* Your assessment is very important for improving the workof artificial intelligence, which forms the content of this project
Download Historical Geology - FacultyWeb Support Center
Survey
Document related concepts
Geochemistry wikipedia , lookup
Paleontology wikipedia , lookup
Schiehallion experiment wikipedia , lookup
Geomorphology wikipedia , lookup
Spherical Earth wikipedia , lookup
History of geomagnetism wikipedia , lookup
History of Earth wikipedia , lookup
Plate tectonics wikipedia , lookup
Large igneous province wikipedia , lookup
History of geodesy wikipedia , lookup
Future of Earth wikipedia , lookup
Transcript
Text: Physical Geology 4th edition by Wicander and Monroe Chapter 1 The Dynamic and Evolving Earth This class is about Physical geology What is Geology? • From the Greek – geo (Earth) logos (reason) • Geology is the study of Earth • Physical geology studies Earth materials, – such as minerals and rocks – as well as the processes operating within – and on Earth’s surface The Role of the Geologist To understand and define: -The structure and composition of the earth -All facets of magma, lava, and volcanic activity -Minerals and rock types -Surface processes: rivers, streams, glaciers, etc. -The earth’s past: both structure origin and life’s evolution with -- Paleontological investigations (studying fossil remains) -Geologic features of other planets Also: -To use information learned to find fossil fuels and ores -To learn how to preserve the environment: erosion control, pollution control -Geologic information ties in greatly with advances in Physical Geology – centered around the Chemical and Physical aspects of the earth • • • • • • • • • • • • • Geochemistry – the chemical makeup of magma, lava, minerals, rocks, etc. Mineralogy – the study of the chemical makeup and occurrence of minerals Petrology – the study of the formation of rocks (which are comprised of minerals) Vulcanology - the study of volcanics Seismology – the study of seismic (earthquake) waves Seismic Tomography – the study of the interior of the earth indirectly by studying the behavior of seismic waves Tectonics – the study of the formation of the continental plates and the mechanics of their movements Oceanography – the study of the chemical and physical aspects of the earth’s oceans Glaciology – the study of the cause and occurrence of glacial episodes Weathering & Erosion –the disintegration or physical and chemical breakdown and subsequent transportation of earth materials Geomorphology – the study of the creations of landforms Soil Sciences – the study of the formation of the various soil types of the world Economic Resources – the study of the formation and usage of natural resources: petroleum, natural gas, coal, stone materials, etc. Scientific Method • The scientific method – an orderly and logical approach – Gather and analyze facts or data • A hypothesis is a tentative explanation – to explain observed phenomena • Scientists make predictions using hypotheses – based upon Observations – then they Test the predictions • After repeated tests, – if one hypothesis continues to explain the phenomena, – scientists propose it as a theory (Conclusions) Formulation of Theories Theory • colloquial usage - speculation or conjecture • scientific usage – coherent explanation for one or several related natural phenomena – supported by a large body of objective evidence Origin of the Universe • The Big Bang – occurred 15 billion years ago – and is a model for the beginning of the universe – Age of Earth= 4.5 Billion years old Solar System Configuration Earth is a Dynamic and Evolving Planet • Changes in its surface • Changes in life Earth is a System of Interconnected Subsystems • • • • • Atmosphere (air and gases) Hydrosphere (water and oceans) Biosphere (plants and animals) Lithosphere (Earth’s rocky surface) Interior (mantle and core) Plate Tectonic Theory • Lithosphere is broken into individual pieces called plates • Plates move over the asthenosphere – as a result of underlying convection cells Geologic Time Scale Summary • Earth is a system – of interconnected subsystems • Geology is the study of Earth • Historical geology is the study – of the origin and evolution of Earth • Scientific method is – – – – an orderly, logical approach to explain phenomena, using data, formulating and testing hypotheses and theories • Universe began with – a big bang 15 billion years ago Summary • Solar system formed 4.6 billion years ago – by condensation and gravitational collapse – of a rotating interstellar cloud • Earth formed 4.6 billion years ago – as a swirling eddy in the solar system nebula • Moon may have formed – when a planetesimal collided with Earth – 4.6 to 4.4 billion years ago • Earth probably started solid – then differentiated into layers – as it heated and melted Summary • Earth’s layers mostly solidified – – – – into the core, mantle and crust, with the upper mantle and crust making up the soft asthenosphere and the solid lithosphere • Lithosphere is broken into plates – that diverge, converge and – slide sideways past each other • Plate tectonics is a unifying theory – that helps explain features and events – including volcanic eruptions, – earthquakes and mountain forming Summary • Central thesis of organic evolution is – that all living organisms evolved – from organisms that existed in the past • An appreciation – of the immensity of geologic time – is central to understanding Earth’s evolution • Uniformitarianism holds that the laws – of nature have been constant through time • Geology is part of our lives – and our standard of living depends – on our use of natural resources – that formed over billions of years Interactions in Earth’s Subsystems Gases from respiration Transport of seeds and spores Interactions in Earth’s Subsystems Wind erosion, transport of water vapor for precipitation Mountains divert air movements Interactions in Earth’s Subsystems Source of sediment and dissolved material Water and glacial erosion, solution of minerals Historical Geology (next semester) • In historical geology we study – changes in our dynamic planet – how and why past events happened – implication for today’s global ecosystems • Principles of historical geology – not only aid in interpreting Earth’s history – but also have practical applications • William Smith, an English surveyor/engineer – used study of rock sequences – to help predict the difficulty of excavation – in constructing canals Evidence for the Big Bang • Universe is expanding • How do we determine the age? – measure the rate of expansion – backtrack to a time when the galaxies – were all together at a single point • Pervasive background radiation of 2.7º above absolute zero – is the afterglow of the Big Bang Big Bang Model • Initial state: – No time, matter or space existed • There is no “before the Big Bang” – Universe consisted of pure energy • During 1st second: – Very dense matter came into existence – The four basic forces separated • gravity, electromagnetic force, 2 nuclear forces – Enormous expansion occurred Big Bang Model (cont.) • 300,000 years later: – atoms of hydrogen and helium formed – light (photons) burst forth for the first time • During the next 200 million years: – – – – Continued expansion and cooling Stars and galaxies began to form Elements heavier than hydrogen and helium began to form within stars by nuclear fusion Features of Our Solar System • • • • • In a spiral arm of the Milky Way Galaxy Sun 9 planets 101 known moons (satellites) a tremendous number of asteroids – most orbit the Sun between the orbits of Mars and Jupiter • millions of comets and meteorites • interplanetary dust and gases Relative Sizes of the Sun and Planets Origin of Our Solar System Solar nebula theory • cloud of gases and dust • formed a rotating disk • condensed and collapsed due to gravity • forming solar nebula – with an embryonic Sun – surrounded by a rotating cloud Embryonic Sun and Rotating Cloud • Planetesimals have formed – in the inner solar system, – and large eddies of gas and dust – remain far from the protosun The Planets • Terrestrial Planets – – – – Mercury Venus Earth Mars • small, composed of rock, with metal cores • Jovian Planets – – – – Jupiter Saturn Uranus Neptune • large, composed of hydrogen, helium, ammonia, methane, relatively small rocky cores Earth’s Very Early History • Started out cool about 4.6 billion years ago – probably with uniform composition/density • Mostly: – silicate compounds – iron and magnesium oxides • Temperature increased. Heat sources: – meteorite impacts – gravitational compression – radioactive decay • Heated up enough to melt iron and nickel Earth’s Differentiation • Differentiation = segregated into layers of differing composition and density • Early Earth was probably uniform • Molten iron and nickel sank to form the core • Lighter silicates flowed up to form mantle and crust Forming the Earth-Moon System • Impact by Mars-sized or larger planetesimal with young Earth – 4.6 to 4.4 billion years ago – ejected large quantity of hot material, – and formed the Moon Forming the Earth-Moon System • Most of the lunar material – came from the mantle of the colliding planetesimal • The material cooled – and crystallized – into lunar layers Forming the Earth-Moon System • Most of the lunar material – came from the mantle of the colliding planetesimal • The material cooled – and crystallized – into lunar layers Moon • Light-colored areas are lunar highlands – Heavily cratered • Provide striking evidence – of massive meteorite bombardment Earth—Dynamic Planet • Earth was also subjected – to the same meteorite barrage – that pock-marked the Moon • Why isn’t Earth’s surface also densely cratered? – Because Earth is a dynamic and evolving planet – Craters have long since been worn away Earth’s Interior Layers • Crust - 5-90 km thick – continental and oceanic • Mantle – composed largely of peridotite – dark, dense igneous rock – rich in iron and magnesium • Core – iron and a small amount of nickel Earth’s Interior Layers • Crust - 5-90 km thick – continental and oceanic • Lithosphere – solid upper mantle and crust • Mantle – composed largely of peridotite – dark, dense igneous rock – rich in iron and magnesium • Core – iron and a small amount of nickel • Asthenosphere – part of upper mantle – behaves plastically and slowly flows Earth’s Interior Layers • Lithosphere – solid upper mantle and crust – broken into plates that move over the asthenosphere • Asthenosphere – part of upper mantle – behaves plastically and slowly flows Earth’s Crust • outermost layer • continental (20-90 km thick) – density 2.7 g/cm3 – contains Si, Al • oceanic (5-10 km thick) – density 3.0 g/cm3 – composed of basalt Modern Plate Map Plate Tectonic Theory • At plate boundaries – Volcanic activity occurs – Earthquakes occur • Movement at plate boundaries – plates diverge – plates converge – plates slide sideways past each other Plate Tectonic Theory • Types of plate boundaries Divergent Mid-oceanic plate ridge boundary Transform plate boundary Continentalcontinental convergent plate boundary Continentaloceanic convergent plate boundary Divergent plate boundary Trench Oceanicoceanic convergent plate boundary Plate Tectonic Theory Influence on geological sciences: • Revolutionary concept – major milestone • comparable to Darwin’s theory of evolution in biology • Provides a framework for – interpreting many aspects of Earth on a global scale – relating many seemingly unrelated phenomena – interpreting Earth history Solid Earth Plate tectonics is driven by convection in the mantle and in turn drives mountain building and associated igneous and metamorphic activity Atmosphere Plate Tectonics and Earth Systems Arrangement of continents affects solar heating and cooling, and thus winds and weather systems Rapid plate spreading and hot-spot activity may release volcanic carbon dioxide and affect global climate Biosphere Hydrosphere Plate Tectonics and Earth Systems Continental arrangement affects ocean currents Rate of spreading affects volume of mid-oceanic ridges and hence sea level Placement of continents may contribute to the onset of ice ages Movement of continents creates corridors or barriers to migration, the creation of ecological niches, and transport of habitats into more or less favorable climates History of Life • The fossil record provides perhaps – the most compelling evidence – in favor of evolution • Fossils are the remains or traces – of once-living organisms • Fossils demonstrate that Earth – has a history of life Geologic Time • From the human perspective time units are in – seconds, hours, days, years • Ancient human history – hundreds or even thousands of years • Geologic history – millions, hundreds of millions, billions of years Geologic Time Scale • Resulted from the work of many 19th century geologists who – – – – pieced together information from numerous rock exposures, constructed a sequential chronology based on changes in Earth’s biota through time • The time scale was subsequently dated in years – using radiometric dating techniques Uniformitarianism • Uniformitarianism is a cornerstone of geology – is based on the premise that present-day processes – have operated throughout geologic time • The physical and chemical laws of nature – have remained the same through time • To interpret geologic events – from evidence preserved in rocks – we must first understand present-day processes – and their results • Rates and intensities of geologic processes – may have changed with time How Does the Study of Historical Geology Benefit Us? • Survival of the human species – depends on understanding – how Earth’s various subsystems – work and interact • Study what has happened in the past, – on a global scale, – to try and determine how our actions – might affect the balance of subsystems in the future We “Live” Geology • Our standard of living depends directly on – our consumption of natural resources – resources that formed millions and billions of years ago • How we consume natural resources – and interact with the environment determines – our ability to pass on this standard of living – to the next generation