ASBOG - Association of State Boards of Geology Field Geology and Mapping Questions and Answers 2

Question 1

When measuring a planar feature's orientation in the field using a Brunton compass, what two measurements are recorded?

Accepted Answer

Strike and dip

Answer

Strike is the compass bearing of a horizontal line on the plane, and dip is the maximum angle of inclination measured from horizontal perpendicular to strike, together fully describing the plane's orientation.

Question 2

On a geologic map, what does a hachure pattern (short lines pointing downslope) on a contact indicate?

Accepted Answer

A thrust fault with the upper plate moving in the hachured direction

Answer

Hachures on a fault contact indicate a thrust or reverse fault, with the hachures pointing toward the overriding (hanging wall) block, indicating compression and upward movement.

Question 3

A geologist measures multiple joint orientations in a rock outcrop and plots them on a stereonet. What does a tight cluster of poles represent?

Accepted Answer

A consistent joint set with nearly uniform orientation

Answer

When poles to joints cluster tightly on a stereonet, it indicates a well-defined joint set where multiple joint surfaces have nearly the same strike and dip orientation.

Question 4

What is the purpose of a stratigraphic measured section in field geology?

Accepted Answer

To systematically document lithology, thickness, and vertical succession of rock units at a specific location

Answer

A measured stratigraphic section records the thickness, lithology, sedimentary structures, fossils, and vertical sequence of rock units in detail at one location to establish a reference column for correlation.

Question 5

When mapping in an area with poor outcrop, what remote sensing technique is most useful for identifying linear features that may represent faults or fractures?

Accepted Answer

Satellite-based synthetic aperture radar (SAR) or multispectral imagery

Answer

Satellite multispectral and SAR imagery reveals lineaments (topographic and drainage alignments) that may correspond to faults, joint zones, or lithologic contacts not visible in the field due to vegetation or soil cover.

ASBOG - Association of State Boards of Geology Practice Test

ASBOG - Association of State Boards of Geology Practice Test

ASBOG - Association of State Boards of Geology Field Geology and Mapping Questions and Answers 2