Bottom of the Sea Webquest

Plate Tectonics and the Seafloor

The people who first mapped the seafloor were aboard military vessels during World War II, using echo sounders  to search for submarines. The results produced a map of seafloor depths. Depth sounding continued after the war. Scientists used this information to produce bathymetric maps of the seafloor. During WWII and in the decade or so later, echo sounders had only one beam, so they just returned a line showing the depth beneath the ship. Later echo sounders sent out multiple beams and could create a bathymetric map of the seafloor below. Using the resources provided, answer the following questions, in complete sentences, on your blog. You may copy and paste these questions and resources, to get you started.

• What is a bathymetric map? Provide a picture of a bathymetric map. What are three ways that these maps are produced?  http://www.absoluteastronomy.com/topics/Bathymetry
• What does “sonar” mean? After watching this two-minute video, describe what NOAA scientists use sonar for: http://oceanservice.noaa.gov/facts/sonar.html
• What is “seafloor spreading”?  http://www.geolsoc.org.uk/Plate-Tectonics/Chap1-Pioneers-of-Plate-Tectonics/Harry-Hess
• Describe the following image and how it occurs. Identify a location in the ocean where this may be found. http://www.geolsoc.org.uk/Plate-Tectonics/Chap1-Pioneers-of-Plate-Tectonics/Vine-and-Matthews

Magnetic Stripes

• Name the seven major and eight minor tectonic plates, and describe why they are broke into two categories.  http://www.geolsoc.org.uk/Plate-Tectonics/Chap2-What-is-a-Plate
• Explain each of the following major features of ocean basins, and how they form, providing an image for each one:
  • Mid-ocean ridge:  http://www.whoi.edu/main/topic/seamounts or  http://www.eoearth.org/view/article/164696/
  • Seamount:  http://oceanservice.noaa.gov/facts/seamounts.html and Listen
  • Continental margin, continental shelf:  http://education.nationalgeographic.com/encyclopedia/continental-shelf/
  • Abyssal plain:  http://www.education.noaa.gov/Ocean_and_Coasts/Ocean_Floor_Features.html
  • Rift zones:  http://hvo.wr.usgs.gov/gallery/kilauea/erz/erz_overview.html
  • Deep sea trenches:  http://www.livescience.com/23387-mariana-trench.html
• The Phoenix Islands Protected Area (PIPA) is the largest Marine Protected Area in the world.One dozen seamounts are within PIPA boundaries, from sea level to 5000 meters depth. Where are these islands and what is a Marine Protected Area?  http://www.whoi.edu/main/topic/marine-protected-areas

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Guest Post

Dancing of the Continents

In the “Dancing With the Continents” assignment I learned a plethora of new information about continents, plates and the way they behave. With Wagner’s original theory in 1920 saying the continents slide over the ocean floor, he had the write idea,  just not the evidence to prove it. As technology got better more evidence was found to prove this theory and in 1960 the theory of seafloor spreading was published by Hess. This explained the enlargement of the ocean floor.  In future years the theory of plate tectonics, the accepted scientific theory of ocean plate movement today, was released. It states the ocean floor is broken into large pieces (approx. 6) and many smaller pieces that move against one another.

With these theories in mind, the activity certainly gave each student a lot to think about. The entire world was shaped differently millions of years ago. We could have taken a 2-3 hour drive over to Paris back then. India was the same distance away as Florida instead of around the world. In a a couple million more years the world will look like a different place because the continents move about 2-3cm each year.  That’s amazing.

– Tom

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plate tectonics

In class we learned about plate tectonics by taking two maps and glued the contents together to make them all fit like a puzzle. We showed the connection between rocks plants and animal and put them together. The plates make up Earth’s outer shell, called the lithosphere. The lithospher is both the crust and also the uppermost part of the mantle. Churning currents in the molten rocks below move them along like a bunch of conveyor belts in disrepair. This is where the plates meet or divide.

The movement of the plates creates three types of tectonic boundaries: convergent, where plates move into one another; divergent, where plates move apart; and transform, where plates move sideways in relation to each other.

http://www.scienceclarified.com/Ph-Py/Plate-Tectonics.html
http://csep10.phys.utk.edu/astr161/lect/earth/tectonics.html

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