Lab 9 - Exploration of the Toadstool
Lab goals: The
purpose of this lab is to: 1) teach you how to navigate in and
complete some simple tasks with ArcGIS 9 software, and 2) learn
about the structural geology of Toadstool Geologic Park in northwest
Nebraska. This and other localities in the central Great Plains
offer us the opportunity to investigate episodes of intraplate
strain. Joints, veins, arrays of small faults, and subtle flexures
combine with intraplate earthquakes to indicate that while the
interior of plates are relatively 'rigid' they do deform a bit.
This subtle deformation can be quite important for fluid migration,
erosional patterns, and erosion/deposition dynamics. Later on
in the semester you will build your own small GIS database for
some locality of Great Plains strain.
What you should turn in: Having navigated and manipulated the database information
in ArcGIS 9 a little I would like you to explore what might be
learned from this type of data in a GIS environment. Come up
with three simple statements that describe some aspect of the
pattern of faulting, and then print of an image to support each
statement. The image should have a scale. Come up with
two statements that summarize something about vein attributes.
Again you should support your statements with exemplary images.
Choose the wording of your statement carefully. So your final
hardcopy product will be 5 one-sentence statements, connected
to 5 map images.
Navigating in the ArcGIS environment: The below is intended to be step-by-step instructions
to help you complete this lab. You might check them off as you
- Copy the folders Toadstool and Harlan
on the CD to the C drive. ArcGIS assembles
files and part of the master (.mxd) file are the addresses of
the other files. If those addresses are wrong, ArcMap can't find
the files. For the .mxd file you will work with, the Toadstool
folder needs to be on the C drive. You can reconstruct pathways
to the original files, but we can save that for another lab and
- If you can save changes you make while working
in the program, right click on the folder icon, and deselect
the read-only option. This way you can save changes to your C-drive
- Navigate into the ToadstoolGIS folder
and into gisfiles folder within and double click on toadtotal.mxd.
The mxd suffix tells you that this is a ArcMap master file, that
opens up an already constructed GIS database. Two windows should
pop up. To the right is a map and to the left is a list of layers.
- At the top choose the View tab, and
the select the Data View option. This program was saved
so that the Layout View comes up. The Layout View
is where you put the finishing touches on a map, and consider
its graphical presentation. The Data View is where you
add, delete, analyze and manipulate the various layers of information.
When you want to produce a finished product you can change back
to Layout View.
- Note the Tools bar with the small
magnifying glass icons at top, one with a plus sign to zoom in
and the other with a minus sign to zoom out. Note also the scroll
bars on the bottom and right of the map window. Select the zoom
in or zoom out tools, and use these to scan through the map area
and become familiar with the landscape and plotted geology.
- Note the small boxes in the Layers
window just to the left of listed layer names. Some of these
are checked and some are not. Experiment to see what happens
when you check of uncheck them.
- Right click on the faults layer and
select the Open Attribute Table option. Scroll through
the table that opens up. Here is the data behind the map view.
Note that not all the data is being used or displayed in the
map window. You will learn one way to explore the other columns
of data in the table in a map view. In this lab, if you want
you can simply move the table over to the other screen for later
reference. Otherwise you will want to close this window.
- Right click on the fault layer and a box
will open up and check the Label Features option. What
happens on your map view? Right clicking often is a way to look
for possibilities when you want to do or change something. What
type of information are the faults being labeled with (you might
check the Attribute Table)? Things can get pretty cluttered,
so you might want to turn the Label Features option off.
- We are now going to create a new layer and
classify information in it. Specifically, we are going to see
what the spatial variation in average vein thickness is.
- Navigate and zoom in on one of the vein fields.
- Right click on the veins layer and
choose the Copy option.
- Go up to the very top of the Layers
window and right click on Layers, and choose the Paste Layer(s)
option. The new layer should now be listed in the layers window.
- You should be able to type in a new name
for this copied layer. Vein thickness might be a good descriptive
name. You can change the name of any layer by double left clicking
on the name itself, and then typing in the new name.
- Now right click on this new layer and choose
the Properties option at the bottom of the list. A fairly
complex window full of options should pop up. This is a very
important place in this software. Here you can change what information
is displayed, and how it is displayed. It is also where you can
classify your data, a first step to analyzing spatial patterns.
- If not already selected, choose the Symbology
tab at the top of your Properties window.
- In the subwindow to the left choose the Quantities
option. Highlight the Graduate symbols option. This allows
you to classify a column of data and plot a symbol at the specified
location whose size or color is a function of the data value.
Here we can plot the average vein thickness measured at each
- We still have to tell the program what column
of data in the Attribute Table to classify and plot. In the larger
internal box in the window find the Fields Values scroll box
and choose AVERAG_TH choice. A suite of graduated symbols
should appear in the Symbology window. There are all sorts of
options you can explore here, but to start out with it may be
best to use the default symbols.
- Select OK and see what is now plotted on
- One way to get output is to export the map
window as an image. Under File choose the Export Map
function and follow the instructions to save the image as one
of several formats. An important part is to choose the right
format with the Save as type scroll box below. Jpeg is
the easiest to work with. This can be pasted into a Word file.
- If you want you can also open the localities.mxd
file and explore it.
- More description of how bring your lab data
into the ArcGIS
environment and on the Toadstool
project exists here. This would be good preparation material
for our field trip. Cheers!
Copyright Harmon D. Maher Jr., This may be
used for non-profit educational purposes as long as proper attribution
is given. Otherwise, please contact me. Thank you.