This lab module was undertaken to investigate the general question:

How do geologists see, think and talk about the earth?

To gain understanding of the geologists' world, you tackled a specific geologic problem:

How did the landforms of the New York City region originate?

In doing so, you became acquainted with geologists' hypotheses, were introduced to geologic processes and materials, learned how geologists collect and play with data. Importantly, you gained insight into how geologists make predictions and evaluate them to test their hypotheses. Furthermore, for two of the four major landforms of the NYC region, you accepted as "uncontroversial" an origin involving differential erosion. You made this decision because (a) predictions you made to test the hypothesis were fulfilled and (b) the competing hypotheses seemed 'unlikely'.

Two important question remain to be answered:

  • What do geologists consider to be the origin of the remaining two landforms?
  • What is the nature of the argument that has convinced them?

In geology, as in other sciences, a hypothesis that becomes generally accepted is called a 'theory'. One way in which a hypothesis may become a theory is if it satisfactorily explains the origin of many diverse phenomena or provides answers to many diverse problems. A hypothesis that has this ability gains a significant advantage over competing hypotheses.

A famous theory in geology is the 'Glacial Theory'. In accepting this theory, geologists became persuaded as to which hypothesis of origin for the two remaining major landforms had a distinct edge and could be considered "uncontroversial". Thus, to complete your consideration of the origin of the landforms of the NYC region, you need to understand the Glacial Theory.

You need to do the following:

  1. Click on this blue button to review Glaciers. 

  2. Click on this blue button to learn about the Glacial Theory.  

  3. Click on the button and print the Glacial Theory Worksheet (Q-12).
  4. In the appropriate places on the worksheet:
    1. Explain briefly the 'Glacial Theory'. (Do not include an explanation of how glaciers erode, transport or deposit rock debris, or how the Glacial Theory applies to the NYC region.)
    2. In addition to the examples provided, list one major landform, one material, and one small-scale landform in the NYC region that are capable of being explained by the Glacial Theory.
      (Note: Your major landform, material, and small-scale (minor) landform do not have to be from the same geographic location.)
      (Note: Not all features in the NYC region are explainable in terms of the Glacial Theory. Do not list features for which an "uncontroversial" non-glacial origin has been proposed.)
    3. For each feature you have listed, very briefly explain its origin in terms of the Glacial Theory.
    4. In the text box below, state and justify your opinion as whether the Glacial Theory should more properly be called the 'Glacial Hypothesis'. Do so using the criterion of being able to successfully explain diverse phenomena. Include a brief statement explaining the difference between a hypothesis and a theory.


  1. For each of the following 5 questions:
    • Propose answers in the form of two hypotheses.
    • For each hypothesis, make a prediction that will be a good test of the hypothesis.
    • For each prediction, draw upon your knowledge of the geology of the NYC region and your general knowledge of geologic processes and materials to evaluate the prediction.

    1. How did the parallel hills and valleys of Manhattan, the Bronx, and adjacent New Jersey originate?

    2. How did the belt of randomly shaped hills and valleys of northern Brooklyn and Queens originate?

    3. How did the gently sloping, flat plain of southern Brooklyn and Queens originate?

    4. How did the isolated boulders get to their present locations?

    5. What is the origin of the numerous parallel scratches and grooves on the bedrock?

  2. Answer the following two questions:
    1. Do geologists demand that their answers to problems be conclusively 'proven'? If not, what value do geologists' conclusions have? Explain your answer.

    2. Does the "Glacial Theory" merit the term 'theory'? Support your answer by citing specific examples.

David J. Leveson