the map of the world’s plate boundaries at the last website listed.
22. What do these 3 types of maps (earthquakes, volcanoes, and plate boundaries) have in
common?
23. List evidence that supports the theory of plate tectonics.