What is the nature of history? What mix of revolutions and evolutions, of sudden change vs. slow change? How sensitive is the course of history to small events and changes? What variations in behavior are possible? For these and many other very basic questions geology provides insight. New focus is on the history of climate change, as we seek to know changes to come.

Rates and perspective -> fault motion as an example. Continuous vs. discontinuous phenomena.

The character of history and a host of -isms:

• uniformitarianism: key to the past is the present.
• actualism: same basic physical laws operated in the past.
• gradualism: slow, incremental changes are key to understanding geologic history.
• catastrophism: anything goes, the bigger the better.
• creationism: a creator did it, end of ability to investigate through science. Religion, not science.
• neocatastrophism: big catastrophic events are actualistic, the inevitability of the improbable given enough time.
• punctuated equilbrium (ism): gradualism + neocatastrophism.

How big? The case history of the wave that paved Lanai:

• Hawaiian island with unique deposit of basalt and coral fragments up to 375 m elevation on slopes.
• old explanation?
• need for new explanation.
• mutliple working hypotheses of causes.

Accidents happen: the Mesozoic-Cenozoic boundary clay:

• major extinction boundary.
• iridium anomaly, shocked quartz, microdiamonds, much more in this distinctive layer.
• 3 schools of thought: volcanic, impact, and denial.
• evidence now fairly conclusive that impact in north Yucatan area played a critical role.

Milankovich cycles: the regular and predictable vs. chaos? Sedimentary cyclothems in the record.

Major events in earth history:

• development of an oxygen rich atmosphere.
• Snowball earth hypothesis. A new twist.
• Cambrian faunal explosion.
• Paleozoic-Mesozoic extinction boundary.
• Earth in high volcanic gear in the Cretaceous.
• Mesozoic-Cenozoic extinction boundary.
• Development of the technologic species?

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