Geological Principles Used During My Hurricane Katrina Field Research
Geological Principles that Apply to the Hurricane Katrina Study
When geologists study rock strata, they used direct observation with geological principles to determine relative age of the rocks or an event within the rock record. When I investigated Hurricane Katrina debris, I relied on these Geological Principles of Relative Dating to explain the order the events that happened during this destructive hurricane.
One, Geological Principles of Relative Dating is called Original Horizontal. In sedimentary investigations geologist can determine events that took place. An example is when rock layers are formed flat or original horizontal, and at a later time the rock layer is uplifted. The debris field left over from this hurricane was sedimentary. Although, I had to deal with debris from cars, trucks, houses, trees, rocks and sand.
A second, Geological Principle of Relative Dating is called superposition. Superposition helps to determine relative age by stating that the different layers were deposited at different times. The older layer is lower than the younger layer on top of it. In the above picture A is younger than B. Geologists can often determine yearly events due to seasonal changes as well as current and wind direction within sedimentary rock. I use this technique to order the events that took place during Hurricane Katrina by examining the sediment (debris field).
The third, Geological Principle of Relative Dating is called cross-cutting. Cross-cutting is an exception to the superposition principle because faulting or igneous intrusion can cut into existing rock. The cross-cut event is younger than the rock it cuts. See drawing below. I used this technique to determine the order of the events and the direction the tractor-trailer boxes moved over the lot.
The last Geological Principle of Relative Dating that I used was inclusion. Inclusion recognizes that under curtain conditions rock strata that has igneous rock under it may be older or younger, but if pieces of rock are mixed with the above sedimentary rock, it was weathered from the rock below and now part of the new rock above. I used this technique to determine that the tractor-trailer box ran over the house during Hurricane Katrina. Since part of the house become part of the wheel, the house was weathered when the tractor-trailer box run into it. Both the house and the tractor-trailer box became one piece of sediment that was deposited together.
Suggested Reading and Web Sites:
Conceptual Physical Science-Explorations, Hewitt, Suchocki and Hewitt Published by Addison Wesley 2003
Evidence of Glaciation
http://www.geol.umd.edu Paleomap Project