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FirstLook - GG 103 Goals GG • To present knowledge that...

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Unformatted text preview: GG 103 Goals GG • To present knowledge that will be useful for life, whether forming opinions on environmental issues, selecting a home site or other property, evaluating a business, or deciding on a candidate, or understanding how our Earth works, or just appreciating our beautiful Earth. • To prepare you to consider many environmental issues facing society and Hawaii, such as resource utilization, water use and conservation, and land-use planning. • *** Use the CD. It is very good!!*** Scientific principle: Scientific The universe is sensible and The governed by unchangeable rules. rules. Think about what this means! WHAT IS GEOLOGY? • logia (study) of the geo logia (earth) (earth) HOW DO WE STUDY IT? • directly & indirectly using directly the scientific method scientific What are the tools used in Geology? What Observational (DIRECT): maps rock types, distributions, structures microscopic investigations Experimental (INDIRECT): chemical geophysical The problem of experiments The Since geologists are interested in systems that are very big (hundreds of km) and that have evolved over long periods of time (millions of years), they cannot conduct controlled experiments. They must observe the results of Nature’s experiments that are already complete or “in the works”. The scientific method The 1) Make an observation about the sensible world. 2) Develop an explanation (hypothesis) that predicts the outcome of other observations or experiments. The scientific method (cont.) The 3a) Make new experiments. 3b) Make new observations. The scientific method (cont.) The return to step 2 Reject the hypothesis no 4) Do the results match the predictions of the hypothesis ? return to step 3 yes Hypothesis -> Theory -> Law Hypothesis A hypothesis is an explanation initially offered for a set of observations. When a hypothesis withstands many tests it may be called a theory. A theory for which there seem to be no sensible reasons to challenge is called a law. We study Earth to figure out how it works! • resources • environment • hazards • • • • • RESOURCES HAZARDS BEAUTY ENVIRONMENT Geology in the News Earthquakes in Iran Mud slides in California Just on O`ahu: rain problems Mudslides Sewage spills Runoff (flooding) Falling rocks Geology of the Hawaiian Islands Concentrate on volcanic geology Plenty of terminology, but we need it to communicate Introduced to Physical Geology as applied to the Hawaiian Islands “+” including natural & human-induced hazards 2 MAJOR CONCERNS • GEOLOGIC TIME • ENERGY TIME Geology is a science......just like chemistry and physics! But geologists face the special challenge of not being able to do experiments in the sense that chemists and physicists do. TIME The big difference between geology and other sciences is that not much happens geologically in a human lifetime! Rates of geologic processes: ~ cm/year cm/year Big earthquakes may displace the ground several meters in a few seconds, but they occur only every 500 years or so. TIME The rates of geologic processes are almost always slower than the rates of human effects on the environment. Geologists use millions of years as the standard unit of time: Ma = million years ago m.y. = an interval of time (million years) MAN & GEOLOGIC TIME (ARISTOTLE - EARTH CENTERED) FAST TIME BISHOP USSHER CATASTROPHISM WORLD-WIDE & SUDDEN DISASTERS SLOW TIME JAMES HUTTON UNIFORMITARIANISM THE PRESENT IS THE KEY TO PAST Siccar Point, Scotland Some geologic features take millions of years to form. Carr Clifton Others take seconds! John Sanford/Photo Researchers Scientific principle: Scientific The universe is sensible and The governed by unchangeable rules. rules. What does this mean? IT MEANS IT James Hutton’s Uniformitarianism “The present is the key to the past” i.e. Natural laws do not change — Natural however, rates and intensity of processes do. processes Geologic Time Scale Geologic Geologic Geologic Time Scale Scale ENERGY GIANT MACHINE (EARTH) DRIVEN BY 2 HEAT ENGINES: EXTERNAL ENGINE INTERNAL ENGINE [CD: External Processes, external v. [CD: internal] internal] EXTERNAL ENGINE - SUN 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 & DEPOSITION! 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 UNIVERSE BIG BANG UNIVERSE UNIVERSE COMPOSED OF HYDROGEN (76%) HELIUM (23%) ALL ELSE (1%) THE SOLAR SYSTEM THE SOLAR NEBULAR SOLAR FORMED 4.55 BILLION YEARS AGO AS YEARS PLANETESIMALS COALESCED INTO PLANETS PLANETS 4 INNER ROCKY INNER PLANETS AND 4 GAS GIANTS + PLUTO GIANTS HEATED BY IMPACTS HEATED OF NUBULAR DEBRIS OF CAUSING PLANETS TO CAUSING DIFFERENTIATE DIFFERENTIATE The origin of the solar system. A catastrophic impact between the proto-Earth and a Mars-sized impactor made the moon. Heating and differentiation of the early Earth. EARTH - OUR ISLAND HOME EARTH The Three States of Water (Why Earth is so special) STRUCTURE OF EARTH [CD: A 1-2] OK! SO WHAT? WE HAVE ALL THIS INFORMATION BUT HOW DOES EARTH WORK? PLATE TECTONICS!!! PLATE TECTONICS • UNIFYING THEORY of plate motion • PLATES (same as lithosphere) - 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 • [CD: INTERNAL, PLATE TECTONICS] 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 sub-marine volcanic mountains SUBDUCTION & COLLISION MARGINS where subducting plates move into Earth’s interior. Oceanic crust is SUBDUCTED & destroyed. Continental crust COLLIDES and builds mountains. SUBDUCTION QuickTime ™ and a GIF decompressor are needed to see this picture. TRANSFORM MARGINS •Plates slide horizontally past each other at great vertical faults •Plates scrape & deform margins as they move •Crust is neither created nor destroyed SYSTEMS - Run by energy & made of energy matter matter 1. Definition: ANY PORTION OF THE UNIVERSE Definition: SEPERATED FROM THE REST OF THE UNIVERSE FOR THE PURPOSE OF OBSERVING CHANGES 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 Systems SUBSYSTEMS are in DYNAMIC BALANCE DYNAMIC Kinds of Systems Kinds Earth is a Closed System with 4 subsubsystems CYCLES - Group of processes that CYCLES move matter and energy between subsystems 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 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 ...
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