Strike Direction and Dip Angle Measurement Planes

Understanding how geological features are oriented requires defining specific measurement planes:

• Strike Direction: This represents the trend (bearing) of a horizontal line lying on the surface of a planar geological feature (like a rock layer or fault). It is measured within the horizontal plane.
• Dip Angle: This is the angle at which the planar feature is inclined from the horizontal. It is measured downwards from the horizontal plane. The dip angle, along with the dip direction (the direction of steepest descent), is measured within a vertical plane that is perpendicular to the strike line.

Therefore, strike direction is measured in the horizontal plane, and the dip angle is measured in the vertical plane.

Referring to the options:

• Option A correctly identifies these planes as horizontal and vertical, respectively.