Perspectives on Earth History
Studies in Geology
- Physical geology is the study of the materials and processes that operate on and below the Earth's surface.
- Historical geology seeks to understand the origin and development of the Earth.
- Geology has been the subject of written speculation for 2000 years.
- Aristotle's peculiar pronouncements clouded discussions of geology for centuries.
- Relies upon sudden, devastating and dramatic changes (floods, volcanic eruptions, etc) to account for geologic formations.
- Those catastrophes no longer seemed to be occurring.
- Popular during the 17th and 18th centuries.
- Uniformitarianism states the physical, chemical and biological processes at work today are the same processes that have been at work throughout the Earth's history.
- Proposed by James Hutton. In his 1788 paper, he stated "...we find no vestige of a beginning - no prospect of an end."
- In 1830, Sir Charles Lyell published the first edition of Principles of Geology, a tremendous advance for modern geology.
- Lyell's extensive geologic observations in North America and Europe supported uniformitarianism.
- Today, actualism uses both gradual and catastrophic events for a more comprehensive, expanded view of geologic processes.
- In 1980, Mt. St. Helens had a dramatic, cataclysmic eruption.
- Now gradual processes of weathering and erosion are acting on the volcanic peak.
- We do not assume that the rates or intensities of geologic processes remain constant over geologic time.