Geological Mapping Techniques

Geologists create two-dimensional flat maps to represent three-dimensional geological data.
Maps should provide comprehensive information for other geologists to visualize geology in the mapped area.
Field geologists observe landscapes, collecting data like rock types and their orientations.
Example: Stack of books symbolizes horizontal rock beds extending for kilometers.
Erosion results in various topographies (e.g., cliffs, hills) that must be understood separately from subsurface geology.
Topographic maps serve as the basis for recording geology.
"Attitude" refers to a bed’s orientation in three-dimensional space.

A horizontal bed is parallel to a flat surface; identifiable using a construction level.
Geologists use a Brundt and compass in the field to measure bedding attitudes.
On a map, horizontal beds are represented by a circle with a plus sign.
Horizontal beds show no visible contact on the surface unless eroded features expose underlying rock.
The contacts are at the same elevation, reflecting a concept called "layer cake stratigraphy."
When a bed is tilted, bedding contacts become visible on the surface.

To visualize bedding orientation, geologists need to document dip and strike.
Dip: Angle that a bedding plane makes with a horizontal plane; zero for horizontal beds.
- Measured typically using a protractor setup.
Strike: Line along the intersection of a bedding plane with a horizontal surface.
- Example for Strike: North 45° West indicated as direction of the strike line.
The direction of dip (downward) is crucial alongside dip angle and strike qualification.

Water flow direction can indicate bedding dip; it runs down perpendicular to the strike.
Example: A dip of 30° to the SW with strike of N 45° W is shown as a strike line with a dip tick mark.
For vertical beds, the dip is 90°, symbolized with two tick marks adjacent to the strike line; water flows straight down.
Geologists can recreate bed orientations using book models to practice aligning dip and strike.

Illustrates mapping 3 different attitude marks on maps.
For a strike approximately N 15° E with 60° dip NW: Align the strike and adjust the dip accordingly.
Vertical strike demonstrated (90°) requires the strike to be positioned accurately.
Horizontal beds have a zero dip, lacking a strike line due to parallel orientation to flat surfaces.

Measuring attitude when beds aren’t flat requires creating a parallel surface.
Tools such as levels and compasses are essential for establishing strike lines and measuring orientations.
Importance of measuring strike and dip: Indicates three-dimensional bedding orientation represented on two-dimensional maps, a core responsibility of field geologists.