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Lab Exercise 6 - Geologic Maps and Principles

Purpose: This lab is to examine the order of events in geologic history of an area through interpretation of geologic maps. The goal is to understand geologic maps as they relate to gem and mineral resources in a region.
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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.
Shaded relief map of the United States
Physiographic provinces of the United States
Physiographic province of the United States
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.

Shaded Relief Map of the United States Physiographic Provinces Tapestry of Time and Terrain (USGS website) compares landscapes with underlying geology with physiographic provinces of the United States. Physiographic Provinces Map (blank)
Shaded Relief Map of the United States Physiographic Provinces on a geologic map   Blank physiographic Provinces Map

Defining a location on the Earth's surface using latitude and longitude coordinate system

—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.

—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°

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.
Global projection Mercator Map
Longitude and Latitude projected on a globe Map of the world showing latitude and longitude in a Mercator (flat) projection
California 7.5 minute quadrangle index Chittenden 7.5 minute quadrangle
Portion of the California Topographic Map Index Chittenden 7.5 minute quadrangle map
Topographic Map scale 1:24,000 Devils Tower Quadrangle
Scale on a 1:24,000 topographic map Part of Devils Tower Quadrangle, Wyoming
Gavilan Topographic Quadrangle Gavilan Colege Quadrangle 2012
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. 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.

San Juan Bautista 15 minute topographic map Geology on topography Geologic map
Topographic Map
San Juan Bautista
15 minute quadrangle
Topographic map with geology mapping Geologic Map
San Juan Bautista
15 minute quadrangle

Austin Texas DEM Mount St. Helens DEM shaded relief Devils Tower satellite image
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.
Grand Canyon photo Grand Canyon geologic map
Geologic Map Legend

Grand Canyon Grand Canyon Geologic Map
Grand Canyon cross section Grand Canyon cross section

Block Diagram of the Grand Canyon Geologic Cross Section of the Grand Canyon Geologic map legend for the Grand Canyon
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