Earth: An Introduction to Physical Geology PDF

Earth: An Introduction to Physical Geology Thirteenth Edition Chapter 1 Lecture An Introduction to Geology Copyright @ 2021...

Earth: An Introduction to Physical Geology Thirteenth Edition Chapter 1 Lecture An Introduction to Geology Copyright @ 2021 Regina Capuano Copyright © 2020, 2017, 2014 Pearson Education, Inc. All Rights Reserved The Science of Geology (1 of 4) Geology is the study of the Earth – Physical geology (this course) – study of earth materials and the processes that operate beneath and on the surface of our planet – Historical geology – study of the origin of Earth and its development through time 2 The primary difference between Physical and Historical Geology is that________. a. Historical Geology is about what people experienced on Earth in the past and Physical Geology is about the shape of Earth. b. Physical Geology is about modern time and Historical Geology is about the past. c. Physical Geology is about the processes that have shaped Earth over time and Historical Geology is about how we can reconstruct the record of change on Earth. d. Physical Geology is the study of rocks and Historical Geology is the study of fossils. The Science of Geology (1 of 4) Geologist study the earth It involves both outdoor fieldwork and laboratory work Geologists need a background in geology, chemistry, physics, mathematics, biology, and programing.  The Science of Geology (2 of 4) Geology has an influence on people and on the environment. Similarly, people have an influence on geology and the environment. As the world population increases the greater our influence on Natural hazards Global climate change Resources Now predicting a population decline The Science of Geology (3 of 4) Natural hazards are natural processes that become a hazard when they occur where people live. – volcanoes, floods, tsunamis, earthquakes, and landslides. – As the world population increases more people must live where they risk death and damage from significant geologic hazards. Earthquake in Ecuador The Science of Geology (4 of 4) Global climate change is naturally variable, however human activity (and increased population) influences this change Resources – Earth is a source of resources – water, soil, metallic and nonmetallic minerals, and energy – increased population stresses our limited supply of resources Open pit mine in southern Arizona The Development of Geology Before 1795, it was thought Earth’s landscapes were shaped primarily by catastrophes (Catastrophism) In 1795 – James Hutton (note you do not need to memorize this date or name) – Uniformitarianism- The physical, chemical, and biologic laws that operate today have operated throughout the geologic past The present is the key to the past – Used to prove Earth is very old (Earth is 4.6 billion years old) Earth processes vary in intensity but still take a very long time to create or destroy major landscape features. The magnitude of geologic time involves millions and billions of years. Slow Fast Monument Valley, AZ. Meteor Crater, AZ 9 bd  10 We have lots of examples of catastrophic natural events, like earthquakes, hurricanes, and landslides. So how do geoscientists explain these events when Uniformitarianism appears to describe only slow processes and this view replaces Catastrophism? a. Earthquakes, hurricanes, and landslides are not part of geology. b. Catastrophes happen but they do not obey the concept of Uniformitarianism, so scientists cannot predict them. c. Catastrophes happen and they are explained by Uniformitarianism, because the processes that cause them are known. d. Catastrophes do not really happen. The news reports tend to exaggerate some relatively minor events that scientists understand well. The Nature of Scientific Inquiry – don’t be fooled 11 The Nature of Scientific Inquiry How or why things happen are explained using the Scientific Method. Scientific Method – the process by which researchers raise questions, gather data, and formulate and test scientific hypotheses – Observations – are statements based on data. – Hypothesis – is an untested explanation of observations – Theory - a well-tested and widely accepted view that the scientific community agrees best explains certain observable facts. A well tested and accepted hypothesis becomes a theory. A Theory is NOT a law of nature, it could still at some time in the future be changed. Assumption (something accepted as true where no proof is given) should not be used in scientific inquiry. This is NOT the scientific method. Measurements show that climate is changing at an alarmingly fast rate, but the details of the mechanism for the change are still being worked out. Does this make global climate change a Theory, Hypothesis, Observation, Fact, or a completely disproven idea? a. Theory b. Hypothesis c. Assumption d. Observation e. Disproven Idea “alarming fast rate” is an observation, why it is happening would be a hypothesis. Earth as a System (1 of 5) Earth is a dynamic body with many separate, but interacting, parts (spheres): – Hydrosphere - global ocean and fresh water – Atmosphere - gaseous envelope – Geosphere - the solid Earth – Biosphere - all plant and animal life Earth as a System (2 of 5) Earth’s system is a group of interacting parts that form a complex whole. Earth system science: – Aims to study Earth as a system composed of numerous interacting parts – Employs an interdisciplinary approach to solve global environmental problems  Earth as a System (3 of 5) Interactions in Earth’s system can have a profound effect on plants and animals (including humans) – For example, in Southern California, drought results in deadly fires and loss of vegetation. – Later heavy rains on the slopes without vegetation, result in flashfloods and mudflows. A year after fires, deadly mudflows following heavy rain. Montecito, California,162018 Earth as a System (4 of 5) Cycles within the Earth System External processes – occur above Earth’s surface – The hydrologic cycle Internal processes – occur beneath Earth’s surface – The rock cycle 17 Earth as a System (5 of 5) Processes that occur in the Earth System are powered by Sun’s heat which drives the external processes of the hydrologic cycle. Internal heat of Earth from radioactive decay which drives the internal processes or the rock cycle 18  Origin and Early Evolution of Earth 4.6 Billion years ago material accumulated forming Earth which had no layers. After accumulating, Earth was hot enough that it melted, at which point density differences of the elements resulted in chemical differentiation. – More dense metals (iron and nickel) sank to the center forming the iron and nickel core. – Less dense elements (oxygen, silica and aluminum) rose to the surface as molten rock producing the crust. This created the three compositional layers of the Earth’s interior: core, mantle, and crust – At the same time, a primitive atmosphere evolved from volcanic gases 19 Earth has three compositional layers – Crust – a thin outer skin, divided into ▪ Oceanic crust crust ▪ approximately 7 kilometers thick ▪ Basaltic composition composed of the rock basalt. mantle ▪ Continental crust ▪ 35–70 kilometers thick core ▪ granitic composition composed primarily of the rock granodiorite – Mantle - approximately 2900 kilometers thick and composed of the rock peridotite – Core - composed of an iron-nickel alloy 20 Earth has five physical layers Earth is divided into layers based on physical properties (whether solid or liquid, rigid or soft). Lithosphere – solid and rigid – Consists of the crust and upper-most mantle Asthenosphere – solid but mobile, soft, and weak because very near its melting temperature. – Part of upper mantle Transition zone – solid, marked by a sharp increase in density. – Middle mantle Lower Mantle – solid, strong, very hot rocks subjected to gradual flow Outer core – – liquid (gives earth its magnetic field Inner core - solid  Continental Crust Oceanic Crust (Granitic composition) (Basaltic composition) Granodiorite Basalt Mantle Granite (ultramafic composition) Peridotite 22 Chemical differentiation, which led to the formation of chemical layers in the Earth, is based on what property of the materials involved? a. pressure b. temperature c. density d. viscosity Lithosphere versus continental and oceanic crust. Chemical Layers Physical Layers 24 Thickness of Earth’s crust (km) ▪ Oceanic crust approximately 7 kilometers thick ▪ Continental crust 35–70 kilometers thick 25 Sourcehttp://quake.wr.usgs.gov/research/structure/CrustalStructure/abstract.html  Rocks Rocks are composed of minerals Minerals are a chemical compound or an element, each with its own composition and physical properties. A rock’s mineral composition and texture give information the geologic processes that created it. – Texture is the size, shape or arrangement of minerals Mineral grains or crystals can be large or microscopic Coursed grained texture Fine grained texture Glassy texture Granite Basalt 26 Rocks and the Rock Cycle Rocks are divided into three major groups: The Rock Cycle – igneous, sedimentary, and metamorphic Igneous rocks – Form from cooling and solidification of molten rock Sedimentary rocks - Form from sediments undergoing lithification (which means “conversion into rock”) usually by compaction and/or cementation – The sediments are derived from weathering of preexisting rocks – Form on Earth’s surface Metamorphic rocks - Form by transforming (without melting) preexisting igneous, sedimentary, or other metamorphic rocks – Driving forces are heat and pressure The Face of Earth Earth is covered with either – continents (continental crust) 40% – ocean basins (oceanic crust) 60% 28 The Face of Earth - Continents Cratons - the stable interiors of continent that have been undisturbed for the last 100 million years – Shield – expansive flat area of old (weathered down) deformed crystalline rocks that are the exposed portion of the craton. – Stable platforms – portion of the craton covered with a thin layer of young sediments weathered off the shield. Mountain Belts – occur on the edges of some cratons. 29  The Face of Earth – Ocean Floor Continental margins – seafloor that is adjacent to major landmasses. – Tectonically inactive continental margins Continental shelf – portion of the continental crust that extend from the coastline Continental slope - steep drop-off that marks the true edge of the continent (note the edge is not at the coastline). Granitic Basalt The Face of Earth – Ocean Floor (2 of 3) Continental margins (cont.) – – Tectonically active continental margins Deep Ocean Trenches – deep, narrow depressions at subduction zones 31  Review Compare the two types of continental margins on the ocean floor. tectonically inactive tectonically active continental slope subduction zone 32 The Face of Earth – Ocean Floor (3 of 3) Abyssal plain - flat featureless expanse in the deep ocean. – Seamounts - volcanic structures that dot the ocean floor. Oceanic ridges (mid-ocean ridges) are the most prominent feature on the ocean floor and are composed of igneous rock that has been fractured and uplifted. The Face of Earth (3 of 6) Abyssal plain - flat featureless expanse in the deep ocean. Seamounts - volcanic structures that dot the ocean floor. Oceanic ridges (mid-ocean ridges) are the most prominent feature on the ocean floor and are composed of igneous rock that has been fractured and uplifted. Chapter 1 figure from GEODE Earth A B C D Oceanic Crust Continental crust Lithosphere Asthenosphere 35  Key Words Geology Asthenosphere Stable Interior Physical geology Transition Zone Craton Historical geology Lower Mantle Shield Earth system Inner core Stable Platform Hydrologic cycle Outer core Continental Margin Rock cycle Oxygen = O Continental Shelf Catastrophism Silica = Si Continental Slope Uniformitarianism Aluminum = Al Deep ocean basin Hypothesis Iron = Fe Ocean (mid-ocean) ridge Theory Magnesium = Mg Deep-ocean trench Scientific Method Sodium = Na Abyssal plain Chemical layers Potassium = K Volcanic arc Density Granite Sediment Crust Granodiorite Sedimentary rock Mantle Basalt Metamorphic rock Core Peridotite Igneous rock Fe-Ni Alloy Continental Crust Magma Physical layers Oceanic Crust Lithosphere Mountain belts 36  The End Some portions of this course contain material used under the Fair Use Exemption of US copyright law. 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