Early Geologists Tackle Earth’s Mysteries CHAPTER TWO Early Geologists Tackle Earth’s Mysteries

Historical Geology Sparked by The Discovery of Fossils Remains or traces of prehistoric life. They can tell us much about the history of the Earth and life. A record of plants and animals which lived and died over an immense span of time.

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KEY PEOPLE Niels Stenson “Nicholaus Steno” Abraham Werner James Hutton John Playfair William “Strata” Smith Leopold Cuvier Sir Charles Lyell Charles Darwin

Niels Stenson “Nicholaus Steno” (1638-1687) Formulated 3 Principles Superposition Original Horizontality Original Lateral Continuity These 3 principles are the basis of Stratigraphy

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f02_04_pg14 Principal of Original Horizontality f02_04_pg14.jpg

“The tilted beds indicate something has happened.” f02_05_pg14 Principal of Original Horizontality “The tilted beds indicate something has happened.” f02_05_pg14.jpg f02_05_pg14

f02_06_pg15 Principal of Original Lateral Continuity f02_06_pg15.jpg

Neptunists Versus Plutonists Neptunists – Rocks came from water. Abraham Warner (1749 – 1817) Plutonists – Rocks came from fire. James Hutton (1726 – 1797)

Abraham Werner 3 stages of rock formation Core of mountains formed from a hot water ocean of dissolved minerals. Subsidence of ocean & deposition of fossil-bearing rock. A top layer of transition rocks – sandstones, shales, coal beds, fossiliferous limestones and old lava flows.

Abraham Werner Problems With Theory What happened to the immense volume of water that covered the Earth. How could lava flows be deposited in the same manner as limestone deposits.

James Hutton Uniformitarianism “The Present is the Key to the Past”. Earth’s History may be deciphered by observing events today and assuming that the same phenomena have operated throughout geologic time. By observing present geologic processes you can decipher historic origin of rocks.

James Hutton Problem with Uniformitarianism Earth’s processes have changed over time Different atmospheric conditions. Meteorite bombardment More active volcanoes Glaciation “Play The What If Game”

James Hutton Other scientists (John Playfair) Used the term – “Actualism” instead of Uniformitarianism. Examined past and present processes in a broader scope.

James Hutton Viewed the world as a series of cycles Constructive and destructive processes. There is no beginning or end. Rocks recorded events over immense periods of time. Earth experienced many episodes of mountain-building episodes.

James Hutton Unconformities Gap in the rock record caused by periods of deformation and erosion. In a normal sequence, rocks are deposited in a defined sequence. An unconformity causes this sequence to be broken.

James Hutton Unconformities Three types Disconformity Nonconformity Angular Unconformity

The Principle Fossil Succession (William “Strata” Smith – 1769-1839) Incorporated the principles of stratigraphy in Canal Excavation Projects. Traced Strata from place to place using similar fossils.

Catastrophism (Baron Georges Leopold Cuvier – 1769-1832) Concluded that the history of life was marked by frightening catastrophes involving flooding of continents and coastal upheavals. Looked at “Noah’s Flood” as most recent. Thought that each catastrophe completely extinguished life forms and was followed by the appearance of new animals and plants.

Principle of Cross-Cutting Relationships (Sir Charles Lyell – 1797-1875) Features that are cut are older than features that do the cutting. Intrusions Faults Unconformities Erosion

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Evolution “How Organisms Change Through Time” (Charles Darwin – 1809-1882) 5 Year Stint on H.M.S. Beagle Evolution of organisms is due to natural selection Organisms of the same type differ from one another in morphology and physiology Individuals with the most favorable for survival and reproduction in a given environment would have best chance of surviving and passing on these traits to next generation – “Natural Selection”

Theory Summary Niels Stenson “Nicholaus Steno” Abraham Werner Superposition, Original Horizontality & Lateral Continuity Abraham Werner Neptunist, 3 Stages of Rock Formation James Hutton Plutonist, Uniformitarianism, Unconformities, Constructive/Destructive Processes John Playfair Actualism

Theory Summary - Continued William “Strata” Smith Fossil Succession, Stratigraphy Leopold Cuvier Catastrophism Sir Charles Lyell Cross-cutting relationships Charles Darwin Evolution

Earth History In America “1800’s” Glaciers Lousi Agassiz Stratigraphy of New York James Hall Western Geology Ferdinand Hayden: Badlands of South Dakota John Powell: Grand Canyon Dinosaur Rush Othniel Marsh Edwin Cope

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