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10: Geologic History

Last updated

Apr 1, 2025
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- 9.2: Mountain Formation
- 10.1: Relative Ages of Rocks

Lumen Learning
Lumen Learning

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10.1: Relative Ages of Rocks
This page details the evolution of geological thought from Nicholas Steno's 1666 work on fossils and rock formation principles, which challenged existing beliefs, to James Hutton's introduction of uniformitarianism and the importance of geological time.
10.2: Absolute Ages of Rocks
This page discusses methods for determining relative and absolute ages in geology, focusing on techniques like tree ring counting, ice core analysis, and varve study for recent events, alongside radioactive decay for older rocks. Absolute dating provides specific ages through radiometric techniques, such as carbon-14, potassium-argon, and uranium-lead dating.
10.3: Fossils
This page discusses the historical fascination with fossils, which inspired myths like dragons. Fossilization, a rare process influenced by decay and environment, includes methods like permineralization and molds. Key fossil sites offer insights into ancient organisms and evolutionary changes. Fossils help trace Earth's history, indicate past climates and environments, and document significant events, such as mass extinctions.
10.4: History of Earth’s Life Forms
This page covers the discovery of Cambrian fossils by Charles Doolittle Walcott, highlighting the evolution and adaptations of species over time. It discusses the fossil record's importance in understanding life's development and the role of mass extinctions.
10.5: Early Earth
This page envisions a film chronicling Earth's 4.5 billion-year history, detailing its transition from an inhospitable state to a thriving biosphere. It highlights significant geological transformations, the emergence of life through simple organisms like cyanobacteria that enriched the atmosphere with oxygen, and the resultant formation of the ozone layer.
10.6: Geologic Time Scale
This page discusses Earth's 4.5 billion-year history through the geologic time scale, which categorizes significant events and organisms into eons, eras, and periods based on fossil evidence. Historical geologists initially used relative dating for rock layer organization but later applied absolute dating techniques, like radioactivity, for precise dating.

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