31.9k views
3 votes
What is strike and dip and how are they plotted on a map?

User Blobbie
by
7.3k points

1 Answer

2 votes

Final answer:

Strike is a horizontal intersection direction of a rock layer, and dip is the layer's tilt angle. They are measured with a Brunton Compass and plotted on geologic maps using symbols.

Step-by-step explanation:

Strike and dip are geological terms used to describe the orientation of rock layers. A strike is the direction of the line formed by the intersection of a rock layer with the horizontal surface, while a dip is the angle at which the rock layer is tilted from the horizontal.

On a geologic map, strike and dip are plotted using symbols: a long line indicates the strike direction and a short line perpendicular to the strike line shows the dip direction, with the number representing the angle of dip.

Geologists use a Brunton Compass to measure these orientations accurately. When plotting these measurements, the strike is written first, followed by the dip angle and direction.

For example, 040/30 SE would indicate a strike of 40 degrees and a dip of 30 degrees to the southeast. The right-hand rule is commonly applied to ensure that the strike is perpendicular to the dip direction.

It is crucial for geologic maps to also include a scale and a north arrow. When creating a cross-section, aligning it perpendicular to the strike of the layers will display the true dip. If the cross-section isn't perpendicular, it will show an apparent dip, which is smaller than the true dip.

User Giorgos Altanis
by
8.6k points
Welcome to QAmmunity.org, where you can ask questions and receive answers from other members of our community.

9.4m questions

12.2m answers

Categories