OC 201, Oceanography Winter 2021
Lab 2: Marine Geological Evidence for Plate Tectonics
In this lab, you will be using GeoMapApp to examine some of the evidence used by marine
geologists to develop the theory of plate
...
OC 201, Oceanography Winter 2021
Lab 2: Marine Geological Evidence for Plate Tectonics
In this lab, you will be using GeoMapApp to examine some of the evidence used by marine
geologists to develop the theory of plate tectonics. Remember what that evidence was:
A. Bathymetry of the ocean floor that revealed ridges (some with central rifts), trenches, and
seamounts.
B. Location and depth of earthquakes relative to seafloor bathymetry.
C. Age of the ocean floor and how it changed away from the ridges (= rises).
D. Magnetic striping of the seafloor with crustal rocks having different polarity.
In today’s lab we will explore aspects of B and C.
Part 1. Determining Spreading Rates
Your GTA will show you how to start GeoMapApp. Under the DataLayers tab select
Geophysics, and then Lithospheric Plates, and finally Seafloor Crustal Age (Muller 2008 v3).
The Seafloor Crustal Age grid will load and “Contributed Grids” and “Layer Manager”
windows will appear. In the GeoMapApp window, turn on the Zoom Tool (+) and zoom in to the
South Atlantic seafloor between Brazil and Africa by clicking and dragging.
Part 1.A: In the main window with the seafloor map, turn on the “Distance/Profile Tool” (to the
left of the “XYZ” button) in the map window and draw a profile from west to east across the
South Atlantic seafloor at a latitude of 20-30 S. Make sure your profile line is perpendicular to
the spreading ridge it crosses. When the cursor is released, the profile appears in a new window.
You may need to move the Profile window if it covers your map. It should look like a V and be
similar to the profile on the next page. Note that you might need to resize the profile box to
get the y-axis labels to appear.
Spend some time exploring and studying the profile and answer the following questions in the
boxes provided. To type in the boxes, position your cursor in the box and click twice. Do not
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