Which statement about strike direction in the United States is true?

• A. SE or SW
• B. N or S
• C. E or W
• D. NE or NW

Answer: (D)

Strike direction is the compass direction of the line formed by the intersection of a rock layer with a horizontal plane. In the United States, the regional structural patterns created by long geologic histories tend to align features along northeast–southwest trends. Because of that, the lines along which beds and faults commonly run point toward the northeast or the northwest, i.e., NE or NW. The other directions describe lines that are either strictly cardinal (N/S or E/W) or run along different orientations (SE/SW) that are less representative of the country’s broad bedded-rock fabric.