Introduction

Charts and maps are basic tools of ocean navigation. They contain important information such as ocean depth, geographic features and landmarks, and latitude and longitude. So there’s a volcano below you, can the day get any worse? In the map case you find a bathymetric map of the Pacific Ocean (how convenient). Notice how many other atolls are on the map. This used to be a volcanically active area!

The Captain’s Orders

To help you understand the oceanic world, you’ll need to refresh your mapping and navigational skills.  There is a computer on the Captain’s desk. You’ll need to use it to help you complete the task for the Captain. Answer the following questions using your survival skills and the internet. 

Objective

Interpret ocean floor physiography, relief, and depths from bathymetric maps and charts.

Questions

Answer the following questions using your survival skills and the internet.

1. Explain what a bathymetric map is. In your explanation, describe how it differs from a topographic map.
2. What’s the average depth of the oceans?
3. Where is the deepest spot in the ocean? How deep is it?
4. What is the name of the deepest spot in the ocean?
5. There are a lot of features in the bottom of the sea. Navigate to http://www.purposegames.com/game/ocean-basin-quiz and start the Ocean Basin activity. Take a screenshot of your results.

Bathymetric Maps

Bathymetry is the measurements of water depths. One way to visualize the seafloor is by using a contour map. Contours are lines drawn connecting points of equal depth. It’s like “connect the dots” but with a twist. The lines are called isobaths, a line on a map that connects all points having the same depth below sea-level. Watch the first 6 minutes of this video, How to Draw Contours http://www.youtube.com/watch?v=L6FbV0LiA_k. The twist is that the depths for the isobaths may not be marked on the map; you’ll have to make an educated guess.

1. Looks like the boat captain didn’t finish drawing this bathymetric map. He managed to draw the 500-foot isobar. Draw the 485, 490, 495, 505, and 510 feet isobars.
   
   Figure 1. Bathymetric map with the 500-ft contour line.
2. This map contains a bunch of soundings. Complete this contour map using a contour interval of 10 feet starting at 80ft, 90ft, … to 130 ft. For now, ignore the line connecting points A and B.
   
   Figure 2. Soundings map with points A and B.
3. Once you have drawn all the isobars, take the edge of a sheet of paper, and line it up with the gray dotted line. Mark the letters A and B on your paper. For every spot an isobar touches your paper, make a tick mark and write down the depth. 
   
   Figure 3. A pirate constructing a contour profile map of the ocean floor.
4. Take the sheet of paper, line it up with the graph paper and plot the depths on the graph below.

    
   Figure 4. A blank contour profile map.

How to Submit Your Task

Answer the four questions on a word processing document. Once you have finished the assigned task, submit the document to the Captain’s dropbox, including a screen shot of your Ocean Basin activity, and Figure 1, Figure 2, and Figure 4.