One of the key features to measure is the orientation, or attitude, of bedding. In addition to a topographic map, a complete understanding of the underlying geologic structure and history of an area requires completion of a geologic map and cross-sections. Instead, the edge of a piece of paper is laid along the line of profile and the contour line data is transferred to the edge of the piece of paper. The hinge of the fold is denoted with a dashed line with two arrows point away from it. Geologic maps are also vital in finding and developing geological resources, such as gravel to help build the road you drive on, oil to power the car you travel in, or aluminum to build the more fuel-efficient engine in your next vehicle. Beneath the fractional scale, the map scale is also depicted a different way, in bar scales using three different units. They can also find clues to the underlying geologic structure and geologic history of the area. The walls are stepped. Ask for players’ emails to identify them. Key Topics. http://www.ck12.org/book/CK-12-Earth-Science-Concepts-For-High-School/section/2.5/, https://commons.wvc.edu/rdawes/G101OCL/Basics/mapkey.html, https://commons.wikimedia.org/wiki/File:LoihiBathemetric.jpg, strike and dip of beds other than horizontal or vertical, low-angle normal fault, footwall—gneiss, hanging wall—shallow-crust rocks, high-angle (45° or more dip) thrust fault, rocks on either side move horizontally in opposite directions. In case you additional materials for your assignment, you will be directed to ‘manage my orders’ section where you can upload them. Reading a topographic map requires familiarity with how it portrays the three-dimensional shape of the land, so that in looking at a topographic map you can visualize the shape of the land. It tells you, among other things: One of the important tools you can use to extract the vertical information from a topographic map, and see more clearly the shape of the earth’s surface that it represents is a topographic profile. Arun Kumar. Many geologists have experience mapping some part of the earth’s surface. Bathymetric maps are like topographic maps of features found below the water. Did you have an idea for improving this content? This view of the surface shows patterns that provide information about the geology beneath the surface. Read the text again and answer these questions. (You might note that this map does something unusual for a topographic map. Maps are essential tools in geology. You may stop watching at the 4:04 mark. Elevations indicate height above sea level. This means that 1 inch on the map corresponds to 24,000 inches in the real world represented by the map, or 1 cm equals 24,000 cm; in other words, distances on the map have been shrunk by a factor of 24,000 from their real-world size. They are important accompaniments to geologic maps, especially if the map focuses on the geology of the bedrock underneath the soil and loose sediments. Geologists are trained in map reading and map making. The geology is superimposed on a topographic map to give a more complete view of the geology of the region. Click on the image to view a larger version. Geologists take great pains to measure and record geological structures because they are critically important to understanding the geological history of a region. Topographic profiles are usually constructed without drawing any lines on the map. As a result, the topographic profile is greatly exaggerated vertically. Poor infrastructure 2. Ensure you request for assistant if you can’t find the section. The symbol for each rock or sediment unit is shown in a box next to its name and brief description. The symbol for arc seconds is a double apostrophe or quotation mark: “. Q65: India is an important iron and steel producing country in the world yet, we are not able to perform to our full potential largely due to: 1. The topographic maps drawn and published by the U. S. Geological Survey portray the grids that are used on deeds to identify the location of real estate, so homeowners and property owners sometimes find it useful to refer to topographic maps of their area. To draw the profile, the grid must be crossed by evenly-spaced horizontal lines that represent the contour elevations. Download Full PDF Package. Then answer the questions. if the strike is 0˚ (i.e., north) and the dip is 30˚, it would be necessary to say “to the west” or “to the east.”  Similarly if the strike is 45˚ (i.e., northeast) and the dip is 60˚, it would be necessary to say “to the northwest” or “to the southeast.”. In this context, they are usually just called minutes and seconds, but it must be kept in mind that these minutes and seconds are units of angles, not units of time. (a) Igneous rocks (b) Metamorphic rocks (c) Igneous and metamorphic rocks (d) Igneous, metamorphic & sedimentary rocks. the map legend or key that explains all the symbols on the map. A topographic profile with a VE of 120 would be a very exaggerated topographic profile. The dyke is dipping at 80˚ to the west. (Vertical grid lines are not required.). This is consistent with the elevations of those parts of the line of profile on the map. In this example, the map covers 0.25 miles horizontally in less distance than the profile covers 100 feet vertically. Where contours are close together, the topography is steep; where contour lines are far apart, the slope is gentle or flat. A topographic map provides the frame of reference upon which most geologic maps are constructed. If included, cross-sections are usually printed on the same page as the geologic map. ), Contour lines on standard US Geological Survey topographic maps are brown — e. The elevation of a point on the map that is not on a contour line must be estimated as greather than the elevation of the nearest contour line below it, and less than elevation of the nearest contour line above it. We know that sedimentary beds are deposited in horizontal layers, so if the layers are no longer horizontal, then we can infer that they have been affected by tectonic forces and have become either tilted, or folded. The ends and any high points or low points of the topographic profile should be above or below elevation lines, not on them, except in cases where an end, high point, or low point of a line of profile happens to fall right on a contour line. READ PAPER. The strike is the compass orientation of the wall and the dip is 90˚ from horizontal. What are the relative ages of the nine geological features shown here (seven beds, dyke, and fault)? The width of the grid should be the same as the length of the line of profile. The beds on the east side are dipping to the east. A complete geologic map has at least two features: Professional geologic maps usually have two other components as well: The legend or key to a geologic map is usually printed on the same page as the map and follows a customary format. The inclined section of the wall is known as the batter, and the flat part of … A geologic map of the region around Old Faithful, Yellowstone National Park. By stacking the units in age sequence from youngest at the top to oldest at the bottom, and identifying which interval of geologic time each unit belongs to, the map reader can quickly see the age of each rock or sediment unit. 1. Weathering wears down these otherwise solid structures, making it much easier for other processes to change a landform. Rock units are color-coded and identified in a key. In symbols, 60′ = 1° means there are 60 minutes in 1 degree. The landforms of the earth result from surface processes such as erosion or sedimentation combined with internal geological processes such as magma rising to create a volcano or a ridge of bedrock pushed up along a fault. The vertical exaggeration of a topographic profile can be calculated. The name of the quadrangle comes from the name of a place on the map. In 1962, the magnetic North Pole, as measured from the Juniper quadrangle, was located 20.5° east of true north. However, you will be expected to develop your map reading skills as you use maps to help you learn geology. In symbols, 60″ = 1′ means there are 60 seconds in 1 minute. This accords with the rules of contour lines, which state that slopes are steeper where contour lines are more closely spaced, and slopes are less steep where contour lines are more widely spaced. To convert arc minutes into a decimal fraction of a degree, multiply the number of arc minutes by 1°/60′. The elevation of each contour line corresponds to the vertical coordinate of each corresponding point on the profile grid, as shown on the diagram below. One of the key features to measure is the orientation, or attitude, of bedding. Another resource that is developed on the basis of geologic maps is groundwater, which many cities, farms, and factories rely on for the water they use. Loihi volcano growing on the flank of Kilauea volcano in Hawaii. The map scale. Rock units are color-coded and identified in a key. A geologic map shows the geological features of a region (see figure 4 for an example). A map quadrangle spans a fraction of a degree of longitude east-to-west and the same fraction of a degree of latitude north-to-south. Geologic maps show rock units and geologic features like faults and folds. There is also a reminder that elevations shown on the map are elevations above mean (average) sea level on earth. Because lines of longitude degrees (also called meridians) in the Northern Hemisphere come closer and closer together the nearer they get to the North Pole, whereas lines of latitude degrees remain the same distance apart as they circle the earth, quadrangle maps span less distance east-to-west than they do north-to-south. The image above is from the bottom of the Juniper 7.5 minute quadrangle. To the left of the bar scales, the magnetic declination is shown as an arrow diverging from a line oriented toward true north. Irregular supply of energy 4. The answer is relatively simple. (The short lines sticking out of the contour lines are called hachures, hatch marks, or tick marks. Longitude is how far east or west, up to a maximum of 180°, a point on earth is from the Prime Meridian. A bathymetric map is like a topographic map with the contour lines representing depth below sea level, rather than height above. The map key also contains a listing and explanation of the symbols shown on the map, such as the symbols for different types of faults and folds. Key of G (1 sharp) Key of D (2 sharps) Key of A (3 sharps) Key of E (4 sharps) Key of B (5 sharps) Key of F Sharp (6 sharps) Key of C Sharp (7 sharps) Tricks to Remember Key Signatures Flats. If you were to walk along a contour line, what would happen to your elevation? The magnetic North Pole wanders a few miles every year and the magnetic declination of 20.5° east of true north was determined in the year 1962; it may be slightly different now. Here’s a reminder of how metamorphic rocks are formed and what they look like. Because the meridians converge at the poles, a degree of longitude gets smaller and smaller near each pole. Depending on which part of the map you want to see in profile, you can draw your line of profile in any direction you choose, across any part of the map you choose. Contour lines do not intersect each other, because a point on the surface of the earth cannot be at two different elevations. If it were a syncline, the arrows would point towards the line. Construction of a topographic profile allows you to visualize the vertical component of a landscape. Elevations indicate depth below sea level. Strike and dip are also used to describe any other planar features, including joints, faults, dykes, sills, and even the foliation planes in metamorphic rocks. Most topographic maps make use of contour lines to depict elevations above sea level. The completed topographic profile and the map it was drawn from are shown below. A mappable unit of rock or sediment is one that a geologist can consistently recognize, trace across a landscape, and describe so that other people are able to recognize it and verify its presence and identity. This depends on how weathered the rocks are, and the type of rock, and also how many structural weaknesses occur within the rocks, such as a faults, shears, joints orfoliations. If you pushed the wall over completely so it was lying on the floor, it would no longer have a strike direction and its dip would be 0˚. Elevation lines are labeled along the left-hand vertical axis. The Prime Meridian, 0° longitude, is a north-south line that runs through Greenwhich, England. Given a topographic map such as the one below, here’s how to construct a topographic profile. Determine the line of profile, the line across that part of the map that you want to see in profile or cross-section view. In simpler terms, just divide the number of arc minutes by 60 to convert to decimal degrees. A properly drawn topographic profile will have the following attributes: Use this resource to answer the questions that follow. We can express the orientation of a bed (or any other planar feature) with two values: first, the compass orientation of a horizontal line on the surface—the strike—and second, the angle at which the surface dips from the horizontal, (perpendicular to the strike)—the dip (Figure 12.18). Find the following information using this corner of the map: Important information is shown at the bottom of a USGS quadrangle map, including the map scale, the contour interval, and the magnetic declination. There are 60 arc seconds in 1 arc minute. HowStuffWorks explains thousands of topics, from engines to lock-picking to ESP, with video and illustrations so you can learn how everything works. One of the bar scales is in miles, one is in units of thousands of feet, and one is in kilometers. Creative Commons Attribution 4.0 International License. Faults and folds are also shown on geologic maps. Place strike and dip symbols on the map to indicate the orientations of the beds shown, the fault, and the dyke. Meridians, lines of longitude, run from the South Pole to the North Pole, converging (coming together) at the poles. Transfer the contour elevations from the topographic map to the profile grid. Kilauea is the youngest volcano found above sea level in Hawaii. Similarly, the ends of the profile are below 400 ft but above 380. By studying the shape of the earth’s surface through topographic maps, geologists can understand the nature of surface processes in a given area, including zones subjected to landsliding, places undergoing erosion and places where sediment is accumulating. Measurement of geological features is done with a special compass that has a built-in clinometer, which is a device for measuring vertical angles. The explanations of rock units are often given in a separate pamphlet that accompanies the map. The Complete Guide to the TOEFL ® Test iBT EDITION AUDIO SCRIPTS AND ANSWER KEY. The topographic profile is drawn on a rectilinear graph with evenly spaced grid lines. If the vertical scale on the profile is different from the map scale, the resulting amount of vertical exaggeration is listed. [SE]. Geologic cross-sections are constructed on the basis of the geology mapped at the surface combined with an understanding of rocks in terms of physical behavior and three-dimensional structures. Figure 3. To divide by a fraction, you can invert and multiply, so this becomes [latex]\displaystyle\left(\frac{1}{200}\right)\times\left(\frac{24,000}{1}\right)=\frac{24,000}{200}=120[/latex]. You are not expected to become a geological expert in reading maps. It is the fractional scale of the topographic profile’s vertical axis, divided by the fractional scale of the map. Notice on the topographic profile constructed above that the peak of the hill is above 520 ft, but below 540 ft. See the Table of Geologic Map Symbols for pictures and an overview of the map symbols, including strikes and dips, faults, folds, and an overview. The geologic era, or period, or epoch–the geologic age–is listed for each rock unit in the key. an accompanying explanation of the rock or sediment units, strike (longer line) is horizontal line on bedding plane, strike parallels nearby contacts between stratified rocks, dip angle, number at end of dip symbol, is how much beds tilt down from horizontal, because the bed is horizontal it strikes in all directions, because the bed is horizontal, the dip is 0%, because the bed dips vertically (has a 90% dip), it dips equally in either direction at right angles to strike, so the dip line is shown extending in both directions, continental margins undergoing oblique (not straight on) plate convergence. The profile is a smooth curve where its gradient changes, rather than straight-line segments connecting the dots and only bending at the dots. The state(s) in which the quadrangle is located, The name and fractional scale of the quadrangle map that is located adjacent to the northeast of the corner corner, The longitude of the eastern boundary of the map, The latitude of the northern boundary of the map. Read about metamorphic rocks. The image above shows the northeastern corner portion of the topographic map of the Juniper quadrangle, which spans the border of the states of Oregon and Washington. A geologic map shows mappable rock units, mappable sediment units that cover up the rocks, and geologic structures such as faults and folds. Compare the profile to the topographic map. These symbols are stacked in age sequence from oldest at the bottom to youngest at the top. We’d love your input. It may help to imagine a vertical surface, such as a wall in your house. Second, geologic maps are essential tools for practical applications such as zoning, civil engineering, and hazard assessment. You can see that the grid, shown below, includes the range of elevations that the line of profile crosses on the map. The relief on a landscape is the elevation difference between two given points. Note that the vertical scale on the profile is very different from the horizontal scale on the map. Note that the ends of this profile go below the 400 foot contour elevation but they do not extend to the 380 foot elevation because on the map the line of profile did not reach the 380 foot contour line. Lower productivity of labour 3. The symbol for minutes is a single apostrophe: ‘. Also note that the top of the profile reaches a peak above 520 feet but less than 540 feet because the line of profile does not cross the 540 foot contour line. If you drew a profile from north to south across the peak of the hill, do you think the profile would be symmetric or asymmetric? Geologic maps are important for two reasons. Topographic maps reveal the shape of a landscape. Let’s look at metamorphic rocks next. In an actual view of the hill, looking at it from the side, it would not look nearly as steep as it does in the topographic profile that we have constructed. 2.1 Electrons, Protons, Neutrons, and Atoms, 4.5 Monitoring Volcanoes and Predicting Eruptions, 5.3 The Products of Weathering and Erosion, Chapter 6 Sediments and Sedimentary Rocks, 6.3 Depositional Environments and Sedimentary Basins, Chapter 7 Metamorphism and Metamorphic Rocks, 7.5 Contact Metamorphism and Hydrothermal Processes, 9.1 Understanding Earth through Seismology, 10.1 Alfred Wegener — the Father of Plate Tectonics, 10.2 Global Geological Models of the Early 20th Century, 10.3 Geological Renaissance of the Mid-20th Century, 10.4 Plates, Plate Motions, and Plate-Boundary Processes, 11.5 Forecasting Earthquakes and Minimizing Damage and Casualties, 15.1 Factors That Control Slope Stability, 15.3 Preventing, Delaying, Monitoring, and Mitigating Mass Wasting, Chapter 21 Geological History of Western Canada, 21.2 Western Canada during the Precambrian, Chapter 22 The Origin of Earth and the Solar System, 22.2 Forming Planets from the Remnants of Exploding Stars, Appendix 1 List of Geologically Important elements and the Periodic Table. True north is the direction toward the geographic North Pole. The explanations include descriptions with enough detail for any geologist to be able to recognize the units and learn how their ages were determined. The magnetic North Pole is in northeastern Canada. The point where each contour line crosses the line of profile on the topographic map determines the horizontal coordinate of each corresponding point on the grid of the topographic profile. 10- or 30-Hour Training Cards ... and is present in varying amounts in almost every type of mineral. If the vertical scale on a topographic profile is different from the map scale, as it is in this case, then the profile will exhibit a vertical exaggeration. Physical Geology by Steven Earle is licensed under a Creative Commons Attribution 4.0 International License, except where otherwise noted. Maps are as important in geology as written texts are in the study of literature. 5 Full PDFs related to this paper. When specifying a latitude, always state whether it is in the Northern Hemisphere (N) or Southern Hemisphere (S). Take the quiz. A geologic cross-section is a sideways view of a slice of the earth. Exercise 12.3  Putting Strike and Dip on a Map. The geographic North Pole is where the northern end of earth’s axis of rotation is located. These units, which divide angles into smaller parts, work as follows: Two common quadrangle sizes are 7.5 minutes (1/8 of a degree), and 15 minutes (1/4 of a degree). A topographic profile is similar to the view you have of a landscape while standing on earth, looking at hills and valleys from the side rather than from above. Earth scientists regularly use topographic, bathymetric, and geologic maps. In other words. 2. When specifying a longitude, state whether it is in the Western Hemisphere (W) or Eastern Hemisphere (E). If you walk perpendicular to contour lines what are you doing? What type of fault is this, and is this an extensional or compressional situation? For example, if the vertical scale on the profile is 1:200 and the map scale is 1:24,000, the vertical exaggeration is [latex]\displaystyle\frac{\left(\frac{1}{200}\right)}{\left(\frac{1}{24,000}\right)}[/latex]. Section 1.4 also presents the distinct moral hazards and ethical considerations associated with the scale of CDR in these IAMs. It shows how the different types of rock are layered or otherwise configured, and it portrays geologic structures beneath the earth’s surface, such as faults and folds. Draw a grid that will contain the profile. If you could push the wall so it’s leaning over, but still attached to the floor, the strike direction would be the same, but the dip angle would be less than 90˚. Contour lines curve upstream when they cross a valley. Latitude is how far north or south of the equator a point is on earth, measured in degrees, from 0° at the equator to 90° at the poles. In addition, the grid must have an extra horizontal line at the bottom and top to accommodate the parts of the profile that go above the highest contour elevation and below the lowest contour elevation. This cross-section shows seven tilted sedimentary layers (a to g), a fault, and a steeply dipping dyke. Standard United States Geological Survey topographic maps cover a quadrangle. The contour interval, the difference in elevation between adjacent contour lines on the map, is listed below the map scale as 20 feet. What do topographic maps do and how do they do it? It takes some training to read maps skillfully. When you know how to read contour lines, you can look at them on a topographic map and visualize the mountains, plains, ridges, or valleys that they portrays. Now that you have marked the elevation points on the profile grid, draw a smooth line connecting the data points as shown below. The map scale is listed in terms of the fractional scale as 1:24,000. To read a topographic map, you need to understand the rules of contour lines. Figure 12.19 Measurement of strike (left) and dip (right) using a geological compass with a clinometer. Alpha quartz is found in igneous, sedimentary, and metamorphic rock, and all soils contain at least a trace amount of quartz (Document ID 1334, p. 9). Topographic maps are important in geology because they portray the surface of the earth in detail. It shows depths in the Columbia River in feet below the surface of the river when the river is backed up in its reservoir behind a dam to a normal pool surface elevation of 340 feet above sea level.). As detailed in Section 1.4, matching the scale of CDR to hard-to-avoid emissions calls for gigatonne-scale removal – a large endeavor, though significantly less than the massive scale suggested by many IAM studies. This paper. The bathymetric map pictured in figure 3 shows the form of Loihi. A short summary of this paper. On the flank of Kilauea is an even younger volcano called Loihi. What are the meanings of the terms topographic map, contour line, contour interval and index contour? Topographic maps are also used by hikers, planners who make decisions on zoning and construction permits, government agencies involved in land use planning and hazard assessments, and civil engineers. By enabling player identifier, you'll know the real person behind the nickname in your game. The grid must extend high enough to span the elevation range of the contour lines spanned by the line of profile. If you took a magnetic compass to the Juniper quadrangle in 1962, its north arrow would point 20.5° east of true north, so you would have had to set your magnetic compass to compensate for the declination. Santa Claus is Coming to Town 4. That is why the grid in the example below goes below 400 feet and above 500 feet in elevation. It would be as if a rubber model of the landscape has been pulled in the vertical direction, until it is 120 times taller than it really is. View the animations. Faults and folds are also shown on geologic maps. The beds on the west (left) side of the map are dipping at various angles to the west. Topographic maps show the three-dimensional shape of the land and features on the surface of the earth. You will see that the hill is steeper on the west (left) side than on the east (right) side. For the map used in this example, we choose to draw the profile from A to A’ as shown in the diagram below, to see the entire length of the hill in profile. Click on How Rocks Change and read the introduction and the section about Heat and Pressure. Figure 12.20 shows an example of how we would depict the beds that make up an anticline on a map. Download PDF. First, as geologists make geologic maps and related explanations and cross-sections, they develop a theoretical understanding of the geology and geologic history of a given area. A geologic map shows the geological features of a region (see figure 4 for an example). The geology is superimposed on a topographic map to give a more complete view of the geology of the region. If the vertical scale of a topographic profile is different from the map scale, the vertical exaggeration should be listed next to the profile, such as VE = 10 or VE 10x if the vertical exaggeration is 10. KEY ENGLISH TEST for Schools Listening. By studying maps, a geologist can see the shape and geology of the earth’s surface and deduce the geological structures that lie hidden beneath the surface. The contour lines reveal the shape of the land in the vertical direction, allowing the 3-dimensional shape of the land to be portrayed on a 2-dimensional sheet of paper or computer screen. Degrees of latitude and longitude are divided into arc minutes and arc seconds. An example of how this is done is shown on Figure 12.19. This is consistent with the contour lines being spaced more closely on the west side of the hill and farther apart on the east side of the hill. Figure 4. The middle bed (light grey) is horizontal; this is denoted by a cross within a circle. In contrast, a degree of latitude remains approximately 69 miles across, no matter how near or far from the poles or equator it is. Circles that are closed contours generally signify hills. For example, to convert 15′ into a decimal fraction of a degree, 15′ x 1°/60′ = 0.25°. Mappable units are shown as different colors or patterns on a base map of the geographic area. A topographic map (like the one in figure 1) is one type of map used by geologists. Numbers are low near sea level and become higher with depth. Black lines in the inset show the land surface above sea level and blue lines show the topography below sea level. We'll track players' scores … When describing the dip it is important to include the direction. From the edge of the piece of paper, the data are transfered to the profile grid, which is on a separate piece of paper. Depressions that have no outlet are signified by closed contours with short lines that stick out of them and point toward the center. 12.4 Measuring Geological Structures Geologists take great pains to measure and record geological structures because they are critically important to understanding the geological history of a region. Read about metamorphic rocks.

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