In this exercise, you will be provided with a 'data base' that provides information as to the actual bedrock geology of Manhattan, the Bronx, and adjacent New Jersey. This information is supplied in the form of a partially completed 'rollover' map that, as you move the cursor over it, shows the geologic material present in each area, in a fashion similar to the 'rollovers' in the two 'Practice Making A Map' exercises.

When you click on 'radio buttons' located directly beneath the 'rollover', four slightly different, fully completed bedrock geology maps of the area being investigated will appear one at a time in a 'map window'. Only one of the four maps is correct. Your task will be to determine which of the four maps is correct. To make your decision, you will compare the bedrock geology shown on each of the four maps to the actual distribution of geologic materials as shown on the 'rollover'.

To simplify the task of comparing the four geologic maps to each other so as to determine the differences between them, a compilation of the four maps on one web page is provided. As described below, you will record the differences on a 'worksheet printout'.
As you pinpoint the critical areas of difference between the four maps, you will record those differences on worksheet # GM-C. Then, you will be able to go directly to those critical areas on the 'rollover' to determine what is the actual geology and which of the maps shows the geology correctly. An 'Answer Check' is provided so you can see if your decision is correct.

An example of a filled out worksheet is provided below. It pinpoints the differences between three maps and draws a conclusion as to which is correct.


The method used to decide which map is correct involves three distinct steps:
  1. First, for each map, the proposal is made that the map is "correct".
  2. Next, 'critical areas' are located on the map. ('Critical areas' are those places in which two or more maps show a different distribution of geologic materials. Since we are told that one of the maps is 'correct', then those areas that are the same on all maps must agree with the 'rollover' and will not help in identifying the 'correct' map.)
  3. Then, a 'test' is set up, which involves a comparison between critical areas on the map and the same areas on the 'data base rollover'.
  4. Based on the results of the test, a conclusion is reached: if the critical areas on the map and on the 'rollover' agree, then the map passes the test and may be considered 'correct'; if not, the map is considered 'incorrect'.
This procedure may be described more formally as follows:
  1. Hypothesis proposal. Four hypotheses as to the correct bedrock geology are proposed in the form of four maps.
  2. Devising a test for the hypothesis. For each hypothesis (map) a test in the form of a prediction is devised. The prediction is that the distribution of geologic materials as shown on the map and the 'actual geology on the ground' will be identical. Only 'critical areas' (those locations where two or more maps differ) are examined since other areas will agree with the 'geology on the ground'.
  3. Performing the test. Critical areas of each map are compared to the 'data base rollover', which provides information as to the actual geology on the ground (the empirical data base).
  4. Hypothesis evaluation. After the comparison is made between the map and the hypothesis, each hypothesis (map) is then considered supported or not supported according to whether or not it passed the predictive tests.
  5. Comparison of hypotheses to form a conclusion. After all the hypotheses (maps) have been tested and evaluated, a conclusion is made as to which is correct on the basis of the strength of the support it has received.

Is this method 'scientific'? Explain your answer. (HINT: Look up the meaning of the phrase 'scientific method'; give your source reference in your answer.)


In this example, pretend that the 'data base rollover' (not shown in the example) indicates that the center map is correct. (NOTE: The center map isn't really correct.)
Now return to the Geologic Maps Menu and click on the NYC Bedrock Geology Investigation.

© 2010
David J. Leveson/Revised by G. Rocha and Michelle O'Dea