Historical Geology

• Age of Earth: ~4.54 billion years (± 0.05 billion years)

• To understand Earth’s past, we use forensic analysis and observations to determine who, what, how, and why.

• Uniformitarianism: the geological principle that the processes occurring in the present have operated in the same manner and at similar rates in the past.

• We can determine a lot about the Earth using fossil records and geologic time.

Past Provides Clues for Our Future

• Dinosaurs appeared at the end of Cretaceous

• ~90% species disappeared at the Triassic/Permian boundary

• Animals suddenly appeared

Maps

• Topographic Maps: detailed, accurate graphic representations of features that appear on the Earth's surface, showing both natural and man-made elements, including elevation contours to represent the shape and height of the terrain .

  • Close lines indicate steep slopes while further apart lines are lines of equal elevation.

• Geologic Maps: detailed representations of the distribution, nature, and age of rock formations and other geologic features on the Earth's surface.

• Cross-sections: vertical profiles that show a side view of the arrangement and relationships of rock layers and geological features beneath the Earth's surface.

  • May show features such as layers of rock formations, intrusions, water flow, etc.

Scientific Method

What is Science?

• Science uses observations, experiments, and calculations to explain how something works

• Critical thinking needed to get verifiable results

Scientific Method

• Recognize a problem and/or make an observation

• Collect data

• Form a hypothesis

• Test hypothesis through experiments (field work, labs, etc.)

• Validate or refute hypothesis

• Revise hypothesis and retest again if needed

Scientific Theory

• Theory: a hypothesis that has not yet been proven wrong; abundance of evidence. Explains how and/or why things happen; can be used to make predictions. Arises from tested hypotheses.

Scientific Law

• Law: A concise statement of what will happen, but does not explain how or why they work.

Three Great Themes in Earth History

Deep Time

• Deep time: immense amounts of time

Plate Tectonics

• Plate tectonics: the large-scale deformation of rocks in Earth's outer layers, serving as a comprehensive theory that explains many geological phenomena.

Evolution of Life

• Evolution: unifying theory for understanding history of life

• Fossil records help us understand changes through time