Geology 12 - Historical Geology
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Stratigraphic Principles

Reading: Chapter 1, 2 & 4

If you do not have the textbook, use these Web sites to answer the questions:

The six principles of stratigraphy

A history of the concept of uniformitarianism and how it contrasts with the modern concept of actualism.

Read all three pages to understand the difference between Lyell's brand of uniformitarianism and the way geologists understand the concept today.


Terms you should know:

catastrophism -


unconformity -

stratigraphy -
formation -
lithology -


Key Concepts and Questions:

1. How fast do geologic events occur?

We will do an exercise in class to help illustrate this.

Summarize here what you learned about geologic rates.




2. What does uniformitarianism - the essential paradigm of geology - mean?

a. Catastrophism - the initial assumption in studying the Earth.

What does catastrophism assume about how the Earth formed and developed?



Find a couple examples of early theories of the Earth that rely on catastrophist explanations.



b. Uniformitarianism

Read about Lyell's version of uniformitarianism. How does our modern understanding of uniformitarianism (Levin calls it actualism) differ from Lyell's uniformitarianism?




What evidence supports our uniformitarian view of the world?




3. How do we put geologic events in the proper order?

A. Principles of stratigraphy: for each, define and draw a sketch (p. 19-20, 24, 74)

Original horizontality:






Original lateral continuity:



Cross-cutting relationships:



Included fragments (inclusions):



Fossil succession:





1. Rates

You should be able to:

2. Uniformitarianism

You should be able to:

3. Stratigraphic principles

You should be able to :