Transcript Chapter 1
WELCOME TO GG 101 PHYSICAL GEOLOGY My name is Patty Lee. We meet Monday , Wednesday and Friday from 10:30 to 11:20. SHOW UP! We will study the PHYSICAL characteristics or the GEOLOGY of our planet, EARTH. WHAT IS GEOLOGY? logia (study) of the geo (earth) HOW DO WE STUDY IT? directly & indirectly using the scientific method WHY DO WE STUDY IT? To figure out how Earth works! resources environment hazards RESOURCES HAZARDS ENVIRONMENT BEAUTY 2 MAJOR CONCERNS GEOLOGIC TIME ENERGY GEOLOGIC TIME ARISTOTLE FAST TIME SLOW TIME BISHOP USSHER JAMES HUTTON CATASTROPHISM UNIFORMITARIANISM WORLD-WIDE & THE PRESENT IS THE SUDDEN DISASTERS KEY TO PAST Siccar Point, Scotland Fig. 1.3 Geologic Time Scale Geologic Time Scale ENERGY GIANT MACHINE (EARTH) DRIVEN BY 2 ENGINES -> HEAT ENGINES: EXTERNAL ENGINE INTERNAL ENGINE EXTERNAL ENGINE - SUN • 60% OF SOLAR ENERGY IS USED TO DRIVE WEATHER SYSTEM BY VARIABLE HEATING • HYDROLOGIC CYCLE -> EVAPORATION • JOB IS TO FLATTEN THE SURFACE OF EARTH BY WEATHERING, EROSION & INTERNAL ENGINE • HEAT FLOWS FROM HIGH TO LOW TEMPERATURE • FROM INSIDE TO OUTSIDE OF EARTH • JOB IS TO BUILD VOLCANOES, MOUNTAINS, MOVES PLATES -> PLATE TECTONICS HOW HEAT WORKS • WORKS IN 2 WAYS -> CONDUCTION & CONVECTION • ROCKS BEHAVE PLASTICALLY (wax, soft tar) • GEOTHERMAL GRADIENT -> ~1deg.C/40M THE UNIVERSE BIG BANG UNIVERSE COMPOSED OF HYDROGEN (76%) HELIUM (23%) ALL ELSE (1%) Hubble DEEP FIELD <origins.jpl.nasa.gov/ poster/ deepfield.html> THE SOLAR SYSTEM SOLAR NEBULAR FORMED 4.55 BILLION YEARS AGO AS PLANETESIMALS COALESCED INTO PLANETS 4 INNER ROCKY PLANERS AND 4 GAS GIANTS + PLUTO HEATED BY IMPACTS OF NUBULAR DEBRIS CAUSING PLANETS TO DIFFERENTIATE The origin of the solar system. A catastrophic impact between the proto-Earth and a Mars-sized impactor. Heating and differentiation of the early Earth. EARTH - OUR ISLAND HOME The Three States of Water (Why Earth is so special) A model of the Earth’s interior. OK! SO WHAT? WE HAVE ALL THIS INFORMATION BUT WHAT DOES IT MEAN? WHAT IS PLATE TECTONICS? LET’S FIND OUT! PLATE TECTONICS • UNIFYING THEORY of plate motion • PLATES - 7 major plates & many minor plates • MOVE with respect to each other as fast as finger nails grow • **remember that crust rides in lithosphere over the asthenosphere** • Three (3) kinds of PLATE MARGINS DIVERGENT MARGIN <-SPREADING-> • Plates move apart leaving a gap that is filled by magma/lava making new sea floor & new plate • Occurs at Divergent Margins (MOR) • Mid-Ocean Ridges (MOR) are elevated submarine volcanic mountains CONVERGENT MARGIN ->SUBDUCTION OR COLLISION<• Deep sea trenches where subducting plates move into Earth’s interior • Oceanic crust is SUBDUCTED, destroyed • Continental crust COLLIDES and builds mountains TRANSFORM MARGINS QuickTime™ and a GIF decompressor are needed to see this picture. • Plates slide horizontally past each other at great vertical faults • Plates scrape & deform margins as they move • Crust is neither created nor destroyed Earthquakes & Plate Margins WHY ALL THIS ACTIVITY? Just what drives the plates? • CONVECTION CURRENTS - transfers heat from inside to surface - plates ride the currents • RIDGE-PUSH - upwelling pressure so great at MOR that forces plates to split • SLAB-PULL - cooled slabs are so heavy that drag plate down a subduction zone-gravity assisted • RIDGE MASS - mass is so great @ MOR that forces plates to move away • MANTLE PLUMES - locally concentrated upwellings, lateral flow, slow downwelling SYSTEMS - Run by energy & made of matter 1. Definition: ANY PORTION OF THE UNIVERSE SEPERATED FROM THE REST OF THE UNIVERSE FOR THE PURPOSE OF OBSERVING CHANGES It is implied that all systems have boundaries The amount of matter in a closed system is fixed! Systems are composed of SUBSYSTEMS which are in DYNAMIC BALANCE Kinds of Systems The Earth is a Closed System CYCLES - Group of processes that move matter and energy between subsystems HYDROLOGIC CYCLE - driven by Sun and works on surface ROCK CYCLE - 3 families defined by formation processes IGNEOUS ROCKS - “born of fire”; melted rock-> MAGMA SEDIMENTARY ROCKS - formed at surface from rock fragments METAMORPHIC ROCKS - altered preexisting rock material TECTONIC CYCLE - moves rock material between surface & Earth’s interior by interaction of tectonic plates; run by internal heat The 3 Major Cycles IRON CATASTROPHY STRUCTURE OF EARTH