Map+exercise+3_Winter+2019_JH 2023-11-18 17_13_26

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Geo 111 Lab Lab 7 Student name: _________________ Lab 7: Maps continued I. 3D imagination In the previous exercises you learned that a topo map helps you to imagine the landform in 3D. Some of the fundamental principles include: ● Evenly -spaced contours suggests uniform rate of change (i.e. uniform topographic slope). ● Closely -spaced contour lines indicate steep rate of change. ● Widely -spaced contour lines indicate gentle elevation gradient. QUESTION 1: Based on the above, match contour maps 1 to 6 (left) with profiles A to F (right). II. Ridges and valleys on topo maps The Rule of the V: As shown in the figure below, when contour lines cross a river or stream, they form a “V” shape that always points upstream. This helps you determine the direction of flow in a stream. The Rule of the V’s also applies to ridges. The top of a ridge is shown as an enclosed shape, like an irregular oval. As contour lines extend out from the ridge, they often form rows of parallel “V’s” that point downhill towards lower elevations. But “ V ’ s ” on valleys are more acute.

Geo 111 Lab Lab 7 QUESTION 2: Examine the topo map above and determine which way is uphill or downhill. a. If water is flowing in the canyon which way is it flowing? North, south, east, west, or other (specify). b. Mark the flow direction with an arrow. c. What is the length of the stream (within the map limits)? Show your calculation. III- Orientation: Geographic vs. Magnetic North The North Pole (also known as the Geographic North Pole) is the point on the Earth’s surface in the Northern Hemisphere about which the Earth rotates. It is one of the points where Earth’s imaginary axis intersects the surface. Latitude are centered upon the geographic north and south poles. Earth’s magnetic field has its own axis and Magnetic North Pole. The rotational and magnetic axes are not aligned, and the rotational and magnetic poles are therefore separated by several hundred miles (lower left figure).

Geo 111 Lab Lab 7 Compass needles always point to the magnetic north, but maps are aligned to the geographic north (also called true north). The angular difference between geographic north and magnetic north is called declination . Declination varies from 0° to 30° in most regions of the world. These declination values usually change slightly over time, as the magnetic pole wanders. QUESTION 3 . Examine the upper right figure which has been taken from a 1975 Canadian map. a) What was the declination in 1975? (Consider declination as the angle between Magnetic North and Grid North) b) What is the annual rate of change? Is the declination increasing or decreasing every year? IV. Direction and taking bearing By convention cartographers draw standard maps with north (N) at the top, and east (E) at the right. Regardless of if north is at the top or not, a standard map marks the direction of north by an arrow. A bearing is the direction from one point to another and is given in degrees (between 0° and 360°) relative to the geographic or magnetic north. We use a compass or a protractor for taking bearing. QUESTION 4. Give the bearing of point A to B located on the map below. (Diagram from Bush & Tasa, 2003, Laboratory Manual in Physical Geology, 6th Ed., AGI & NAGT)

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Geo 111 Lab Lab 7 V. Making topographic profile from a contour map (continued from previous lab activity) Scale: 1 inch = 1/4 mile

Geo 111 Lab Lab 7 QUESTION 5. Examine the map above and answer the following. Note that contour values are in feet. a. There are two types of contour lines, main and minor. By default the main contour line is twice the thickness of the minor. Determine the Main Contour Interval (C.I.)? b. What are the dashed lines? Could they be contour lines? If not, explain why they can ’ t be contours. What do they represent then? c. Give the elevations of points A, B, C, D, E, and F. d. From the verbal scale derive a ratio scale and a graphic scale. Show your operations in the space below. (Hint: 1 mile is equal to 63360 inches) e. What is the distance between points C and E? Show your calculations in the space below. Do not miss units. f. In the space provided below the topo map draw a profile along the line A-B using a vertical scale of 1” = 80’.

Geo 111 Lab Lab 7 VI. Strike and dip From your textbook for the lecture you learned that geology exists in three dimensions. Yet when we display it on a map, we see only two dimensions. To convey accurately the nature of geologic objects, we must use a shorthand notation to specify orientation in three dimensions. For a planar feature, its three-dimensional orientation is described by its strike and dip. Strike is the line formed by the intersection of a horizontal plane with the plane of the feature as shown in the following figures. The strike of a rock layer fixes its orientation with respect to compass direction. The angle the layer dips into the ground is its dip. It is always perpendicular to strike. To visualize strike and dip, consider a tilted board placed in a tub of water. The board’s strike corresponds to the line traced on the board by the surface of the water. The dip is the direction water slowly poured on the board would flow down. QUESTION 6. On the map related to QUESTION 5 draw a layer of sandstone trending N30°E and dipping 45°NW. Apply strike and dip symbol on the topo map using the guide above.

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