GEOLOGY 5543 - PLATE TECTONICS
EXERCISE 05- FALL SEMESTER, 1999
PHYSIOGRAPHY OF OCEAN BASINS I - Due Monday, 10 Oct 1999
INTRODUCTION
This week's assignment is the first where we will query the ETOPO5 database file in order to generate 3-D images of various tectonic settings around the world. To do this, we will be exploring "gridding" functions available in Vertical Mapper, which is a plug-in to MapInfo. To begin our gridding and 3-D imaging exercise, we will derive images from several important physiographic/tectonic settings found in the ocean basins. As you work through this exercise, try to gain an appreciation for the distinctive features of these different environments and imagine the geological processes that are responsible for their evolution in time.
ASSIGNMENT Part A - Get the Data
To obtain the necessary data for this week's assignment, you have the choice of either querying the ETOPO5global file that we have already created, or returning to the Gridded 5-minute Global Relief Data site at the National Geophysical Data Center. There are advantages and disadvantages to either method, but in the end it doesn't matter which strategy you use. The coordinates of the data we wish to examine are given in the following table:
NAME UPPER LEFT LOWER RIGHT HATTERAS ABYSSAL PLAIN 37.29oN 74.81oW 31.80oN 69.61oW ABYSSAL HILLS 30.53oN 54.36oW 21.80oN 50.30oW MID-ATLANTIC RIDGE 23.77oN 50.37oW 18.63oN 42.75oW EAST PACIFIC RISE 18.75oS 118.75oW 25.75oS 109.75oW If you choose to go back to the web to download data from NGDC, you will need to follow tha same procedures we followed for Exercise #01 for editing your data file and importing it to MapInfo. Once that is done, you will be able to proceed to Part C below. If you choose to query the ETOPO5global file that we've created in class, then follow the instructions in Part B below.
ASSIGNMENT Part B - Query ETOPO5global Using MapInfo
Load ETOPO5global.TAB when you start MapInfo. For each of the physiographic/tectonic settings in the table above, you will need to query the database two times in order to isolate the data of interest.
Once ETOPO5global is loaded, go to the Query function on the main menu and click on "Select". When you see the "Query" dialogue box, select the appropriate items to complete the operation. Make sure "ETOPO5global" is entered in the "Select Records from Table" box. In the "That Satisfy:" box, enter the phrase
_COL1 between -XX.XX and -YY.YY
where XX.XX = the lowermost (i.e. westernmost) longitude and YY.YY = the uppermost (i.e. easternmost) longitude. Note that because all the sites we are examining this week are located in the western hemisphere, the longitude values must be entered as negative numbers. Once you have entered the appropriate phrase, check you entry to be certain the westernmost longitude is first and the easternmost longitude is second. Then hit "OK" and wait until the request in completely processed - be patient, it may take awhile.
When the query is completed, you should see a new table labeled "Query1" on screen. Keeping "Query1" as the active window on screen, go back to the "Query" function of the main menu and choose "Select" again. When you see the dialogue box, check again to make certain the correct items appear in the windows. In the "Select Records From Table:" window, make sure "Query1" is selected, not ETOPO5global. Then, change "That Satisfy:" to read
_COL2 between -AA.AA and -BB.BB
where AA.AA = the lowermost (i.e. southernmost) latitude and BB.BB = the uppermost (i.e. northernmost) latitude. Once you have entered the appropriate phrase, check you entry to be certain the southernmost latitude is first and the northernmost latitude is second. Then hit "OK" and wait until the request in completely processed - again, be patient, it may take awhile. When you see the new table labeled "Query2" on your screen, go to the "File" function of the main menu and choose "Save Copy As..." When you see the dialogue box, make sure you highlight "Query2" among the choices, the click on "Save As...". At the next dialogue box, make sure the file is targeted to be saved in the Plate Tectonics folder, then give it a clever new file name such as AbyssalPlain_yourname.TAB and click on "Save". When the file is done saving, go to the "File" function again and choose "Close Table...". Select "Query1" and Query2" and click "OK".
Repeat the procedure above for each of the 4 tectonic settings for this exercise, then proceed to Part C below.
ASSIGNMENT Part C - Map the Data
Once you have saved tables for each of the 4 tectonic settings, open one of them again and go to the "Vertical Mapper" function of the main menu. Choose "Create Grid...", then "Interpolation". When the dialogue box appears, select "Natural Neighbor." by clicking once on the icon, then click "Next".
Choose the file name "AbyssalPlain_yourname", _COL3, _COL1 for the X column, and _COL2 for the Y column. Choose "Longitude/Latitude" for the "Projection" and "Meters" for "Unit Type". Then click "Next" again.
When you see the dialogue box named "Simple Natural Neighbor Interpolation", enter a new file name (say, AbyssalPlainMap_yourname) in the window at the bottom of the dialogue box. Make sure the path for the file is to the Plate Tectonics folder. Then click "Finish". Be patient - this part can take a while to complete.
When processing is complete, you will see a colored relief image of your area. Once this appears, click on the "Grid Manager" icon of the VM2 or VM2.5 tool bar (we used this tool to generate the contour map in exercise #03). When the "Grid Manager" window appears, click on the "Color" icon. You will see a graph showing the range of depths on your map and the colors that are assigned to those depths. For all of our images, we will want to use a 500 m interval. To change the depth values, double click on the numbers corresponding to depth in the column labeled "Value". To add additional depth points, double click on the line with markers under the histogram of depth distribution. Adjust the depth value by double clicking on the "Value" column and entering an new number. When finished, click on "OK".
Now, click on the "3d View" icon and choose "Run 3D Viewer". Experiment with the different functions that are available. Change the viewing distance, angle of elevation, lighting sources, etc. by manipulating the tabs and entering new values or by moving the slider bars.
When you are satisfied with your result, go to the "File" function of the 3D Viewer and "Print" a copy of your finished product. If you are given the option, choose to "Fit to Page" so your image will fill the entire print area of the paper.
Repeat this process until you have generated 3-D images of all 4 tectonic features of the ocean basin. When you have printed the images, please label each one and write your name somewhere on each image. We will share your views in class (hopefully, each of you will choose slightly different parameters for your final view).
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