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Chapter 1 - Introduction to Geology |
This Introduction to Geology class is an introduction to basic understanding of the physical environment of planet Earth, including Earth's place in space and time within the Universe, the materials that found on our planet, and the processes that change the the landscape around us. The focus of discussions range from looking at the Earth from a global perspective to features in our home in our local region of central California. The class and lab activities will be examing geological processes through geologic time.
The materials presented on this website are an expanded outline for topics discussed in class (and used for class quizzes, exams, and activities are presented in outline form. Students are encouraged to explore beyond the materials presented herein by searching topics of interest on the Internet or books found in the QE and QH section of the Library collections. |
1. Define geology, physical geology and historical geology.
2. Define science, observation, hypothesis, fact, theory, scientific law, and scientific methods.
3. Name the people and ideas involved with the early development of geology.
4. Describe the structure and general processes occurring in the Earth.
5. Described the basic ideas of geologic time and the origin of the Earth.
6. Describe and illustrate the "rock cycle" as it relates to processes and products observed on Earth and other planets.
7. Origin of the Earth within the Universe.
8. Define geomorphology and and the concept of physiographic provinces.
9. Explain the uses of maps and geologic illustrations in understanding geology.
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| Keywords and Essential Concepts |
1. Define geology, physical geology and historical geology.
geology—the study of the Earth.The scientific study of the origin, history, and structure of the earth. The structure of a specific region of the earth's crust. And, the scientific study of the origin, history, and structure of the solid matter of a celestial body.
physical geology—that branch of geology concerned with understanding the composition of the earth and the physical changes occurring in it, based on the study of rocks, minerals, and sediments, their structures and formations, and their processes of origin and alteration.
historical geology—the study of the composition, relative positions, etc., of rock strata in order to determine their geological history. Historical geology is dependent on concepts and order of events related to deep time, as defined by a geologic time scale.
What do geologists do?
* Geologists study earth processes: floods, earthquakes, landslides, volcanic eruptions
* Geologists explore and manage resources: oil & gas, water, metals, rock byproducts
* Geologists work in environmental fields: climate change, waste management
* Geologists work in construction and engineering: archeology, foundations, marine
* Geologists serve in national security and epidemiology
* Geologists work in education: schools, parks, museums |
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2. Define science, observation, hypothesis, fact, theory, scientific law, and scientific methods.
science—she systematic knowledge of the physical or material world gained through observation and experimentation. The overall goal of science is to discover underlying patterns in the natural world. The fundamental assumption of science—"the natural world behaves in a consistent and predictable manner."
scientific method—the principles and empirical processes of discovery and demonstration considered characteristic of or necessary for scientific investigation, generally involving the observation of phenomena, the formulation of a hypothesis concerning the phenomena, experimentation to demonstrate the truth or falseness of the hypothesis, and a conclusion that validates or modifies the hypothesis.
observation—the act of noting and recording something, such as a phenomenon, with instruments, in order to gain information.
hypothesis—a tentative explanation for an observation, phenomenon, or scientific problem that can be tested by further investigation.
fact—Knowledge or information based on real occurrences; something demonstrated to exist or known to have existed.
theory—A set of statements or principles devised to explain a group of facts or phenomena, especially one that has been repeatedly tested or is widely accepted and can be used to make predictions about natural phenomena. (A theory is also defined as an assumption based on limited information or knowledge.)
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3. Name the people and ideas involved with the early development of geology.
Early contributions to geology
Nicolas Steno (1638-1686)—Promoted science of the origin of fossils, basic stratigraphy principles.
fossil—A remnant or trace of an organism of a past geologic age, such as a skeleton or leaf imprint, embedded and preserved in the earth's crust.
stratigraphy—A branch of geology concerned with the systematic study of bedded rocks and their relations in time and the study of fossils and their locations in a sequence of bedded rocks.
stratum— a bed or layer of sedimentary rock having approximately the same composition throughout (plural is strata).
James Hutton (1726-1797)—promoted "uniformitarianism", modern concepts of Geologic Time, theory of "rock formations"
rock formation—the primary unit of stratigraphy, consisting of a succession of strata useful for mapping or description. A rock formation typical consists of a unique lithology (rock type) that has a relatively defined geologic age and is considered "mapable" (occurs throughout area or region, both on the surface and in the subsurface.
uniformitarianism—the theory that all geologic phenomena may be explained as the result of existing forces having operated uniformly from the origin of the earth to the present time.
catastrophism—the doctrine that major changes in the earth's crust result from catastrophes rather than evolutionary processes.
William Smith (1769–1839)—Prepared the "map that changed the world" - first geologic map of the British Isles.
Charles Lyell (1797-1875) —Wrote "Principles of Geology" (first geology text), promoted concepts of the "rock cycle"
Charles Darwin (1809-1882) —Wrote "Origin of Species" (1858) - Developed early concepts of the theory of evolution of life.
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4. Describe the structure and general processes occurring in the Earth.
| structure of the earth—The earth's lithosphere has a central core (solid & liquid), the mantle (including asthenosphere), and the crust. |
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| Structure of the Earth |
atmosphere—the gaseous mass or envelope surrounding a celestial body (including the one surrounding the Earth), and retained by the celestial body's gravitational field. The Earth's atmosphere is subdivided into levels: the troposphere is the lowest portion (up to about 6-8 miles) where all weather takes place and contains about 80% of the air's mass and 99% of water vapor. The overlying stratosphere contains an abundance of ozone which absorbs ultraviolet radiation, protecting life on land and in the shallow ocean extends up to about 31 miles. The upper atmosphere extends upward to the transition into space above about 60 miles where the charged atomic particles of the solar wind begins to interact with atmospheric gases.
hydrosphere—all the waters on the Earth's surface, such as oceans, lakes, rivers, and streams.
lithosphere—the rocky outer portion of the Earth, consist of the crust and upper mantle (about the upper 60 miles below the Earth's surface).
biosphere—the regions of the surface and atmosphere of the Earth (or possibly other planets) occupied by living organisms.
crust— the outermost solid shell of a rocky planet or moon, which is chemically distinct from the underlying mantle.
mantle—an inner layer of a terrestrial planet or other rocky body large enough to have differentiated in composition by density. On Earth, the mantle is a highly viscous layer between the crust and the outer core.
core—based on geophysical studies, the innermost part of the earth is believed to consist of a 758 mile thick magnetic metallic core overlain by a 1400 mile thick zone of molten material. This is overlain by the Earth's mantle. |
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5. Described the basic ideas of geologic time and the origin of the Earth.
geological time—the time of the physical formation and development of the earth (especially prior to human history). Geologic time also applies to the age and history of the Universe.
geologic time scale—Geologists have subdivided periods in Earth's history is measured periods spanning millions of years (Ma). Segments of time periods have been named to help define the chronology of events (such as mountain range formation), the formation of rock units (such as the age of a lava flow), the age of fossils, organizing geologic map units, and other purposes. Below is a standard geologic time scale listing names of major time periods with time span information. |
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| Geologic Time Scale |
"If a second were 100,000 years" |
relative dating—the science determining the relative order of past events, without necessarily determining their absolute age.
absolute dating—general term applied to a range of techniques that provide estimates of the age of objects, materials, or sites in real calendar years either directly or through a process of calibration with material of known age.
Absolute dating methods include the study of the decay radioactive isotopes (such as C14, and uranium to lead, and potassium to argon). |
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| Relative dating exercise |
Absolute dating methods |
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6. Describe and illustrate the "rock cycle" as it relates to processes and products observed on Earth and other planets.
| rock cycle—the series of events in which a rock of one type is converted to one or more other types and then back to the original type. The "rock cycle" is a graphic and conceptual model to illustrate common rocks and earth materials and the processes that form or change them. |
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These rock cycle diagrams illustrate how earth materials form and change over time. Both products (rocks and sediments) and processes (such as melting, cooling, erosion, and deposition) are illustrated. The passage of geologic time is an essential component, although some processes are much faster than others. Note that all these types of processes are taking place simultaneously, but at different locations on and within the planet. |
| The Rock Cycle |
Rock Cycle Illustrated |
igneous rocks—A rock formed from molten materials, includes intrusive rocks (rocks cooled below the surface) and rocks formed on the Earth's surface by volcanism (and from melting associated with extraterrestrial impacts).
sediments—solid fragments of inorganic or organic material that come from the weathering of rock and soil erosion, and are carried and deposited by wind, water, or ice.
sedimentary rock—rock that has formed through the deposition and solidification of sediment, especially sediment transported by water (rivers, lakes, and oceans), ice ( glaciers), and wind. Sedimentary rocks are often deposited in layers, and frequently contain fossils.
metamorphic rocks—Rock that was once one form of rock but has changed to another under the influence of heat, pressure, or fluids without passing through a liquid phase (melting). |
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7. Origin of the Earth within the Universe.
Origin of the Earth in the Universe
big bang theory—a cosmological theory holding that the observable universe originated approximately 20 billion years ago from the violent explosion of a very small agglomeration of material of extremely high density and temperature. See a NASA website about the Big Bang Theory.
galaxy—a system of millions to billions of stars, together with gas and dust, held together by gravitational attraction. Earth is in the Milky Way galaxy. See a NASA website about Galaxies.
star—a self-luminous celestial body consisting of a mass of gas held together by its own gravity in which the energy generated by nuclear reactions in the interior is balanced by the outflow of energy to the surface, and the inward-directed gravitational forces are balanced by the outward-directed gas and radiation pressures. Our sun is our star in the center of our solar system. See a NASA website about Life Cycle of Stars.
nebula—an interstellar cloud within a galaxy consisting of gas and dust, typically glowing from radiant energy from stars nearby within them. Nebulas are the birth place of stars and solar systems, and can form from the explosion of stars at the end of their life cycle.
solar system—the system containing the sun and the bodies held in its gravitational field, including the planets (Mercury, Venus, Earth, Mars, Jupiter, Saturn, Uranus, Neptune, Pluto), planetary moon, the asteroids, and comets, and other interstellar matter. See NASA websites about Planets and Moons within the Solar System and Earth's Moon.
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| Spiral galaxy: a typical galaxy may have hundreds of millions of stars |
Distant field of galaxies: galaxies can be seen in all directions in distant space |
Sun (our star) |
Nebula, the birthplace of stars; some are formed from the explosion of others |
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| Mercury |
Venus |
Earth |
Mars |
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| Jupiter |
Saturn |
Uranus |
Neptune |
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| Pluto |
Earth's Moon |
Asteroids |
Comet |
asteroid—any of the thousands of small irregularly shaped bodies of stone, metal, and ice that revolve about the sun. In our solar system, asteroids typically range in size from about one-mile (1.6 km) to about 480 miles (775 km) in diameter. Most asteroids lie in in orbits between those of Mars and Jupiter, however many large objects have been observed passing through Earth's orbital path. Asteroid collisions with earth were frequent in Earth's early history, but are now extremely rare events. The extinction of the dinosaurs and many other species is mostly blamed on the environmental catastrophe created by an asteroid impact about 65 million years ago, defining the end of the Cretaceous Period (and Mesozoic Era). See a NASA website about asteroids.
comet—a celestial body, observed only in that part of its orbit that is relatively close to the sun, having a head consisting of a solid nucleus surrounded by a nebulous coma up to 2.4 million kilometers (1.5 million miles) in diameter and an elongated curved vapor tail arising from the coma when sufficiently close to the sun. Comets are thought to consist chiefly of ammonia, methane, carbon dioxide, and water. See a NASA website about comets.
meteor—a bright trail or streak that appears in the sky when a meteoroid is heated to incandescence by friction with the earth's atmosphere.
meteorite—a stony or metallic mass of matter that has fallen to the earth's surface from outer space. See a NASA website about
meteors and meteorites.
bollide—a large meteor (or asteroid or comet) that explodes in the atmosphere. See a NASA website about bollides. |
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8. Define geomorphology and and the concept of physiographic provinces.
The links between the traditional studies of Geography and Geology intersect in the science of Geomorphology.
geomorphology—the study of the earth's surface including classification, description, nature, origin, and development of landforms and their relationships to underlying structures and the history of geologic changes as recorded by these surface features.
Primary studies of landscapes involve generating map of many kinds, including natural landscape features (such as rivers, mountains, shorelines), man-made features (cities, roads, dams, etc.), ecology and land use (natural and agricultural) and much more. Regions of the North American landscape have been subdivided in to areas sharing similar physical characteristics, such as topography (relief), geologic history, ecology, and climate. These subdivisions on a map are called Physiographic Provinces.
physiographic province—a geographic region with a specific geomorphology and often specific subsurface rock type, age, or structural elements. See more information on the Physiographic Provinces of the United States web page. |
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| Physiographic provinces |
topography—the arrangement of the natural and artificial physical features of an area. A topographic map is a graphical representation of a landscape showing selected natural and artificial landscape feature including topographic relief.
relief—the variation in elevation on the surface of the Earth (topography). Areas of high relief have much elevation changes over distance, such as mountainous areas and canyons. Low relief occurs where elevation changes are minimal, such as on coastal plains. |
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9. Explain the uses of maps and geologic illustrations in understanding geology.
| map—a diagrammatic representation of the earth's surface or part of it, showing the geographical distributions, positions, etc., of natural or artificial features such as roads, towns, relief, rainfall, etc. Essential components of a usable map include a title, a scale (such a 1 inch = 2000 feet), a legend defining symbols on the map, geographic orientation (north arrow and corner coordinates), and source (names, place, and date of origin). |
Defining a location on the Earth's surface using latitude and longitude coordinate system
latitude—The angular distance of a place north or south of the earth's equator, usually expressed in degrees and minutes. Lines of latitude are called parallels. Latitude lines parallel the Equator. Each degree of latitude is approximately 69 miles (111 kilometers) apart.
longitude—the angular distance of a place east or west of the Prime Meridian (established at Greenwich, England in 1884), usually expressed in degrees and minutes. Longitude lines are widely spaced at the equator but converge at point at the North and South Poles. The Prime Meridian is designated 0° (zero degrees). Meridian lines east of the Prime Meridian are designated positive values (0° to 180° east); whereas meridian lines west of the Prime Meridian are designated negative values (-0° to -180°). At 180° east or west is the International Date Line. A degree of longitude is widest at the equator at 69.172 miles (111.321) and gradually shrinks to zero at the poles. At 40° north or south the distance between a degree of longitude is 53 miles (85 km).
Defining locations with a latitude-longitude coordinate system—any location on the planet surface can be defined by a number in degrees, minutes, and seconds north or south of the Equator and east or west of the Prime Meridian.
Example: Location of the Statue of Liberty in New York Harbor
The standard coordinates of the are:
Latitude: 40°68′92"N
Longitude: 74°04′ 45"W.
Described in decimal degrees the coordinates of the Statue of Liberty are: Latitude:40.689758°
Longitude:-74.045138° |
| Find the latitude and longitude of any named location or landscape feature on the GeoNames website. |
Global Positioning System (GPS)—a space-based global navigation satellite system that provides reliable location and time information in all weather and at all times and anywhere on or near the Earth when and where there is an unobstructed line of sight to four or more GPS satellites.
quadrangle—a standardized area used in mapping to designated an area on the Earth's surface. In the United States, the area shown on one of the standard 7.5 minute quadrangle map sheets (published by the U.S. Geological Survey): approximately 17 miles (27 km) north to south and from 11 to 15 miles (17 to 24 km) east to west. In a 1° by 1° quadrangle area, there are sixty-four 7.5 minute quadrangles.
topographic map—map showing relief and man-made features of a portion of a land surface distinguished by portrayal of position, relation, size, shape, and elevation of the features. Topographic maps have contours, which are lines that represent the location of equal elevations, typically measured in feet or meters above standard mean sea level. See a website describing Topographic Map Symbols.
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| Longitude and Latitude projected on a globe |
Map of the world showing latitude and longitude in a Mercator (flat) projection |
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| Portion of the California Topographic Map Index |
Chittenden 7.5 minute quadrangle map |
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| Scale on a 1:24,000 topographic map |
Part of Devils Tower Quadrangle, Wyoming |
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| Portion of the Chittenden Quadrangle topographic map |
Portion of the Chittenden Quadrangle topographic map (2012 version) |
Standard Maps and Digital Map Data
Types of Maps (American Geological Institute)
USGS National Map Viewer (free online access to topographic maps and other data)
See the USGS Maps, Imagery, and Publications (a website to download free digital maps and imagery)
Learn about all kinds of maps for California (Humboldt State University Library website)
See Historic USGS topographic quadrangle maps of the Monterey Bay region (UC Berkeley)
digital elevation model (DEM)—A digital elevation model (DEM) is a digital representation of ground surface topography or terrain. It is also widely known as a digital terrain model (DTM). A DEM can be represented as a raster (a grid of squares) or as a triangular irregular network. A DEM is used for the generation of contours, shaded relief, 3-D terrain models and elevation profiles.
shaded relief map—A map of an area whose relief is made to appear three-dimensions using gray-scale shading based on a hypothetical sun angle, typical of late afternoon (north and east facing slopes appear darker than south and west facing slopes).
satellite image map—a map generated from raw satellite imagery data that has been rectified to match a grid associated with a standardize map grid, such as a USGS 7.5 minute quadrangle, a "digital orthoquad", or DOQ. Google.com provides satellite image maps along with standardized road maps on their maps search website.
geologic map—a special-purpose map made to show geological features. Types and ages of rock units are shown by color or symbols to indicate where they are exposed at or near the surface. A geologic map records the distribution, nature, and age relationships of rock units and the occurrence of structural features (such as the location of faults). They depict the land as if all soil and vegetation were stripped away. Geologic maps are used by paleontologists to find areas that are likely to contain fossils, and by geologists and engineers to define the location of faults, economic mineral resources, to find potential underground water resources, and more. |
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Tapestry of Time and Terrain (USGS website) compares landscapes with underlying geology with physiographic provinces of the United States. |
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| Shaded Relief Map of the United States |
Physiographic Provinces on a geologic map |
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Blank physiographic Provinces Map |
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Topographic Map
San Juan Bautista
15 minute quadrangle |
Topographic map with geology mapping |
Geologic Map
San Juan Bautista
15 minute quadrangle |
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| Example of raw DEM data: Digital elevation model of downtown Austin, Texas |
Shaded relief model made with DEM data for Mount St. Helens, Oregon |
Satellite imagery data (digital othoquad (DOQ)
Devils Tower, Wyoming |
Interpreting the Earth structure with maps and illustrations
Geologic Maps, Cross Sections, Block Diagrams used to show the structure of the Earth in 3 dimensions.
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| Grand Canyon |
Grand Canyon Geologic Map |
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| Block Diagram of the Grand Canyon |
Geologic Cross Section of the Grand Canyon |
Geologic map legend for the Grand Canyon |
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