Geo. 101 – 1st Edition Lecture 3 Outline of Last Lecture I. Rock TypesII. Formationsa. The Earthb. The MoonOutline of Current Lecture I. Plate Tectonic Theorya. Continental Drift HypothesisII. Plate Boundariesa. DivergentCurrent LecturePlate Tectonic Theory:- Alfred Wegner (1915):o Creator of the Continental Drift Hypothesis (Pangea)o His evidence: Continents fit together like a puzzle Animals are found on multiple continents (they can’t cross oceans) Fossil Evidence found on multiple continents- Related rock types- Historically similar climateso Wegner lacked a mechanism for the shifting of the continents.o Remained a hypothesis because he couldn’t explain the force of movement- Geodynamo:o Flows in the core creates a magnetic field, which reverses every ½ million yearso Shown in the magnetic stripping on the ocean floor.- 4 Concepts of the Plate Tectonic Theory:1. The outer portion (lithosphere) is broken up into units called platesa. Twelve total plates2. The plates are in motion; they act as rigid units that ride along the asthenosphere (which is moving).3. Most geologic activity happens near the plate boundaries.These notes represent a detailed interpretation of the professor’s lecture. GradeBuddy is best used as a supplement to your own notes, not as a substitute.4. Plate Interiors are relatively quiet.o EVIDENCE: Earthquakes/Volcanoes occur near continent edges.Boundaries:o Divergent: These boundaries occur when plates move away from each other.o Convergent: These boundaries occur when plates move together.o Transform: These boundaries occur when plates move laterally next to each other.o Hot Spot: This is a stationary thermal plume burning beneath the crust that pushes up and out.- Divergent Boundaries: (tension)o Plates move away in the process of rifting. Rift: A crack-like valley which allows molten rock to erupt from below. Sea Floor Spreading: New oceanic lithosphere EX: Mid-Atlantic Ridge, Iceland, Sea of Cortez (Gulf of California)o Decompression Melting: As hot mantle material rises, the drop in pressure results in melting
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