101 Geol Scientific Method
Historical Geography Chronology of events
9/13/2007 2:31:00 PM
Past to Present When Dinos walked? Physical Geography Understanding the processes and materials of Earth? How? Why? Rates of Processes Plates o 1-10 cm/yr How do you go about discovering processes? Paths to discovery Curiosity Problems Boredom Hypothesis Scientific Method - (Geologist approach to research and discovery) Steps: o Observe and Measure Earth's Shadow; Ships o Form A Hypothesis (A plausible but unproven, explanation) Earth is Round o Test Hypothesis Compare predictions with new observations If True Then Ex. Sun rays would hit earth parallel o Formulate a Theory A generalization about natural phenomena o Form a Law of Principle Statements that some natural phenomenon is invariable observed to happen in the same way o Reexamine (Most Important) In Class Exercise:
Observation o 1700's Continents fit together Hypothesis o 1858 Continents moved apart (Contenental Drift) Tests o 1960 IF TRUE THEN material near mid-ocean ridge would be younger than material farther away Theory o 1970's Plate Tectonics is accepted by Scientific Community Law Reexamine SCIENTIFIC REVOLUTIONS MOVE SLOW Different Questions/Scenerios Require Modification of the method Field Work o Long standard of geology Seasonal Processes Instrumental/Lab Work Complete of Simulations How rapid are geologic processes? Catastrophism o 1600's and 1700's people believed Earth's Features (mountains, valleys, oceans, rivers) were permanent and had been produce by a few great upheavals James Hutton 1726 1796 `Father of Modern Geology' Observation o Slow erosion and transport of sediments Gradualism counter hypothesis Uniformitarianism Earth Processes move slowly, continuous cycle
Have been operating through out Earth's History Problem: o Rock Cycle (Uplift, erosion, transfer, deposition, solidification, uplift) time Long Accepted 1800's or Early 1900's Modern Earthquakes mirrors events past that built mountains Current Perspectives Early conditions likely differed (temp and chem) Conditions affect rates of processes Catastrophism Obervation o Odd thin rock layer, rich in iridium o Castastrophic impact from a meteor About 66 million yrs ago Mass extinction of dinos occurred at that time Local Catastrophies: o Earthquakes o o o Mass Volcano Eruptions Tsunami's Floods Extinction about 245 million years ago 90% plants and
animals gone Earth is about 4.5 Billion years old Appalachans rose about 300 million years ago Rockies about 70 million years ago Most recent glacial retreat about 12,000 years ago Birth of the Earth Meteorites (and their scars) o Clues to plants formation Growth processes called planetary accretion (snowball effect) o Ongoing process Earth's Inner Structure Meteroite Impacts o Kinetic energy is transformed into thermal energy o Size and temperature increase Radioactive Decay (also adds heat)
Earth o Less-Dense molten materials (Si, Al, Na, K) migrated toward the surface o Dense melted materials in the center o Core Most iron a little nickel o Mantle Slow perpetual motion, behaves like a plastic Dense minerals o Inner Structure Inner Core (5000 Degrees) Solid Iron because it has a very high pressure (despite a very high temperature) Outer Core Layer of molten nickel, iron, and sulfur Mesosphere Between the core and asthenosphere Asthenosphere Mantle rock becomes ductile 100 350 km depth Lithosphere Outer 100 km Rocks are more rigid Crust Lighter minerals Earthquakes Measure the time for earthquake waves to travel through the Earth by different paths Rates tell us about composition Iron Meteorites Dense things that are close to iron on Earth Oceanic thin and dense Continental Thick and less dense
9/13/2007 2:31:00 PM
9/13/2007 2:31:00 PM