EARLY THEORIES Foundation of GY 112

Historical Geology Sparked by The Discovery of Fossils 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.

How do fossils form? Rapid burial with sediment, preserving the hard parts. Freezing, as in glacial ice. (Example: Pleistocene wooly mammoths frozen in Siberia and Alaska.) Desiccation (drying or mummification). Preservation in tree sap or pine resin that hardens to become amber. (Insects or small frogs may be preserved in amber.) Preservation in oily, tar-like asphalt. (Example: Mammals preserved in the LaBrea tar pits in Los Angeles, California). Carbonized imprints of soft-bodied animals like jellyfish in fine-grained sediment.

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KEY PEOPLE Niels Stenson “Nicholaus Steno” Abraham Warner James Hutton William “Strata” Smith Sir Charles Lyell Charles Darwin

Niels Stenson “Nicholaus Steno” ( ) Formulated 3 Principles 1.Superposition 2.Original Horizontality 3.Original Lateral Continuity These 3 principles are the basis of Stratigraphy

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f02_04_pg14 Principal of Original Horizontality

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

f02_06_pg15 Principal of Original Lateral Continuity

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 1.Core of mountains formed from a hot water ocean of dissolved minerals. 2.Subsidence of ocean & deposition of fossil- bearing rock. 3.A top layer of transition rocks – sandstones, shales, coal beds, fossiliferous limestones and old lava flows.

Abraham Werner Problems With Theory 1.What happened to the immense volume of water that covered the Earth. 2.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) coined 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 1.Disconformity 2.Nonconformity 3.Angular Unconformity

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

Catastrophism (Baron Georges Leopold Cuvier – ) 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 – ) 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 – ) 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”

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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THE END