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Transcript
Teknologi Dan Rekayasa Mapping And Surveing Department INTRODUCTION The science of Geology Why Geology? Related to our daily life, such as: Water and soil Provide guide to use of natural resources Provide knowledge of avoiding natural hazards Helping protecting the environment • Physical geology : examines Earth materials, understand surface and subsurface processes Geology incorporates principles from physics, chemistry, biology, engineering Teknologi dan Rekayasa The Science of Geology Some historical notes about geology Catastrophism – mid 1600’s, James Ussher Sudden and violent change shape landscapes Religious belief of Earth created in 4004 B.C. Uniformitarianism – late 1700’s, James Hutton processes that operate today also operated in past geologic processes occur over extremely long time birth of modern geology Teknologi dan Rekayasa Earth as a system Earth is a dynamic planet with many interacting parts or spheres Parts of the Earth system are linked Characterized by processes that • Vary on spatial scales from fractions of millimeter to thousands of kilometers • Have time scales that range from milliseconds to billions of years Teknologi dan Rekayasa Earth as a system Powered by Sun - drives external processes • Atmosphere • Hydrosphere • At Earth’s surface Powered by the Earth’s interior • Heat remaining from Earth’s formation • Heat generated continuously by radioactive decay - powers internal processes that produce volcanoes, earthquakes, & mountains Teknologi dan Rekayasa A view of Earth Earth is a planet that is small and selfcontained, fragile, sensitive to change Environment is highly integrated with interactions between air, water, rock, life Earth’s four spheres • Atmosphere- air • Biosphere- life • Hydrosphere - water • Solid Earth- rock Teknologi dan Rekayasa Atmosphere Gaseous environment that surrounds Earth – provides life 90% of atmosphere within 10 miles of Earth surface (thin relative to radius of the solid Earth at 4000 miles) Provides air for breathing and protects from Sun’s heat and ultraviolet radiation Recent concern with atmosphere regarding Ozone holes and Global Warming Teknologi dan Rekayasa Hydrosphere Water makes our “Blue” plant unique –sustains life Water in motion – Hydrologic cycle evaporation from oceans, precipitation from atmosphere, run off back to ocean 97% ocean water, 3% fresh water fresh water includes: surface water (lakes, streams), ground water and glaciers Ocean covers 71% of Earth surface -average depth of 3800 m (12,500 feet) Teknologi dan Rekayasa Earth’s Water Balance Teknologi dan Rekayasa Biosphere Biosphere includes all life (including us!) Extends from ocean floor to several miles into atmosphere; however, concentrated at Earth surface Life responds to countless interaction with the environment Successful adaptation to changing environment – evolution of species Non-successful adaptation – Extinction Survival of the “fittest” – Darwin’s Legacy Teknologi dan Rekayasa Solid Earth Solid Earth: between atmosphere and oceans – rocks and soil Surface and subsurface features reveal dynamic processes – Plate Tectonics Face of the Earth Earth’s Interior Rock cycle - the loop that involves the processes by which one rock type changes to another Teknologi dan Rekayasa The face of Earth Earth’s surface - two principal divisions • Continents • Ocean basins Significant difference between the continents and ocean basins is their relative elevations • • • continents average 2750 feet above msl ocean floor average 12,500 feet below msl continents average 15,250 feet above ocean floor Teknologi dan Rekayasa Continents and Ocean Basins Teknologi dan Rekayasa Continents Mountain belts – linear features, active Youngest Mountains • • Circum-Pacific Belt (surrounds Pacific Ocean) Island arcs – active volcanic mountains, Older mountains • • Appalachian – eastern United States Urals – Russia Shields – continental interiors, stable craton, oldest rocks (4 billion yrs) Teknologi dan Rekayasa Ocean basins Continental shelf – gently sloping platform adjacent to shore Continental slope – steep dropoff from shelf to deep ocean floor Ocean ridge system – most prominent topographic feature on Earth (43,000 mi) Deep-ocean trenches – deep narrow depressions (36,000 feet) Teknologi dan Rekayasa Earth’s internal structure Layers defined by chemical composition Crust – thin, rocky outer skin Mantle – solid, rocky shell Core – iron-nickel alloy center Layers defined by physical properties Lithosphere – sphere of rock Asthenosphere – weak sphere Mesosphere – middle sphere Core – outer (liquid), inner (solid) Earth’s Layered Structure Teknologi dan Rekayasa Layers Defined by Composition Crust • • Oceanic – 7 km thick, dark igneous rock basalt, young (<180 my), dense (3.0 g/cm3) Continental – 70 km thick, granitic rock, old (up to 4000 my), less dense (2.7 g/cm3) Mantle • • contains 82% Earth’s volume, depth 2900 km rock called peridotite, more dense (3.3 g/cm3) • • iron-nickel w/ minor oxygen, silicon, sulfur extreme pressure – highly dense (11 g/cm3) Core Teknologi dan Rekayasa Layers by Physical Properties Lithosphere • • Asthenosphere (upper Mantle) • • soft weak layer, partial melting depth of 660 km Mesosphere (lower Mantle) • • cold, strong rock exhibits rigid behavior 5 to 250 km thick between 660 and 2900 km depth very hot, gradual flow of convection currents Core (differing mechanical strengths) • • Outer – liquid, generates Earth’s magnetic field Inner – behaves as solid due to immense pressure Teknologi dan Rekayasa Earth’s internal structure How do we know about the Earth’s interior? Study of seismic wave generated by earthquakes Chapter 17 Teknologi dan Rekayasa Dynamic Earth The theory of plate tectonics • continental drift – the idea that continents moved about the face of the planet • not widely accepted for more than 50 years because driving mechanism unknown • magnetic patterns on sea floor (found from chasing submarines during WWII) suggested sea floor spreading • Plate Tectonics accepted in 1965 as driving mechanism Teknologi dan Rekayasa Theory of plate tectonics Symmetric magnetic pattern around ocean spreading ridges Black: north magnetic pole, white south magnetic pole New ocean crust records magnetic pole Crust moves away from spreading ridges Teknologi dan Rekayasa Plate Tectonics Earth’s rigid outer shell composed of numerous slabs (plates) • mobile, continually changing size and shape • create, consume, transform lithosphere Plate boundaries • Most major interactions among individual plates occurs along their boundaries Plate tectonics – first comprehensive model of Earth’s surface and internal workings Teknologi dan Rekayasa Plate Boundaries Divergent – two plates move apart, resulting in upwelling of material from the mantle to create new seafloor Convergent – two plates move together with subduction of oceanic plates or collision of two continental plates consuming old lithosphere Transform – located where plates grind past each other without either generating new lithosphere or consuming old lithosphere Teknologi dan Rekayasa Mosaic of Earth’s Outer Shell Teknologi dan Rekayasa Plate Boundaries Teknologi dan Rekayasa Divergent Boundaries Plate spreading – occurs mainly at mid-ocean ridges (sea floor spreading), rate of 2 to 20 cm/yr Molten rock rises from asthenosphere through fractures (cracks) in hard rock, encounters sea water, cools to new rock. New ocean crust is continually created – oldest ocean floor rock is 180 million years. Teknologi dan Rekayasa Convergent Boundaries Older ocean plates consumed by subduction zone and returned to mantle One plate descends beneath another – high temperature, high pressure environment producing molten rock Pacific “ring of fire” – volcanic chains result in explosive eruptions Mount Saint Helens, WA – 1980 Mount Pinatubo, Philippines – 1991 Teknologi dan Rekayasa Transform Fault Boundaries Plate grind past each other without creating or consuming lithosphere San Andreas Fault Zone, CA – Pacific plate moving northwest relative to North American plate Capable of producing strong earthquakes • Loma Prieta, San Francisco, CA in 1989 – 7.4 • Northridge, Los Angeles, CA in 1994 – 6.7 Teknologi dan Rekayasa Plate Collisions formed the Himalayas Teknologi dan Rekayasa Geologic time Geologists today - accurate dates to geologic events in Earth history Relative dating and geologic time scale • Relative dating – events dates in sequence or order without knowing their age in years • Law of superposition – oldest sedimentary rock layer on bottom • Principle of fossil succession – fossils appear in a definite order, represent time period Absolute (radiometric) dating – Chapter 8 Teknologi dan Rekayasa Geologic time The magnitude of geologic time • Age of Earth – 4.5 billion yrs (4500 million) • Humans arrived – 0.01 million yrs • Count one year per second 24/7– take 150 yrs (two lifetimes) to reach 4.5 billion yrs An appreciation for the magnitude of geologic time is important • many geologic processes are very gradual • we are just a fraction of Earth’s history Teknologi dan Rekayasa Geologic Time Scale Teknologi dan Rekayasa Teknologi dan Rekayasa