GEOL4015-CH1 - Resumen Earth: an Introduction to Physical Geology PDF

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Summary

Review on chapter 1 of the eleventh edition of the book. At the end the Checking Concept questions are answered....

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Chapter 1: Geology: The Science of Earth • • • •

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Physical Geology: Examines the materials composing Earth and seeks to understand the many processes that operate beneath and upon its surface. Historical Geology: to understand the origin of Earth and its development through time. Frequently, geology requires an understanding and application of knowledge ad principles from physics, chemistry, and biology. Geology is a science that seeks to expand our knowledge of the natural world and our place in it. Among hazardous Earth processes that geologists study are: o Volcanoes o Floods o Tsunamis o Earthquakes o Landslides § Of course, geologic hazards are natural processes. They become hazards only when people try to live where the processes occur. The global trend toward urbanization concentrates millions of people into megacities, many of which are vulnerable to natural hazards. Geology deals not only with the formation and occurrence of these vital resources but also with maintaining supplies and with the environmental impact of their extraction and use. An alteration to the environment that was intended to benefit society often has the opposite effect. Catastrophism: believed that Earth’s landscapes were shaped primarily by great catastrophes. Features such as mountains and canyons, which today we know take great spans of time to form, were explained as having been produced by unknowable causes that no longer operates. This philosophy was an attempt to fit the rates of Earth’s processes to the then-current ideas on the age of Earth. Uniformitarism: it states that the physical, chemical, and biological laws that operate today have also operated in the geological past. This means that the forces and processes that we observe presently shaping our planet have been at work for a very long time. Thus, to understand ancient rocks, we must first understand present-day processes and their results. This idea is commonly stated as the present is the key to the past. (Hutton’s theory of Earth) Hutton said, “We have a claim of facts which clearly demonstrate… that the materials of the wasted mountains have changed through the rivers”; and further, “There is not one step in all this progress… that is not to be actually perceived”. He then went on to summarize this trough by asking a question and immediately providing the answer: “What more can we require? Nothing but time”. Hutton in his concluding classic 1778 paper published in the “Transactions of the Royal Society of Edinburg”, he stated, “The results, therefore, of our present enquire is, that we find no vestige of a beginning, no prospect of an end”.

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Hypothesis: tentative (or untested) explanation. Theory: a well-tested and widely accepted view that the scientific community agrees best explains certain observable facts. Scientific method: process in which researchers gather facts through observations and formulate scientific hypothesis and theories. Earth is traditionally divided into three major parts: o Hydrosphere – the water portion of the planet o Atmosphere – earth’s gaseous envelope o Geosphere – the solid Earth o Biosphere - the totality of all plant and animal life in our planet. The global ocean is certainly the most prominent feature of the hydrosphere, blanketing nearly 71 percent of Earth’s surface to an average depth of about 3800 meters (12,500 feet). It accounts for about 97 percent of Earth’s water. However, the hydrosphere also includes the freshwater found undergrounds and in streams, lakes and glaciers. The atmosphere is an integral part of the planet, not only providing air that we breath, but also protecting us from the sun’s intense heat and dangerous ultraviolet radiation. The energy exchanges that continually occur between the atmosphere and the earth’s surface and between the atmosphere and space produce the effects we call weather and climate. The geosphere extends from the surface to the center of the planet, a depth of nearly 6400 kilometers (nearly 4000 miles), making it by far the largest of Earth’s four spheres. Systemic science: aims to study Earth as a system composed of numerous interacting parts, or subsystems. System: is a group of interacting, or interdependent, parts that form a complex whole. The universe begins about 13.7 billion years ago with the Big Bang, an incomprehensibly large explosion that sent all matter of the universe flying outward at incredible speeds. Nebular Theory: proposes that the bodies of our solar system evolved from an enormous rotating cloud called solar nebula. o The solar nebula consisted (besides the hydrogen and helium atoms) of microscopic dust grains and the ejected matter of long-dead stars. The two most massive planets are Jupiter and Saturn The order of the planets are o Mercury o Venus o Earth o Mars o Jupiter o Saturn o Uranus o Neptune Earth’s crust o The crust, Earth’s relatively thin, rocky outer skin, is of two different types – continental crust and oceanic crust. Both share the word crust, but the similarity ends there. The oceanic crust is roughly 7 kilometers (5 miles) thick and composed of the dark igneous rock basalt. By contrast, the continental crust averages about 35 kilometers (22miles) thick but may exceed 70 kilometers (40 miles) in some mountains regions such as the Rockies and the Himalayas.

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Earth’s mantle o More than 82 percent of Earth’s volume is contained in the mantle, a solid, rocky shell that extends to a depth of about 2900 kilometers (1800 miles). o The dominant rock type in the uppermost mantle is peridotite, which is richer in the metals magnesium and iron than the minerals found in either the continental or oceanic crust. o The upper mantle extends from the crust-mantle boundary down to a depth of about 660 kilometers (410 miles). The upper mantle can be divided into three different parts. § The top portion of the upper mantle is part of the stronger lithosphere, and beneath that is the weaker asthenosphere. The bottom part of the upper mantle is called the transition zone. o The lithosphere (sphere of rock) consists of the entire crust plus the uppermost mantle and forms Earth’s relatively cool, rigid outer shell. o Beneath this stiff layer to a depth of about 410 kilometers lies a soft, comparatively weak layer known as the asthenosphere (“weak sphere”). o From about 410 kilometers to about 660 kilometers in depth is the part of the upper mantle called the transition zone. o From a depth of 660 kilometers to the top of the core, at a depth of 2900 kilometers (1800 miles), is the lower mantle. Earth’s core o The core is thought to be composed of an iron-nickel alloy with minor amounts of oxygen, silicon, and sulfur – elements that readily form compounds with iron. o The core is divided into two regions that exhibit very different mechanical strengths. The outer core is a liquid layer 2270 kilometers (1410 miles) thick. The inner core is a sphere that has a radius of 1216 kilometers (754 miles). o Despite its higher temperature, the iron in the inner core is solid due to the immense pressure that exists in the center of the planet.

• Minerals are chemical compounds (or some single elements), each with its own composition and

physical properties. • The nature and appearance of a rock is strongly influenced by the minerals that compose it. In addition, a rock’s texture – the size, shape, and/or arrangement of its constituent minerals – also has a significant effect on its appearance, • Geologist divide rocks into three major grousp: o Igneous o Sedimentary o Metamorphic • The rock cycle allows us to view many of the interrelationshops among different parts of the Earth system. o We will begin with magma, molten rock that forms deep beneath Earth’s surface. Over time, magma cools and solidifies. This process, called crystallization, may occur either beneath the surface or, following a volcanic eruption, at the surface. In either situation, the resulting rocks are called igneous rocks. o If igneous rocks are exposed at the surface, they will undergo weathering, in which the day-in and day-out influences of the atmospheric slowly disintegrate and decompose rocks. The materials that result are often moved downslope by gravity before being picked up and transported by any of a number of erosional agents, such as running water, glaciers, wind or waves. Eventually these particles and dissolved substances, called sediment, are deposited. Sediment is usually lithified into sedimentary rock when compacted by the weight of overlying layers or when cemented as percolating groundwater fills the pores with mineral mater. o If the resulting sedimentary rock is buried deep within earth and involved in the dynamics of mountain building or intruded by a mass of magma, it will be subjected to great pressures and/or intense heat. The sedimentary rock will react to the changing environment and turn into the third rock type, metamorphic rock.

• The two principal divisions of Earth’s surface are the continents and the ocean basincs. o Continents are remarkably flats features that have the appearance of plateaus protruding •

above sea level The continental margin is the portion of the seafloor adjacent to major landmasses. It may include the continental shelf, the continental slope, and the continental rise.

CONCEPT CHECKS 1. Name and distinguish the two broad subdivisions of geology. a. Physical Geology – examines the maerials composing Earth and seeks to understand many processes that operate nebeath and upon its surface. b. Historical Geology – to understand the origin of Earth and its development through time 2. List at least three different geologic hazards. a. Volcanoes b. Tsunamis c. Landslides d. Floods e. Earthqueakes 3. Describe Aristotele’s influence on geology. a. He believed that rocks were created under the “influence” if the stars and hat earthqueakes occurred when air crowded into the ground, was heated by central fires, and escaped explosively. 4. Contrast catastrophism and Uniformitarism. How did each view the age of Earth? a. Catastrophism – believed that Earth’s landscapes were shaped primarly by great catastrophes. b. Uniformitarism – it states that the physical, chemical and biological laws that operate today have also operated in the geological past. 5. How old is Earth? a. About 4.6 billion years. 6. Why is an understanding of the magnitude of geologic time important for a geologist? a. Because many processes are so gradual that vast spans of time are needed before significant changes occur. 7. How is a scientific hypothesis different from a scientific theory? a. Theory – has proof and has been tested beforehand. 8. Summarize the basic steps followed in many scientific investigations/ a. Make a question b. Gather scientific data that relate to the question c. Questions that are related to the data are posed (create a hypothesis) d. The hypothesis is/are accepted, modified or rejected based on the testing e. Data and results are shared with the scientific community for critical examination and further testing. 9. What explains the fact that continental drift is considered a hypothesis but tectonic plates is considered a theory? a. Because the tectonic plates theory is backed up by the hypothesis of the continental drift, but the continental drift has no proof supporting the hypothesis.

10. List and describe Earth’s four spheres. a. Geosphere – The solid portion of the earth b. Biosphere – All living creatures c. Atmosphere – Gas sphere that allows us to breath d. Hydrosphere – All water in Earth 11. Compare the height of the atmosphere to the thickness of the geosphere. a. The atmosphere, eventhough is the largest of the spheres (having the biggest radio) its also the thinnest. The geosphere, eventhough being the smallest one (with the smaller ratio) is the biggest since it has the most “matter” of them all. 12. How much of Earth’s surface does oceans cover? What percentage of Earth’s total water supply do oceans represent? a. It covers 71% of Earth but if represents 97% of our water supply. 13. To which sphere does soil belong? a. To the geosphere. 14. What is a system? List three examples. a. A system is a group of interacting, or interdependent, parts that form a complex whole. i. Car’s cooling system ii. City transportation system iii. Weather system iv. Solar system v. Milky Way Galaxy 15. What are the two sources of energy for the Earth system? a. Sun’s energy b. Earth’s inner energy 16. Predict how a change in the hydrologic cycle, such as increased reainfall in an area, might influence the biosphere and geosphere in that area. a. To much rainfall can affect the geosphere by floods and landslides and the biosphere by “killing” or drowning plants, animals and humans. 17. Name and briefly outline the theory that describes the formation of our solar system. a. The Big Bang i. An incomprehensibly large explosion that sent all matter of the universe flying outward at incredible speeds. The debris from this explosion, which was almost entirely hydrogen and helium, began to cool and condense into the first stars and galaxies. It was in one of these galaxies, the Milky Way, that our solar system and planet Earth took form. 18. List the inner planets and the outer planets. a. Inner planets i. Mercury ii. Venus iii. Earth iv. Mars b. Outter planets i. Jupiter ii. Saturn iii. Uranus iv. Neptune

19. Explain why density and buoyancy were important in the development of Earth’s layered structure. a. Because the density of all the ocean is bigger in comparison with the continental plates, making it float and knowing it as we now know it nowadays. 20. List and describe the three major layers defined by their chemical composition. a. Crust – The outer skin of Earth b. Mantle – Solid and high heat c. Core – liquid, the highest heat and most pressure 21. Contrast the lithosphere and asthenosphere. a. Lithosphere – consist of the entire crust plus the uppermost mantle and forms Earth’s relatively cool, rigid outer shell b. Asthenosphere – a comparatively weak layer that is soft and liquid. 22. Distinguish between the outer core and the inner core. a. The outer core is a liquid layer that is 2270 kilometers thick b. The inner core is a sphere that has a 1216 kilometers radius. Despite its higher temperatures, the iron in the inner core is solid due to the immense pressures that exist in the center of the planet. 23. List two rock characteristics that are used to determine the processes that created a rock. a. Minerals b. Textures 24. Sketch and label the basic rock cycle. Make sure to include alternate paths. a. It melts b. It cools and crystallize c. It weathers d. Lithification e. Metamorphism 25. Use the rock cycle to explain the statement “One rock is the raw material for another”. a. The sedimentary rock comes from the igneous rock b. The metamorphic rock comes from the sedimentary rock c. The igneous rock comes from the metamorphic rock 26. Compare and contrast continents and ocean basins. a. The continents are remarkably flat and less dense than the ocean basins. 27. Describe the general distribution of Earth’s youngest mountains. a. The circum-Pacific belt (the region surrounding the Pacific Ocean) 28. What is the difference between shields and stable platforms? a. Shields are flat regions composed largely of deformed igneous and metamorphic rocks b. Stable platforms are other flat areas of the craton, in which highly deformed rocks, like those found in the shields, are covered by a relatively thin veneer of sedimentary rocks. 29. What are the three major regions of the ocean floor, and what are some features associated with each? a. Continental Margins – the portion of the seafloor adjacent to major landmasses. b. Deep ocean basins – are between the continental margins and oceanic ridges c. Ocean ridges...