how to draw strike lines on a geologic map

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A geologic map represents the Earth's surface as it would appear looking straight down from above, . dtr changes degrees to radians. At this point, I finally introduce the concept of strike. Bedding planes and structural features such as faults, folds, are shown with strike and dip or trend and plunge symbols which give three-dimensional orientations features.. Stratigraphic contour lines may be used to illustrate the . Correction for Strike and Dip 1.4) from Unit 1, showing only bed F and the 300 m and 350 m contour lines. 300 1250 Fig. Given the elevation of 3 points on a geologic surface This is the first of three weekend mapping activities for a 4-credit hour introductory field course. Give the . Here, simply click the Save button on the toolbar or go to \\Model\Save, and then close the window. 12-03-2015 10:46 AM. The Three-Point Problem: Graphical Solution - Modified The azimuth of strike . Public Review Draft - Digital Cartographic Standard for Geologic Map Symbolization PostScript Implementati on (filename: of99-430_02-02.eps) REF NO DESCRIPTION SYMBOL CARTOGRAPHIC SPECIFICATIONS NOTES ON USAGE . First, let's look at how you can get a strike and dip measurement from a map symbol. . A line connecting the points of equal elevation along the geologic contact defines STRIKE 3. B Lines of strike can be determined by locating where a contact intersects a given contour line in more than one point; these points of intersection lie along strike. Translate each azimuth reading into a direction (e.g., northeast). plan view) with the appropriate strike-dip and anticline symbols. In most cases, i have seen cross-section lines that pass through dip-slip faults on geological maps and they are represented as displacement of lithologies along the fault plane on 2D cross . Geologists measure the orientation of rocks wherever they can find a suitable outcrop, using a compass and transit. Turning on and off the topo view with the Google Earth grid lines clicked -on will allow determination of what lines are longitude lines. Draw straight lines to link each photograph (A - G) with the locality (marked 1 - 15) on the map where you think it was taken. Table of Fold Symbols. A spread sheet containing dip/strike data If you're using ArcMap, add this table to the map using the Add Data tools found in ArcMap 10. Draw strike line at the precise orientation . orientations of lines and planes by following the procedures outlined above, except in reverse. Below is a simplified map of the geology around the fictional town of Rioville. West Virginia Geologic Handbook 74 The strike is now shown as line BD. Form-lines help the geologist to visualize the structure at the scale of the landscape and help them to identify key area such as large scale fold hinges, unconformities etc. Step 5 Fig. To measure the strike, draw a strike line where a topographic contour of your choice intersects your chosen lithologic contact. To do this, it is probably easiest to fold the scratch copy of the topographic map along the profile line (A-B). All the horizontal lines on a plane are parallel, so they all have the same characteristic compass direction. Figure 2.1 is a simplified version of the Greek Hills map (Fig. 4. Geologic map showing the position of two locations at which bedding attitudes were measured. N.B: The strike-slip fault in geology, is a plane of deformation which displaces a rock outcrop (object) horizontally (after splitting it into two parts). Use strike lines to calculate dips of faults or beds when not indicated by strike and dip measurements on the map. 1). They are used together to measure and document a structure's characteristics for study or for use on a geologic map. a. The contours are so detailed on the topographic map that you can just use every other contour to construct your profile. Geologic Maps: The Geologist's Indispensable Tool Author: James D. Myers Subject: Activity 1: Strike and Dip The short line indicates the dip direction, and the dip angle is written next to the symbol. To find a strike and dip of a formation or fault using a geologic map you can do what is known as a three-point problem. Step 2: Draw a straight line (Strike line) along the points of intersection of bedding plane and contour line. There are many other symbols and properties of geologic maps. Use to indicate another type . 11. Begin by using the down plunge method of viewing to visualize what your cross section will look like. Answer: Drawing Strike Lines A strike line is drawn by connecting the locations or points where the same set of lithological contacts intersect different parts of the same contour. 5). To determine the angle of dip . (3) Use fold line technique shown in e.g. You may remember the technique for drawing a topographic profile from your introductory geology course (Fig. The strike line of a bed, fault, or other planar feature, is a line representing the intersection of that feature with a horizontal plane. Dip is the angle that a bed or layer plunges into the Earth from the . Part 1. The dip of a fault is the perpendicular of the strike. the map pattern. 2. 3.6 to determine A geologic map or geological map is a special-purpose map made to show various geological features. The beds on the east side are dipping to the east. This strike can then be measured on the map using a protractor. Use the azimuth protractor in the back of the manual to draw the indicated strike lines on each compass. Sawteeth on upper (tectonically higher) plate. On a map, you can get the strike from this symbol by measuring the direction of the long line relative to north. The symbols on the cross section refer to strike and dip, a very important concept when reading geologic maps. Here's a small sample of a real geologic map. On the Label Rotation dialog box, type 90 in the Additional Rotation box. Prediction and interpretation is done to an area and field observations is to prove the results of the . Strike (4x4) Dip (4x4) 3b Draw four attitude symbols on the map that show the strike and dip of each feature (draw one for each feature). Determine true dip and apparent dip along the section. . Strike and dip is a measurement convention used to describe the orientation, or attitude, of a planar geologic feature.A feature's strike is the azimuth of an imagined horizontal line across the plane, and its dip is the angle of inclination measured downward from horizontal. . Figure 4: Style tab under Layer Properties where you can select SVG Marker as the layer type and then the appropriate joint symbol. N 0 . Information . Strike: The compass bearing of an imagined horizontal line across a plane. B are parallel and evenly spaced. So for example, if you see a contact line between two rock units on the geologic map that crosses the same topographic contour in two different locations, the line between those two points would be your strike. Figure 12.20 A depiction of an anticline and a dyke in cross-section (looking from the side) and in map view (a.k.a. . building a geologic map from scratch, and so many steps involving geodatabase construction and . 1 a. Show with an arrow () at each of the Water provides a horizontal surface. ArcCatalog layout, showing blank mapping geodatabase downloaded in Section 1.2 above. Draw straight lines to link each photograph (A - G) with the locality (marked 1 - 15) on the map where you think it was taken. Topographic map, showing technique for drawing a topographic profile along line AB. Let's look at another example. Geologists use a special symbol called strike and dip to represent inclined beds (Figure 2) . (3) Draw in the conventional map symbol for the structure that you identified in (2) above. Where space permits mark the strike in degrees (3 figs) at the correct end of the strike line. DIP: The angle formed by the intersection of a bedding or fault plane and the horizontal plane; measured in a vertical plane perpendicular to the strike. On a profile or a cross-section, the ratio of the vertical scale to the horizontal scale, expressed as a fraction, is the vertical exaggeration . Fasten the map to the drawing board or table with the line section in parallel on the lower edges of the drawing board or table Tape part map, a few centimeters below the line section, then the line of paper to do the plot lines of the section. Connect those . Skills Practiced. Labeling strike and dip. What's the strike and dip measurement for this map symbol . 2. A, Lineup the 0o-180o line of your protractor with the strike . Figure 7. Figure 2.1 is a simplified version of the Greek Hills map (Fig. You can also write some code to draw the strike line. This quiz and worksheet test you on the following skills: Defining key concepts - ensure that you can accurately describe terms like geologic map and topographic map. In addition to the contact lines, geologic maps contain symbols that represent key features, such as the dip and strike of the rock units, anticlines and synclines, and the traces of fault surfaces. 1 with either strike or dip. The lines correspond to the height contours on a topographic map and are known as structure contours. The areas underlain by each unit are indicated on geologic maps by polygonal areas with distinctive fill colors and patterns. The dip gives the steepest angle of descent of a tilted bed or feature relative to a horizontal plane, and is given by the number (0-90) as well as a letter (N,S,E,W) with rough direction in which the bed is dipping downwards. IV Appearance of planar beds on a geologic map A Planar beds have a constant strike and a constant dip B Strike lines along structure . Determine the strike of each layer and enter it in the blanks above each map. Figure 1.4 (Greek Hills Map Area) shows a geological map with the topographic map from . In fact, I am a PhD student in geology. In addition you will be drawing and reading standard geologic map symbols for faults, folds, and strikes and dips. You see a strike and dip symbol on a geologic map. Form lines can be seen on aerial photographs, therefore form lines seen in the field can be extrapolated relatively easily to a large area. Draw the lines joining points of equal depth on the surface. Use the Maplex Label Engine's Additional Rotation option to rotate the label to match the rotation of the dip symbol.. Figure 11. perpendicular to the strike line (AA' and CC') Second, draw the right triangle, BDC'. a plunging fold) the bearing may change systematically over the fold. [SE] The beds on the west (left) side of the map are dipping at various angles to the west. The long line is oriented along the strike direction. The dip angle for the beds is measured from the horizontal surface to the uppermost dipping bed, perpendicular to the strike line. Geological maps are typically divided into areas of different colours (for different rock units) that are bounded by lines; these lines on the map are the traces of the geological surfaces that separate the units. All of that is on the map's base. . On the cross section, you must label your x and y axes, show topography from A to A', label all 4 . Use medium-weight blue lines for fold hinges. Figure 8.7 | Strike and dip for tilted sedimentary beds. Refer to the Lab Assignments Grading Rubric for a reminder of what constitutes a well-performed lab. To measure the strike, draw a strike line where a topographic contour of your choice intersects your chosen lithologic contact. When measuring strike and dip from a geological map, use one contact, and . About Press Copyright Contact us Creators Advertise Developers Terms Privacy Policy & Safety How YouTube works Test new features Press Copyright Contact us Creators . On your geologic map, depict the hinge lines of folds at the point of maximum curvature and be sure that your strike-and-dip data support the interpretation. Although the two-dimensional map-view is useful, one of a geologist's key tasks is to infer the type and orientation of rocks in the subsurface. Then the distance between them along XY line is measured. To draw your line, use the Interpolate Line button and start clicking out a . This first strike line drawn is designated as the reference strike line. The short lines with numbers next to them are strike-and-dip symbols. To determine the structural gradient or dip, we must know the map distance (horizontal distance) over which that geologic surface drops 100' in elevation. strike-slip faults in map view) to show thrust offset. Geologic maps that display strike and dip symbols require the label to be rotated with the symbol. Geologic maps are maps that depict the rock units that crop out at Earth's surface. Choose Geographic for Rotation Type. Set the label offset to be 2 points, measured from the feature geometry. Find two contour lines (elevation 1 and 2) that cross both the upper and lower contact of a given bed (1) For elevation 1, draw two strike lines, one for the upper and one for the lower contact (2) For elevation 2, draw two strike lines, one the the upper and one for the lower contact. A Geologic Map Exercise. Example 1. Measure the distance between the strike lines on the map, and using the map scale, convert your measurement (say, 10 mm) to a map distance (say, 225'). And a line having the same length is drawn on the drawing paper somewhere below the profile already made. Strike and dip are a way of representing the three-dimensional orientation of a planar surface on a two-dimensional map. 3). Find the closest longitude line to your strike line. To determine dip, a new point E is established at some distance that will create a perpendicular line to the lowest elevation point A. To determine the strike, measure the angle between your constructed strike lines and the North direction on the map. building a geologic map from scratch, and so many steps involving geodatabase construction and . Strike and dip measurements of geologic features are measured using either the Move Clino iPhone app or a Brunton pocket transit. Exercise 4: Reading Geological Maps (PDF) 25-27 Lab 6: Geologic Mapping (PDF) Example Stratigraphic Column (PDF) Base Map (PDF) 28-29 Lab 7: Rivers (PDF) 35 Exercise 5: Science, Policy, and Public Opinion (PDF) Course Info. Viewing the results in Google Earth 3D (left) helps students visualize their constructed dip lines and the two horizontal lines they've drawn. In Figure 9, the strike is north-south (= 000 = 180 ). Below is a diagram explaining strike and dip. Assume all folds plunges 8 o eastward. Measure distances BD, DC', AA', and CC'. Draw the line section (A-B) on face of the map. Strike and dip refer to the orientation or attitude of a geologic feature. a. Calculating Dip By definition, dip is perpendicular to strike, and by using the Rule of V's (Figure 7) you can determine the direction of dip. On a geologic map, this is represented with a short straight line segment oriented parallel to the strike line. Two Strike lines from contours of different values are drawn for the same boundary. Right click the tool \\Geologic Mapping Tools\ (2) Apply Coordinate System to ESRI_Geology.gdb, and select Edit to bring up model flow chart (Fig. The line of strike is represented by the water line when a lake intersects with the rock along the shoreline (Figure 8.7). Geological mapwork: using surface geology to make a geological map Match the photos to a map to see how a geological map works For each of the photographs: 1. Navigate to "Add XY Data" Figure 4. Take same geologic contact, and identify another (different) topographic contour line that crosses at two points, draw a line between them (1) You now have two strike lines on the same geologic bed (2) draw a line perpendicular to . Finally add some code to draw a line from the coordinates for the dip lines. They represent the plot of horizontal lines on the bed and thus mark its strike. Figure 3. To add strike and dip symbols to your map, you need to open up the Properties - Style dialog box of your point layer, select SVG Markers and select the appropriate symbol in the Joints folder (Figure 4). First, examine the map key and note the relative age of the various units. When measuring strike and dip from a geological map, use one contact, and . Structure contours from outcrop patterns Draw strike lines for the limestone bed Clue 1: Join points on the outcrop which share the same height. (It is armed with a number of ideas about the geology developed from looking at published maps, literature, satellite image, aerial photographs, topographic map and/or gravity map). A parallel strike line is constructed wh. For homework, students define mappable units, locate contacts, create a geologic sketch map, add strikes and dips, and work out which unit is the . Below is a geologic map showing the position of two outcrops in which the attitude of bedding was measured (Figure 12). geologists have continued to draw cross-sections, and continued the practice of using color (or patterns) to distinguish different geologic units or formations. 12-03-2015 10:46 AM. On the geologic map, you must show and label the lines of strike (at least 2 lines per contact) and the strike angle. On a geologic map, this is represented with a short straight line segment oriented parallel to the strike line. The scale is the length of the dip line you would want (the bigger the area, the larger the scale). Once this line AE is established, dip angle can be calculated by the following equation: 2. So, to find the orientation of lines plotted on a stereonet projection: 1) Rotate the net until the point lies on the E-W meridian. Finally add some code to draw a line from the coordinates for the dip lines. Some geologic maps have multiple cross-sections, and will include all of these on a separate page or on an expanded map sheet. Drawing strike and dip symbols is important when you make a geologic map.d. (4x3) 3c Draw a line through the radio tower showing the orientation of a vertical cross section 2. You can also write some code to draw the strike line. These give us the third dimension of the rock layersthe direction they extend into the ground. 1. This is easiest where a contact is steep. Open ArcCatalog from the Start Menu and navigate to the file geodatabase "ESRI_Geology.gdb" in your project folder (Fig. . Like the real thing, mapping this relatively simple geology (a single panel of uniformly dipping rock units) as a starting point for later exercises can build confidence and be used to address conventional, mundane map-making issues (orienting a map, plotting measurements, drafting, labeling . You can see the basic things discussed earlierthe shorelines, roads, towns, buildings and bordersin gray. Then, I would like to move (displace) the outcrops (contours) existing on the right side of the fault (line), along the fault line itself (which is not perfectly straight), so that those right outcrops join their . The short trunk represents the dip and the top line represents the strike . Strike and dip map symbols look like the capital letter T, with a short trunk and extra-wide top line. The structure contours in Fig. The angle of the strike is shown on each map. Geologic Maps Homework Assignment #1 1. [CC] Physical Geology: Structure, strike and dip The Creation of a Geologic Map Map 13 video 9 Calculating strike and dip Strike Lines to find Strike and Dip 2018 Geologic Map Compilation (7): Geologic Cross Section Help video for calculating dip 3.1.3a Strike and Dip Map 13 video 4 . dtr changes degrees to radians. Strike Line Protractor Base e Step 20: In the topo view find the north-south longitude lines. Geological mapping is a process of problem solving. 1.4) from Unit 1, showing only bed F and the 300 m and 350 m contour lines. Indicate the strike of the darker bed on the geologic maps shown below in Fig. Draw another strike line for the same bedding plane with consecutive contour to calculate the dip of the bed and direction. Any red "x" that was on the tool should be gone now in ArcToolbox. The strike is the compass direction of a horizontal line on the plane. Introduction to Geologic Mapping. The intersection of a fault plane with a planar rock unit that the fault displaces produces a line called the fault cut-off or cutoff. Rock units or geologic strata are shown by color or symbols. STRIKE: The direction of the line formed by the intersection of a horizontal plane with a bedding or fault plane. It is known as the system of multiple working hypotheses. The strike of a fault is the direction that the fault runs. Draw a geologic cross section, including topography, on the attached figures from A to A' with no vertical exaggeration. a. To Determine Dip a. Locate the symbols where you collected information to determine the strike and dip of the features. You may need to Connect to Folder if you do not see the path in the Catalog Tree. The two map views in Fig. Label the arrows in Fig. The geologic part consists of the black lines, symbols and . The goal here is to complete a geologic cross-section along the line A-A', which crosses the Hoback Fault in order to figure out how much offset 2 N 550 N 300 I would like to draw a geologic map with contours (representing the outcrops) and a line (representing the strike-slip fault). d. Check the Keep label upright (may flip) check box. Strike and Dip Symbols. The contours are there too, in brown, plus the symbols for various water features in blue. 2 show the outcrop pattern of a single rock layer. map and cross section How to read geologic maps (And more!) If the plane is flat there is an infinite number of strike lines, all having the same dip (zero) but different bearings. The trend of the rock/fault outcrop. By navigating to File > Add Data > Add XY Data define which column hosts the X, Y and Z coordinates and import the data as locations on the map. This map, the Camp Davis Quadrangle, shows the geology at the southern end of Jackson Hole, a beautiful valley along the eastern edge of the Grand Teton Mountains. These join lines are structure contours for that particular height Clue 2: Draw as many structure contours as possible to test the assumption of constant dip (planarity of surface). The scale is the length of the dip line you would want (the bigger the area, the larger the scale). c. Choose Horizontal under Alignment Type. Strike and dip of Joints Strike and dip of faults dart and arrows indicate dip and strike separation directions respectively Planar measurements Mark the dip in degrees as near to dip tick as possible. Geological mapwork: using surface geology to make a geological map Match the photos to a map to see how a geological map works For each of the photographs: 1. b. Figure 3. Strike and dip measurements of geologic features are measured using either the Move Clino iPhone app or a Brunton pocket transit. Then line up the profile line A-B on this folded edge with the profile grid on the sheet that has your final copy. The line of strike is the intersection between the bedding plane and the horizontal plane . To draw your line, use the Interpolate Line button and start clicking out a . A geologic cross-section will be labeled on the map itself with a bold line and letters marking either end of the cross-section, usually with A-A', B-B', etc. Making Geologic Maps Map Units In making a geologic map, the geologist must recognize or define units or rock or surficial sediment that can be differentiated and mapped.