---
title: "Strike of limestone bedrock dipping N31°W"
subject: "Engineering Geology I"
chapter: 5
key: "semester_3/engineering_geology_i:strike-of-limestone-bedrock-dipping"
source: https://www.bctengineer.com/q/semester_3/engineering_geology_i/strike-of-limestone-bedrock-dipping
site: BCT Engineering
---

# Strike of limestone bedrock dipping N31°W

Engineering Geology I · Chapter 5: Structural Geology

- Asked in: 2068 Baisakh, 4 marks
- Answer checked by Claude Opus 5.5 (high effort) on 2026-10-14
- Page: https://www.bctengineer.com/q/semester_3/engineering_geology_i/strike-of-limestone-bedrock-dipping
- Whole chapter: https://www.bctengineer.com/md/semester_3/engineering_geology_i/chapter-5

## Question

Determine the strike direction of the bedding plane of limestone bedrock, which dips towards N31°W.

## Short answer

Strike is perpendicular to dip direction. For a dip of N31°W, the strike is N59°E (S59°W).

## Answer

The strike is the direction of the horizontal line on the bed and it is always at 90° to the dip direction.

**Given**: Limestone bedrock dips towards N31°W. Dip direction = N31°W, azimuth = 329°.

$$
\begin{aligned} \text{Strike} &= \text{dip direction} \pm 90° \\ &= 329° - 90° = 239° \ \text{or}\ 329° + 90° = 59° \end{aligned}
$$

These two azimuths (59° and 239°) are the two ends of one line, so the strike is **N59°E (S59°W)**.

```text
                    N
     dip N31W \     |     / N59E
                \   |   /
                  \ | /
  W ----------------+--------------------- E
                  / |
                /   |
         S59W /     |
                    S
   ( / = strike line N59E-S59W,  \ = dip direction N31W, at 90 deg to strike )
```

**Answer: Strike = N59°E (S59°W).**

## Check yourself

The answer's key points as multiple-choice questions, with the correct option and why.

1. How is strike related to the dip direction?
   A. Strike is parallel to the dip direction
   B. Strike is at 90° to the dip direction
   C. Strike is at 45° to the dip direction
   D. Strike equals the dip amount
   Answer: B. Strike is the horizontal line on the bed, perpendicular to dip direction. (Key point: Strike vs dip direction)

2. What is the azimuth of the dip direction N31°W?
   A. 31°
   B. 149°
   C. 329°
   D. 211°
   Answer: C. Convert the quadrant bearing to an azimuth measured clockwise from north. (Key point: Azimuth conversion)

3. What is the strike for dip direction N31°W?
   A. N31°E (S31°W)
   B. N59°W (S59°E)
   C. N31°W (S31°E)
   D. N59°E (S59°W)
   Answer: D. Azimuth +/- 90° gives the two ends of one line, which is the strike. (Key point: Strike result)

## Related in Engineering Geology I

- [Strike of limestone bed dipping S55°E](https://www.bctengineer.com/question.md?key=semester_3%2Fengineering_geology_i%3Astrike-of-limestone-bed-dipping) — Engineering Geology I, chapter 5
- [Strike of limestone bed, dip N40°W, 64°](https://www.bctengineer.com/question.md?key=semester_3%2Fengineering_geology_i%3Astrike-of-limestone-bed-dip) — Engineering Geology I, chapter 5
- [Strike of quartzite bed, dip 70° towards S20°E](https://www.bctengineer.com/question.md?key=semester_3%2Fengineering_geology_i%3Astrike-of-quartzite-bed-dip) — Engineering Geology I, chapter 5
- [Strike of quartzite bed, dip 80° towards N10°E](https://www.bctengineer.com/question.md?key=semester_3%2Fengineering_geology_i%3Astrike-of-quartzite-bed-dip-80) — Engineering Geology I, chapter 5
- [Dip direction from strike N55°E, dip 30°](https://www.bctengineer.com/question.md?key=semester_3%2Fengineering_geology_i%3Adip-direction-from-strike-n55e) — Engineering Geology I, chapter 5
- [Strike of quartzite bed dipping S25°E](https://www.bctengineer.com/question.md?key=semester_3%2Fengineering_geology_i%3Astrike-of-quartzite-bed-dipping) — Engineering Geology I, chapter 5, asked 2×

## Related in other subjects

- [Limestone true thickness across stream](https://www.bctengineer.com/question.md?key=semester_4%2Fengineering_geology_ii%3Astream-limestone-true-thickness) — Engineering Geology II, chapter 6