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Lecture 2 Introduction to Physical Geology Physical Geology Lecture Outline I II Geological Paradigms Origins III Fundamental Concepts of Physical Geology IV V A) B) The Solar System The Earth A) B) Geologic Time The Earth's Structure C) i. ii. Earth's Layers Plate Tectonics - From Continental Drift to Plate Tectonics Lithospheric Plates Plate Boundaries The Rock Cycle Planetary Geology Conclusions Physical Geology Geological Paradigms paradigm, n: a collection of beliefs shared by scientists; a set of agreements about how problems are to be understood James Ussher (1581-1656) catastrophism James Hutton (1726-1797) uniformitarianism rock cycle Charles Lyell (1797-1875) geologic time Alfred Wegener (1880-1930) continental drift Palomar Observatory Physical Geology Origin of the Solar System The Nebular Hypothesis Physical Geology Origin of the Solar System The Nebular Hypothesis painting by W illiam K. H artmann Physical Geology Origin of the Solar System The Nebular Hypothesis gravity physical collision clumps of dust grains (cm) Planetesimals (km) planetesimals (10-100 km) protoplanet (100-1000km) Physical Geology The Solar System What is a Planet? (1) A “planet”1 is a celestial body that (a) is in orbit around the Sun, (b) has sufficient mass for its selfgravity to overcome rigid body forces so that it assumes a hydrostatic equilibrium (nearly round) shape, and (c) has cleared the neighbourhood around its orbit. (2) A “dwarf planet” is a celestial body that (a) is in orbit around the Sun, (b) has sufficient mass for its selfgravity to overcome rigid body forces so that it assumes a hydrostatic equilibrium (nearly round) shape2 , (c) has not cleared the neighbourhood around its orbit, and (d) is not a satellite. (3) All other objects3 except satellites orbiting the Sun shall be referred to collectively as “Small Solar-System Bodies”. Physical Geology Origin of the Earth Geological Differentiation Earth melted by: gravitational energy left from formation of planet meteor bombardment radioactive decay Gravity concentrated denser materials (Ni & Fe) in center Less dense materials (silicates) forced to outer layers Crust became stable after 1 billion years Compositional Zones Crust Continental Oceanic Mantle Core Outer (Liquid) Inner (Solid) Physical Geology Fundamental Concepts Earth's Layers Compositional Zones Core Solid inner core Liquid outer core Radius of ~3500 km 16.2% of Earth's vol. 31.5% of Earth's mass Generates Earth's magnetic field Mantle Thickness ~2900 km 82.3% of Earth's vol. 67.8% of Earth's mass Crust Oceanic – 4-20km thick Continental – 30-70km thick Mechanical Zones Core Mesosphere Lower mantle Rigid Very Hot Capable of gradual flow Asthenosphere "weak" layer Convecting mantle Soft and readily flows Lithosphere Crust and Upper Mantle Rigid Brittle Physical Geology Fundamental Concepts Geologic Time Divisions Eon Era Period Epoch Age Phanerozoic Eon Paleozoic Era Mesozoic Era Cenozoic Era -"Eon of Evident Life" -"Era of Old Life" -"Era of Middle Life" -"Era of Modern Life" Physical Geology Fundamental Concepts Plate Tectonics - The Evidence Physical Geology Fundamental Concepts Plate Tectonics - The Ocean Floor Mid-Ocean Ridge System Physical Geology Fundamental Concepts Plate Tectonics - The Ocean Floor Mid-Ocean Ridge System underwater mountain range 80,000 km long 1500-2500 km wide up to 3000 m above sea floor rift valley, 1-2 km deep, runs along axis 4000 km wide fracture systems Physical Geology Fundamental Concepts Plate Tectonics - The Ocean Floor magnetic striping crustal age Physical Geology Fundamental Concepts Plate Tectonics - The Ocean Floor Physical Geology Fundamental Concepts Plate Tectonics - The Engine Physical Geology Fundamental Concepts Plate Tectonics - Lithospheric Plates Physical Geology Fundamental Concepts Plate Tectonics – Plate Boundaries Physical Geology Fundamental Concepts The Rock Cycle Atmospheric Processes Weathering Physical Weathering Chemical Weathering Biological Weathering Sediment Transport Lithospheric Processes Burial Compaction and Cementation Heat and Pressure Stress Plate Tectonics Exposure Physical Geology Planetary Geology Venus Europa Jupiter Magellan Galileo Mars Io Galileo Viking 1 Voyager 1 Physical Geology Planetary Geology Mars