Chapter 1. Introduction. Introduction Geology. Introduction. Earth Systems. Earth Systems. Understanding Earth (Earth systems)

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1 Chapter 1 Understanding Earth (Earth systems) A Dynamic and Evolving Planet Introduction Geology Geology is the study of the earth, a complex, integrated system of related parts, components, or subsystems that interact in an organized fashion, affecting one another in various ways. Introduction The systems of the earth include the: Atmosphere Biosphere Hydrosphere Lithosphere Mantle (plate tectonics) Core (geodynamo & geomagnetics) Introduction The interaction of these subsystems has resulted in a dynamically changing planet in which matter and energy are continuously recycled into different forms. Earth Systems Climate system (how, why, etc) 1. Weather, complex, unable to predict with accuracy beyond week or so 2. Climate = weather over time, general predictions, 3. System driven by sun; interaction with ocean/land, atmosphere, earth rotation/tilt, etc, plus interference due pollution, volcanic dust, etc (geology) Earth Systems Plate Tectonics (theory/geological model) 1. Combines volcanism, earthquakes, shape of continents, seafloor surface, etc 2. Driven by convection within earth mantle due to internal heat, radiation, 3. Affects lithosphere, crust & outer mantle (depth to 100 km) and asthenosphere (plastic layer within mantle) 1

2 Earth Systems Plate Tectonic: Driving force similar to boiling pot of water The plate tectonics system: : how does the heat energy inside the Earth move and thus affect the crustal plates? Convection causes hot water to rise...where it cools, moves laterally, sinks, Hot matter from the mantle rises, causing plates to form and diverge. Plate Plate Where plates converge, a cooled plate is dragged under warms, and rises again. sinks, warms, and rises again. The geodynamo system: : rapid motion of the liquid outer core stirs up electrical flow in the solid (iron) inner core causing Earth s s magnetic field What is geology? Geology is the study of the Earth. Physical geology is concerned with the materials and processes which compose and operate on the surface of, and within, Earth. Historical geology is concerned with the origin and evolution of Earth's continents, oceans, atmosphere, and life. 2

3 Geologists are employed in diverse occupations. Principle occupations include: Mineral and energy resource exploration Solving environmental problems Predicting natural disasters What is geology? Geology and the Formulation of Theories What is a theory? It is arrived at through the scientific method, which involves gathering and analyzing facts formulating hypotheses to explain the phenomenon testing the hypotheses and finally proposing a theory. The hypotheses is a tentative explanation. A scientific theory is a testable explanation for some natural phenomenon, that is supported by a large body of evidence. Scientific method: Steps 1. Observation/Experimentation ->someone develops tentative explanation -> becomes hypothesis Scientific method: 2. Hypothesis -> presentation (publication or abstract/presentation verbally) to peers 3. Peers challenge hypothesis - If passes challenge then several hypotheses may form theory 4. Theory (-> presentation) - Challenge to theory 5. Scientific model (combine theories with hypotheses) The scientific method in Geology the goal: is to explain how the universe works How Does Geology Relate to the Human Experience? Geology pervades our everyday lives and is a part of many aspects of human experience, including the arts and literature. The range of environmental problems and issues of concern to society require a basic understanding of geology. 3

4 How does geology affect our daily lives? Natural Events Economics and Politics Our Role as Decision makers Consumers and Citizens Sustainable Development Discussion: product source Global Geologic and Environmental Issues Facing Humankind Most scientists would argue that overpopulation is the greatest problem facing the world today. Increasingly large numbers of people must be fed, housed, and clothed, with a minimal impact on the environment. Global Geologic and Environmental Issues Facing Humankind The greenhouse effect is the retention of heat in the atmosphere, which results in an increase in the temperature of Earth s surface and atmosphere, thus producing global warming. Origin of the Universe Did it begin with a Big Bang? In the Big Bang theory, the universe began approx. 14 billion years ago (13.7 Ga). At that time an extremely compressed, dense, hot body of matter exploded, began to expand and is now cooling Origin of the Universe How do we know? Evidence for the Big Bang: Evidence: universe Motion to left causes waves to have shorter wavelength on left and longer on right Example: siren on car moving to left is higher pitch on left and lower on right side is expanding from a central point. 1. Doppler effect: the spectral line (wavelengths of galaxy light) shifts to red end (longer wavelength) due the expansion of galaxies. Origin of the Universe How do we know? Evidence for the Big Bang: 1. Doppler effect 2. Background 1. Doppler effect: red & blue shift 2. Radiation so temperature is 2.7 degrees above absolute zero ( C) or C where it should be at absolute zero radiation: The entire universe has a pervasive and constant background radiation, thought to be the faint afterglow of the Big Bang. 4

5 Origin of Solar system Origin of Solar system Solar System: The nebular hypothesis (4.6 Ga) ) Immanuel Kent, German 1755 Summary 1. the sun forms (rotating cloud gas & dust, compact, ignite, fusion =>proto-sun (early sun)) 2. the planets form planetesimals (hot gases cool to these, crash together to form terrestrial planets) inner rocky planets (terrestrial) V, M, E, M outer jovian planets (gas & ice) J, S, U, N Origin of Solar system Origin of Solar system Origin of Solar system Origin of the solar system Small bodies of the solar system Asteroids (between Mars & Jupiter, 300 with dia.>100km, 10,000 with diameter>10km) Meteorities small pieces of asteroids, probably similar formation, left overs Comets ice and dust, located in outer reaches of solar nebula 5

6 Our Solar System Its Origin and Evolution The Solar System formed from a rotating cloud of interstellar matter about 4.6 billion years ago This cloud, upon condensing, collapsed under the influence of gravity and flattened into a rotating disk. The sun, planets, and moons formed within this disk. Earth Its Place in Our Solar System Earth formed from a swirling eddy of nebular material 4.6 billion years ago, accreting as a solid body and soon thereafter differentiated into a layered planet during a period of internal heating. Earth is composed of 3 concentric layers. Earth has continuously changed during its 4.6 billion year existence as a result of interactions between its various subsystems and cycles. Core Mantle Crust. The Core The Mantle The core consists of a small, solid inner region a larger, liquid, outer portion Composed of iron and a small amount of nickel. The mantle surrounds the core and is divided into: a solid lower mantle an asthenosphere that behaves plastically and flows slowly a solid upper mantle. Composed primarily of peridotite, an igneous rock made of olivine. 6

7 The Crust The Asthenosphere The outermost layer, the crust, is divided into: thick continental crust thin oceanic crust Surrounds the lower mantle Behaves plastically and slowly flows Partial melting in the asthenosphere generates magma (molten rock) that rises to the earth s surface. The Lithosphere Plate Tectonic Theory The crust and upper mantle make up the lithosphere which forms the solid outer layers of the Earth. The lithosphere is composed of rigid plates that diverge, converge, or slide sideways past one another as they move over the asthenosphere Plate Tectonic Theory Plate Tectonic Theory Volcanoes and earthquakes occur at the boundaries between the plates. 7

8 Plate Tectonic Theory Plate tectonic theory is a unifying explanation for many geologic features and events, helping us understand the composition and internal processes of Earth on a global scale. The Rock Cycle A rock is a solid aggregate of one or more minerals, as well as non-crystalline matter such as natural glass or organic material like coal. There are three major groups of rocks Igneous Sedimentary Metamorphic The Rock Cycle Igneous Rocks form from the crystallization of magma as it cools or the consolidation of volcanic ejecta. The Rock Cycle Sedimentary Rocks are typically deposited in layers formed from: Granite Intrusive Igneous Rock Intrusive igneous rock crystallizes beneath the earth s surface. Extrusive igneous rock crystallizes and cools at the earth s surface. At times it cools so fast that it forms a glass or ash. rock/mineral fragments precipitation of minerals from solution the compaction of plant and animal remains. Basalt Extrusive Igneous Rock Conglomerate Forms from river gravels Limestone Precipitation from seawater The Rock Cycle Metamorphic Rocks form from alteration of other rocks, usually by: The Rock Cycle The rock cycle illustrates the interactions between Earth s internal and external processes and how the three rock groups are interrelated. Heat Pressure Chemically active fluids Gneiss Quartzite 8

9 The Rock Cycle How are the rock cycle and plate tectonics related? Organic Evolution and the History of Life The theory of organic evolution states: Plate movement is the driving mechanism of the rock cycle. Plate interaction determines, to some extent, which of the three rock groups will form. that all living things are related and have descended with modification from organisms living in the past. Charles Darwin proposed that the mechanism of natural selection results in survival reproductive age of those organisms best suited to their environment. Fossils, the remains of once-living organisms provide the evidence for evolution and a history of life before humans. Organic Evolution and Plate Tectonics Together the theories of plate tectonics and organic evolution have changed the way we view our planet. Geologic Time An appreciation of the immensity of geologic time is central to understanding the evolution of the Earth and its life. Geologic time differs from the human perspective of time Earth goes through cycles of much longer duration than the human perspective of time The immense span of time encompassed by the Earth's existence and geological processes sets geology apart The geologic time scale is the calendar that geologists use to date past events in Earth s history. Geologic Time and Uniformitarianism Uniformitarianism forms a cornerstone of geology. It is a fundamental tenet of geology. This principle states that the laws of nature have remained unchanged through time and thus, that the processes observed today have also operated in the past, though possibly at different rates. Therefore, to understand and interpret geologic events from evidence preserved in rocks, geologists must first understand present-day processes in rocks. How does the study of geology benefit us? Understanding how the Earth s subsystems work will help ensure the survival of the human species. It will help us to understand how our actions affect the delicate balance between these systems. 9

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