UNIT 5. INTRODUCTION TO FIELD MEASUREMENTS WITH THE BRUNTON COMPASS

Transcription

1 UNIT 5. INTRODUCTION TO FIELD MEASUREMENTS WITH THE BRUNTON COMPASS Topic A: Components of a Brunton compass (20 points) Topic B: Setting the local magnetic declination on a Brunton compass (check Bruntons) Topic C: Reading the graduated circle (A BEARING) on the Brunton (30 points) Topic D: Calculating distance by pacing (10 points) Topic E: Taking a bearing reading and pacing from a common point to two distant points and back shooting to return, using the Brunton in the field (outside) An Expansion of Topic C (20 points) Topic F: How to record and draw Strike and Dip (25 points) Topic G: Measuring the thicknesses of dipping strata using a Jacob staff (20 points) Topic H: Determine the height of an object on level ground, using the Brunton (10 points) Topic I: Create a round-trip traverse map using a Brunton and pacing (20 points) 1. RATIONALE: Students will explain the components of the Brunton compass and be able to apply the instrument for various field uses. 6/21/14 ll. Topics, Objectives, and Learning Activities Topic A: Components of a Brunton compass Objective for Topic A: Demonstrate understanding of the various components of a Brunton compass (sometimes referred to as the Brunton Pocket Transit ). Equipment and Location A: Geology lab, tablet, Brunton compasses with carry cases, Brunton information pamphlet Introduction: The Brunton compass is one of the most fundamental hand instruments used by a field geologist. Students must have a thorough knowledge of the components, field use and field limitations of a Brunton compass. Learning Activities for Topic A: - Bruntons are expensive (+$300), use carefully and always carry in its leather case when not in use - Carry in the case with the mirror next to your body to prevent accidently hitting the most vulnerable part of the compass the mirror. - Do not use the enclosed mirror for shaving or make-up but can be used to flash rescuers when you are lost or hurt - Use the finger hole at the bottom of the carry case to push up and remove the compass - Examine the external components of the compass, to include external level arm (Vernier adjustment arm) on back (slide it back and forth), and external screw head (circular adjustment screw) on the side to be used to correct for magnetic declination (use to be explained later) - Notice the small oval-shaped glass window - To open - rotate the Brunton until the flat cover faces up and the small window is positioned away from you. Lift the top cover from the base of the Brunton. 1

2 - A description of the components of a Brunton compass can be found with the Brunton company manual (Goggle on tablet: Kooter s geology tools how to use a Brunton pocket transit ; scroll all the way down and click on the Adobe PDF file Brunton Pocket Transit Users Instruction Manual. (Azimuth or bearings) Clinometer Scale and % grade scale (reversed on some) (Not on all Bruntons) (Sapphire for smooth turning) - Review the names of all the components of the Brunton (as seen on the Brunton and web site image) with the Brunton sitting on the table - You can order Bruntons with an Azimuth graduated circle (zero to 360 degrees). With an azimuth, you would give an example direction as 60 degrees (60 0 ) - You can order Bruntons with a Bearing graduated circle (quadrants of 90 degrees). With a bearing, you would give an example direction of N 60 degrees E (N60 - Another example of a bearing direction could be N60 or opposite S60 W - The North end of the magnetic needle can be painted red or white. - Some Bruntons have a wire is wound on the needle opposite of the North indicating arrow this is to compensate for the magnetic field pulling the needle down - North is designated in a number of ways on different Bruntons (on bottom) but most have either a fleur de lis or a five-point star. - Notice and explain the placement of the West and East on the graduated circle because the Brunton is a direct reading compass. - All readings for direction must be taken with the bubble in the center of the bull s eye (i.e. the compass must be level or your compass directions will be incorrect - Also important to understand the use of the lift pin for recording a reading: with the open Brunton sitting on the table and the bull s eye bubble is level press down on the lift pin and hold now you can take a reading without the compass needle moving 2

3 - Now for the clinometer (Vernier): while holding the Brunton in your hand, reach behind it with your finger and you will find the clinometer (Vernier) arm push it back and forth. Looking at the front of the Brunton, notice on the bottom or top for some) the clinometer scale that goes from zero to 90 degrees for vertical inclination or dip; on the inside (or on the bottom) is a scale that reads from zero to 100% grade. In the middle is a Vernier scale to take dip readings in degrees to the nearest 10 minutes (rarely used to this accuracy by geologists today). - Now set the open Brunton on a table, on its side, with the clinometer level up (West down); reach behind the Brunton to find the clinometer arm and rotate until you see the bubble centered in the clinometer level (which should be level at zero degrees). - Discuss and demonstrate effects of nearby power lines, cell phones, nearby magnets, magnetite deposits, nearby generators, reading within cars, trucks and other vehicles - Very useful reference is the Brunton Compass User s on-line Manualhttp://kooters.com/pdf/BruntonTransit-inst.pdf lll. Evaluation of A: :Ask students to point to various components of a Brunton, as I ask for locations of component parts. Unit 5 Topic A Quiz 15, using a picture of the Brunton, where students will label components (tentative 20 points). Topic B: Setting the local magnetic declination on a Brunton compass Objective for Topic B: Setting the Brunton compass for a region s magnetic declination. Equipment and Location B: Geology lab, tablet, Brunton compasses; small paper clip, cell phone apps if students have downloaded such Introduction B: The Brunton compass is one of the most fundamental hand instruments used by a field geologist. Knowing the area s magnetic declination and the setting of the Brunton to correct for this phenomena must be keep in mind when changing locations. Learning Activities for Topic B: - Each Brunton will be reset to zero declination before starting the exercise - From your notes with Unit 7, find the magnetic declination of an area, especially Corpus for Christi and Llano, TX - Then correct the Brunton for magnetic declination accordingly for Corpus Christi - Make sure students set the Brunton to a magnetic declination for Corpus Christi by using the side screw (usually a small paper clip is useful for turning the side-wall screw) - Note: some Bruntons have a top screw that must be made loose before adjusting the side screw (afterwards re-tighten this top screw) - Make sure the new setting is in the correct direction (East or West) - Compare your corrected Brunton direction to that of a cell phone app (in the classroom, expect to see a lot of magnetic interference) 3

4 lll. Evaluation B: Check that each student can properly find and set a Brunton for correct magnetic declination setting. Topic C: Reading the graduated circle (A BEARING) on the Brunton Objective for Topic C: Utilize the Brunton techniques to determine directions (bearing) to various points from your location Equipment and Location C: Geology lab only, tablet, Brunton compasses; some cell phone apps have a compass that could be used for comparative purposes if students have downloaded such an app. (Topic G will expand on this but will be done outside) Introduction C: Using the Brunton with two different methods: waist level and eye level All geologists understand how to read the bearings of a Brunton for directions and this is critical in the use of this compass. Students will work in pairs to assist one another in the learning process, with each student completing the process. Learning Activities for Topic C: -Reading the graduated circle or compass card: - On a flat table, open the Brunton and unfold the sighting arm to a flat position but have the mirror at a right angle or vertical direction and the long arm pointed toward the object. - Looking directly down on the Brunton, slowly spin the Brunton several times and notice that the white arrow always points in the same direction (magnetic North) if there is no magnetic interference in the room - Rotate the Brunton until the white need points to index pin this is magnetic North (because of your declination settings) - #1. Looking directly down on the Brunton on the table and the back of the Brunton must be in front of you and the extended lever arm pointed away from you (you will have to move around the table), slowly rotate the Brunton until the white needle points the bearing of North (azimuth zero degrees) this is True North (or the axis of Earth s rotation); here notice that the extended lever arm is pointing North. 4

5 NOW, tilt the mirror back toward you (see picture) find an object in the room that lines up with the mirror center line and the folded peep sight on the extended arm. Thus you pin-point an object that is due North from your position! And you can walk to the actual object that has a bearing due North of you! MEMORIZE THIS RULE: IF THE EXTENDED ARM POINTS TO THE OBJECT, TAKE YOUR READINGS FROM THE WHITE (RED) OR NORTH ARROW - #2. Same exercise, different direction. With the back of the Brunton in front of you and the extended lever arm away from you (you will have to move around the table), rotate the Brunton to the left until the white needle points to the bearing of West (azimuth of 90 0 ); notice that the extended lever arm is now pointing West (the direction that you are looking). NOW, tilt the mirror back toward you (see picture) find an object in the room that lines up with the mirror center line and the folded peep sight on the extended arm. Thus you have found an object that has a bearing that is due West from your position! And you can walk to that object that is due West of you! - #3. Same exercise, different direction. With the back of the Brunton in front of you (you have to move around the table), now rotate the Brunton to the right until the white needle points to the bearing of S45 0 E, (azimuth of 135 o ) notice that the extended lever arm is now pointing West (the direction that you are looking). Thus you have found an object with a bearing that is S45 o E from your position! And you can walk directly to that object! - FOR THE NEXT EXERCISES THE BRUNTON IS TO BE HAND HELD - Practice leveling the compass in your hand at waist level for a direction (mirror against your body) and read the direction of the white (red) arrow. This can be a real challenge for beginning geologists! - With #1, 2 and 3 you were looking down on the compass, the table held the Brunton level. - Now let s do the same exercises as above but this time, you hold the Brunton in your hand (as shown in the picture below) and you must keep the Brunton level. 5

6 - (Sighting or lever arm would be flat for objects that are eye level; but for objects above eye level, the sighting or lever arm would be folded upwards as shown in the left picture. - #4. This time you are going to pick two objects on the other side of the room and you are to determine compass bearings from your position to these two objects (one at a time of course). - Similar to # above to practice leveling, align the white needle to various bearing directions: a. with the Brunton in your hand at waist level, b. with the mirror pointed away from your body, c. look down on the compass AND d. keep the bubble within the Bulls eye (Brunton is now level) - #5. Find the distant object in the mirror at this waist-high level, align the object with the line on the mirror with the extended lever sight AND maintain the bubble in the center of the Bull s eye as with step #4. (IF THE BRUNTON BULL S EYE IS NOT LEVEL YOUR COMPASS BEARING DIRECTION FROM YOUR POSITION TO YOUR DESIRED OBJECT IS WRONG!) Record these two bearings (and the type of object was) in your field book. - Normally for me, once I have needle calm and lined up, I gently press down and hold on the lift pin, (which locks the needle in place) so that I can record my reading for my bearing. - NEXT: OBTAINING A BEARING TO AN OBJECT THAT IS BELOW YOUR EYE LEVEL (This is used when there are too many objects (such as brush) that do not allow you to take a reading at waist level. This method is also used when an object is more than 15 degrees below the observer. MEMORIZE THIS RULE: IF THE EXTENDED ARM POINTS TO YOU, TAKE YOUR READINGS FROM THE NON-PAINTED (BLACK) OR SOUTH ARROW - #6. Find the bearing of an object for at least two objects that is low on the floor: a. with the Brunton in your hand at waist level (as shown in the above picture), b. and the mirror pointed toward your body, c. align the sights to as shown in the picture above with your target, d. keep 6

7 the bubble within the Bulls eye (Brunton is now level), e. now take your reading from the South arrow and record your bearing (this is a skill that takes a lot of practice) - NEXT: OBTAINING A BEARING TO AN OBJECT WITH THE BRUNTON AT YOUR EYE LEVEL (This is used when there are too many objects (such as brush) that do not allow you to take a reading at waist level. - #7. Find the bearing for at least two objects eye level somewhere in the room: a. with the Brunton in your hand at eye level (as shown in the above picture), b. and the mirror pointed toward your body, c. align the long arm sight with the black line on the mirror peep hole with your target, as shown in the picture above, d. keep the bubble within the Bulls eye (Brunton is now level), e. now take your reading from the South arrow and record your bearing (this is a skill that takes a lot of practice) - NOTE THAT THESE EXERCISES TAKE A LOT OF PRACTICE AND PATIENCE TO GET CORRECT BEARING DIRECTIONS USING A BRUNTON - #8. There are Apps for cell phones such as Compass and GeoCompass that can be quite useful to check your Brunton bearings (should be close). This assumes that you can get phone service at your mapping site which can be a problem. The further your target is from the cell phone, the less accurate your reading will be because you do not have peep sights for more accurate. alignments. Note that most free Apps come with advertisement banners and has fewer useful bells and whistles so paying for a good App is worth it. lll. Evaluation C: Unit 5 Topic C Quiz 16; on procedures of obtaining bearings with a Brunton (tentative 30 points) Topic D: Calculating distance by pacing Objective for Topic D: Apply the pace techniques to assess pace length for mapping purposes Equipment and Location D: Pacing outside the Coles Bldg.; use a cloth tape to measure 300 feet for pacing practice; a topofil reel (that measures in feet) to measure a longer traverse at the West campus; calculator, safety vests Introduction D: Geologists often use pacing methods to confirm relative distances, when other methods are not so practical and when GPS units are not available. 7

8 Learning Activities for Topic D: - There is one-step pacing (where you count every step) and two-step pacing (where you count every left or every right step) - For this exercise, let s use every two steps is a pace - I have measured out a 300 feet distance in front of the Garcia & Coles Buildings sidewalk - Record in your field book the number of paces for each 300 feet distance - Practice several traverses (at least separate 3 round trips) to get you average pace length - (For me, every two steps is a distance that is very close to 5 feet) - After the exercise, we will return to the classroom and you will calculate your average pace length. - Example: First 300 = 61 paces, Second 300 = 59 paces, third 300 = 60 paces, etc. for the three round trip would give me an average of five feet per pace. - Finally, I have discovered that most geology students have not had a drafting class and are unfamiliar with the engineer triangle scale or metric triangular scale. - For example, if you were to draw a line from 0-3 on the 30 scale this can represent: a line 3 feet long (scale 1 = 1 ) or 30 feet long (scale 1 = 10 ) or 300 long (scale 1 = 100 ) or 3,000 long (scale 1 = 1,000 ). lll. Evaluation D: From the pacing exercise and lighthouse estimation and scale line drawings, grade the entries and accuracy of the calculations in students field book and Unit 5 Topic D Quiz #17. (tentative 10 points). Topic E: Taking a bearing reading and pacing from a common point to two distant points and back shooting to return, using the Brunton in the field (outside) Objective for Topic E: Utilize the Brunton and pacing techniques to determine bearings back and forth from a common location in the field, using both eye-level and waist-level methods. This is basically a practice to later preparing a Brunton traverse map. Equipment and Location E: Outside the building, small plastic scale, Brunton compasses for field measurements; some cell phone apps have a compass that could be used for comparative purposes if students have downloaded such an app., safety vest Introduction E: It is not uncommon to use both waist-level and eye-level techniques during a traverse in the field. Back shooting or taking a bearing back to the point you just left, is just good practice in the field and can rapidly point to any errors during each of these readings. Learning Activities for Topic E: - Any drawings during this exercise are to be scaled at one inch equals thirty feet - #1. From point A, students are to use the Brunton for waist-level sighting, to obtain a bearing to a point B that is more than an estimated 100 feet away, and enter the bearing into their field 8

9 book. (If you have a phone app, take a reading to point A and also record this number but do not use the phone as you walk to point B) - With the Brunton folded in its case, as the student paces to the point B, they are to stop and make note of at least two objects that lie at right angles alongside their path to point B (see sketch map at the end of Topic F) and enter a description of these objects in their field book as they pass by each of these two objects. - #2. After pacing and arriving to point B, the students are to back-shoot the bearing back to point A, but this time use eye-level sighting. Enter the bearing into their field book. Then the students are to reconfirm their paced distance back to point A and the back paced distance of the two previous selected points along their traverse. (If you have a phone app, use it also for your back shoot.) - After returning to point A, the students are to pick another point that is at least 90 o from here to point C and repeat steps #1 and #2 again. - This is true multi-tasking because many things must be done at the same time: First (when sighting the Brunton) the compass must be level in the Bull s eye, second the point sighted must be exactly in the sights and third the needle must be brought to rest (all of which takes practice) to take a bearing. Fourth, then as you are keeping track of your pacing, you must also stop to make observations of other objects. - After completion, write a short evaluation of the cause of any inconsistencies or possible errors into your field book along with a sketch. - Normally for me, once I have needle calm and lined up, I gently press down and hold on the lift pin, (which locks the needle in place) so that I can take my readings. Also, there will almost always be inconsistencies (usually minor), but you do need to be aware of their possibilities 9

10 - Example of a map for Unit 5 Topic F mapping exercise - Notice that there is a slight difference when back shooting because the Brunton and our pacing is not that exact, but good enough to use for a map. lll. Evaluation E: Evaluate the thoroughness of the data entry and sketches on Unit 5 Topic E Quiz #18 and attached map (tentative 20 points). Topic F: How to record and Strike and Dip (Practicing in the lab then to the field outside) Objective for Topic F: Utilize the Brunton techniques to assess the strike and dip of a geological structure and accurately draw these symbols on a map or paper. Equipment and Location F: Geology lab, tablet, Brunton compasses and four sets of dip and strike wooden models in the lab and to the DMC East Campus lighthouse rocks for field measurements; cell phone apps if students have downloaded such; safety vests. (DMC East Campus Lighthouse is at the corner of Baldwin and Ayers, by the traffic light). 10

11 Introduction F: Although most geological structures are generally curvilinear or curviplanar, they can be approximated as linear or planar for specific scales. The Brunton compass is one of the most fundamental hand instruments used by a field geologist. Students must have a thorough knowledge of the taking strikes and dips (orientations) of geological structures. Students may want to view UT Austin website with pictures in taking strike and dip (ignore beyond the strike and dip) ( which uses azimuth instead of bearing). Another useful website is There are many cell phone Apps that can also be used for strike and dip readings (apps for a fee come without advertising banners). I have found these Apps fairly accurate and I use my phone to double check my Brunton readings (if I have cell phone service). Learning Activities for Topic F: - Generalities: - Make sure you are measuring a bedding plane or a fault plane and not just a irregularly weathered surface - Horizontal layers do not have a strike and their dip is zero. - In some aspects, all Brunton readings for a strike involves a water level and a dip involves a perpendicular to the water level - Strikes are taken from a horizontal plane (water level as if it were alongside a lake) and you must use the bull s eye level to be sure the Brunton is level - Dips are taken perpendicular to the strike direction and will be the maximum angle from the horizontal by using the clinometer level - Remember that the dip also has a compass direction which must be given unless it is zero or vertical - For recording a strike direction, some groups (but not all) use the right-hand rule for consistency. - RIGHT HAND RULE: place your right hand with your fingers pointing down dip your thumb will thus point to the strike direction (the direction of the extended sighting arm) 11

12 - Reading a strike: - Unfold the Brunton and sighting arm and place the bottom outside edge against the rock surface (except for the Brunton edge, your fingers will be under the compass) - Sometimes it is easier to place your field book against a rock to get a smoother surface (or a larger surface) - Adjust the compass orientation, making sure the bottom edge is always flat (water level) against the rock surface until the bubble in the Bull s eye is level then gently press the lift pin to lock the needle then read and record the needle value or strike direction - Several readings for strike measurements are recommended (including readings taken from the models in the lab). - Reading a dip: - After determining the strike, rotate the compass 90 o and place the flat side of the Brunton against the rock (generally with the mirror down dip) - Adjust the clinometer lever on the back of the Brunton with your finger until the bubble in the clinometer is level, record the reading of the dip. The direction of a dip can be thought of as the direction water would down the plane (i.e. N, S, E, W, NE, SW, etc.), so you can generally point and your Brunton dip direction with the white (red or North) arrow 12

13 - A dip is a maximum angle of inclination; any dip angle less than the maximum is called an apparent angle (which in most cases we have no interest) - Several readings for dip measurements are recommended (including readings taken from the models in the lab). - Taking strike and dip measurements in the field - When at the lighthouse, students will pick a minimum of three different dipping angle rock slabs and record the strike direction, dip angles and dip directions of each slab (also make a sketch of the relative location of the slabs in case you need to return and take another reading.) All of this is to be recorded in your field book. - Notice the variations in strike and dip because of the roughness of the rock slabs you should take readings at different locations on each slab to get an average strike and dip. - If you take a strike and dip using the app on your cell phone, record and compare your app readings to the Brunton readings, if different write down what you think might be the causes? - Drawing a strike and dip symbol - Example: Drawing a strike dip symbol for strike N60 o E, dip 75 o to the SE - To accurately draw strike and dip symbols, you need a protractor. - Notice how I drew the strike direction 60 degree East of North - THE DIP ANGLE IS ALWAYS DRAW PERPENDICULAR TO THE STRIKE SYMBOL 13

14 - Notice that the dip line was draw toward the SE quadrant (if it had been NW, it would have been drawn in the opposite direction) - You would NEVER draw the dip direction 75 degrees from the strike line the dip line is always drawn perpendicular to the strike line! - By the lighthouse, after taking strike and dip measurements, we will estimate the distance to a tree by looking, then by pacing to the tree. You will record both of your estimates (looking and pacing) in your field book. - I will introduce you to an instrument called a topofil reel to accurately measure that distance. Compare your paced distance to the topofil distance measured. lll. Evaluation F: From the lighthouse slab readings, grade the labeling and accuracy of the strikes and dips taken and recorded in the field book and drawn on a Unit 5 Topic F Quiz #19 Worksheet. (tentative 25 points). Topic G: Measuring the thicknesses of dipping strata using a Jacob staff Objective for Topic G: Utilizing a Jacob s Staff and Brunton to determine strata thickness Equipment and Location G: Brunton compasses, some sticks for Jacob s Staff, East and West Campus, safety vests, cloth tape Introduction G: Determining the thickness of strata, especially dipping strata is an important part of field activity. Geologists often use a Jacob s Staff to measure a stratigraphic thickness. Learning Activities for Topic G: - Jacob Staff: - You can make an emergency Jacob s Staff in the field by cutting a stalk from a yucca bush or any other straight tree or shrub branch. - If driving through town, stop at a hardware store and buy a 1 x 2 stick of lumber 5 long or one-inch thick, round stick (make sure the top of the stick is cut 90 degrees to a five foot length. - If you are using the English System of measurement (feet) cut the stick exactly five feet long MINUS 1 3/8 inch to compensate for the half-width of the Brunton - If using the metric system, cut a stick 1.5 meters long MINUS the half-width of the Brunton because the Brunton will be placed on top of the staff - Measuring stratigraphic section using a Jacob Staff General Rules: - It is easy to measure the thickness of flat-lying rocks (zero dip); you just put a ruler next to them and measure the strata from bottom to top. - For beds that have been tilted, more care is needed. - Measurements must always be made perpendicular to the strike of the bedding - You must always measure down dip, when measuring stratigraphic thickness (i.e. you see the beds dipping down away from your feet not dipping toward your feet). 14

15 - The steepness angle of the hill side and the dip angles of the strata relative to the hillside angle BOTH have an effect on the accuracy of your measurements (see figure 2 below) - For steep dipping beds under very low or flat angle slopes, measured thickness errors will be smaller - For low dips and low angle slopes, measured thickness errors will be larger (see figure 1) - With figure 1, it is obvious that you cannot measure the thickness of the strata by laying a ruler on the ground - The thickness of individual beds less than five feet thick can be easily measured with the Brunton (keeping in mind the dip) and a ruler or from a marked scale on the Jacob s Staff (for example - in one 5-foot interval, it is fairly easy to measure thicknesses by a variety of methods) - A stratigraphic section is always measured from the bottom up and 90 degrees from the strike (otherwise you have an apparent thickness - Measuring a dipping stratigraphic section using a Jacob s Staff General Method: - You must know the dip and strike of the strata before measuring its thickness (using a Jacob s Staff) 15

16 - #1. Set a dip angle on the clinometer that matches the strata dip - #2. Hold the Brunton securely on top of the Jacob s Staff - #3. The compass lid should be opened about 60 o, so that you can see the clinometer in the mirror and the sighting arm extended and its sight folded upwards (not easy to do) - #4. Place the bottom of the staff at the base of the rock unit to be measured and tilt the staff downwards (exactly perpendicular to strike) until you can see the (in the mirror) the clinometer bubble centered - #5. Find the next point on the ground by aligning the extended arm sight with the peep-hole line (on the mirror) - #6. Study the point sighted on the ground; place an object at that point (that will be the start of your next measurement). You have just measured five feet of stratigraphic section - #7. Normally here you would draw your stratigraphic column, describing the rocks in the unit. You can measure the thicknesses of the various beds by using either a ruler or the staff. - #8. Move the base of the staff to your new sighted point, and make your next measurements - #9. It is not uncommon to have to offset the line because of an obstacle to the next point - It will be rare instances if you can measure a section without perpendicular offsets, because of brush, dirt cover, a building, a cliff, a pit, etc., so be prepared to do as shown above - Practice using Brunton and Jacob staff method to measure stratigraphic thickness: - This measuring can be done on any campus lawn, especially with a building or set of bushes along the line of measurement so that you have to offset your measuring line - Students will work in pairs to measure a minimum of 50 feet thickness of dipping strata at predetermined angles of dip, following a predetermined strike, and the slope of the ground is flat. - EXAMPLE: measuring 50 feet of thickness of strata with a dip of 45 degrees, due West. - Because the slope of the ground is flat, with a dip of 45 degrees the distance to the point sighted: the ground length from the staff to the new point, can be measured for accuracy (the line is a hypotenuse of a 45 degree right angle or 5 feet times the square root of 2; what would the distance be for a 60 degree dip on a flat slope???) 16

17 - We will prepare a campus stratigraphic section like the one I have in the sketch below lll. Evaluation G: Grade the entries in students field book according to best practices Unit 5 Topic G Quiz 20 (tentative 20 points). Topic H: Determine the height of an object on level ground, using the Brunton Objective for Topic H: Utilize the clinometer on a Brunton to determine the height of an object Equipment and Location H: Pacing; Brunton, safety vests, tangent table in back of the field book (maybe on cell phone calculator application), calculator Introduction H: Geologists often need to be able to estimate the height of a feature in the field. They will use pacing and their Brunton clinometer angles to calculate the heights of various structures in the field. After a little practice, fairly accurate readings of heights can be calculated. (As a footnote, you can also use % grade to calculate heights. Learning Activities for Topic H: - Open the lid of the compass at 45 degrees, fold out sight arm with point a right angle and hold the Brunton at least a foot in front of you, with the mirror in your sight: - 1. Look through the window of the lid and tilt so that the top of the feature is lined up with your sights (see figure below) - 2. Move the clinometer level until you can see in the mirror that the bubble is centered Bring the compass down and record the readings - 4. Pace the distance from your point to the object and record the distance - 5. Multiply the distance paced times the tangent of the angle plus your height to get the feature height - In the back of your field book is a table of tangent values 17

18 Students will calculate the height of the Coles Bldg. and enter this in their field book. - The height can also be calculated with additional steps and by using the sine of the angle (which you can read about) - Also make mention of estimating height by using a pencil held at arm s length, in front of your face, and compared to a feature such as the known height such as a person. lll. Evaluation H: :Students will be graded by the relative accuracy of their readings and calculations with Unit 5 Topic H Quiz 21 (tentative 10 points) Topic I: Create a traverse round-trip map using a Brunton and pacing Objective for Topic I: Creating a simple round-trip traverse map on the DMC campus Equipment and Location I: Brunton, Pacing, safety vests, scales Introduction I: Geologists commonly have to make a traverse map when no other map is available during field studies, especially in canyons where the GPS is not functional. Learning Activities for Topic I: - Draw a ROUND-TRIP traverse map from and to Station #0 (via 6 other stations). - You are to: a. Take bearings using a Brunton (and cell phone if you have one) from station to station, entering the readings into your field book. b. ALSO BACK-SHOOT EACH BEARING AFTER YOU TRAVERSE TO THE POINT (always a good check) - If you have such an app, you can record your phone compass bearings as a check (AS YOU PROCEED) - Pace the distance between each station, entering the data into your field book - After collecting this data, (using an appropriate scale) draw a traverse map of this exercise. Use a protractor to draw the bearings and a scale for the distances. Be surprised if you get back exactly to zero. - Remember not to use the Brunton next to a steel pole or electrical boxes as these will severely affect your readings. - (See map on next page) 18

19 lll. Evaluation I: :Details and accuracy of their maps will be evaluated Unit 5 Topic I Map Quiz 22 (tentative 20 points) lv. Remediation: Repeat learning activities as needed 19