Strike and dip symbols help geologists record characteristics of rock beds.
Geologic maps are a way for geologists to record various Earth structures such as fault lines, bedding planes and structural attitude. Two important geologic features recorded on geologic maps are strike and dip. Strike refers to the line on a rock bed that intersects with a hypothetical horizontal plane, and dip refers to the angle at which the rock bed is leaning verses that horizontal plane.
Instructions
1. Obtain a two-dimensional topographic map of the area. If one is not available, you will have to create one yourself by visiting the geographic area. A topographic map is an aerial view of the area that denotes elevation, rock type and any major fault lines or rock outcroppings. It is particularly important to pay attention to these faults as this is where most exposed rock will be for measuring strike and dip.
2. Locate a rock bed plane protruding upwards from the rest of the surface. Locate this rock on your map. Draw a small horizontal line on your map to represent a strike.
3. Place your compass, laying flat in your hand, at the same level as this line. Take note of where north is located. Face north. The strike line dimensions are denoted as the angles between which the line is running. For example, if you are facing north and the strike line is pointed in the same direction in which you are facing, the strike line is running zero degrees to 180 degrees or north to south. This is not usually written on a geologic map because the direction of your strike line on the map will provide this information.
4. Place a small tick mark on the strike line on your topographic map to indicate which way the rock bed is dipping. For example, if the strike like is running north to south, and your rock is dipping west, place a tick mark perpendicular to your strike line facing left (west).
5. Measure the dip of your rock bed. Using a protractor or your compass, if it has angles measured on it, place your instrument flush with the rock bed. Determine how many angular degrees the rock is sloping from a perfect horizontal flat imaginary line. Dips are always measured in acute angles, so make sure your measurement is less than 90 degrees.
6. Write the number of degrees next to the strike and dip symbol on your map without using a degree sign.
Tags: strike line, fault lines, geologists record, horizontal plane, line running, line your
