---
title: "Strike of limestone bed, dip N40°W, 64°"
subject: "Engineering Geology I"
chapter: 5
key: "semester_3/engineering_geology_i:strike-of-limestone-bed-dip"
source: https://www.bctengineer.com/q/semester_3/engineering_geology_i/strike-of-limestone-bed-dip
site: BCT Engineering
---

# Strike of limestone bed, dip N40°W, 64°

Engineering Geology I · Chapter 5: Structural Geology

- Asked in: 2076 Asoj, 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-bed-dip
- Whole chapter: https://www.bctengineer.com/md/semester_3/engineering_geology_i/chapter-5

## Question

Determine the strike of the bedding plane of limestone bedrock, which has dip direction N40°W and dip amount 64°.

## Short answer

Dip direction N40°W (azimuth 320°). Strike = 320° − 90° = 50° (N50°E) and 320° + 90° = 230° (S50°W). Strike is N50°E (S50°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 bedding plane, dip direction N40°W, dip amount 64°. Dip direction = N40°W, azimuth = 320°.

$$
\begin{aligned} \text{Strike} &= \text{dip direction} \pm 90° \\ &= 320° - 90° = 230° \ \text{or}\ 320° + 90° = 50° \end{aligned}
$$

These two azimuths (50° and 230°) are the two ends of one line, so the strike is **N50°E (S50°W)**.

```text
                    N
     dip N40W \     |     / N50E
                \   |   /
                  \ | /
  W ----------------+--------------------- E
                  / |
                /   |
         S50W /     |
                    S
   ( / = strike line N50E-S50W,  \ = dip direction N40W, at 90 deg to strike )
```

**Answer: Strike = N50°E (S50°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 45° to the dip direction
   C. Strike is at 90° to the dip direction
   D. Strike equals the dip amount
   Answer: C. 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 N40°W?
   A. 40°
   B. 140°
   C. 220°
   D. 320°
   Answer: D. Convert the quadrant bearing to an azimuth measured clockwise from north. (Key point: Azimuth conversion)

3. What is the strike for dip direction N40°W?
   A. N50°E (S50°W)
   B. N40°E (S40°W)
   C. N50°W (S50°E)
   D. N40°W (S40°E)
   Answer: A. Azimuth +/- 90° gives the two ends of one line, which is the strike. (Key point: Strike result)

## Related in Engineering Geology I

- [Strike when dip direction is N40°W](https://www.bctengineer.com/question.md?key=semester_3%2Fengineering_geology_i%3Astrike-when-dip-direction-is) — 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 limestone bedrock dipping N31°W](https://www.bctengineer.com/question.md?key=semester_3%2Fengineering_geology_i%3Astrike-of-limestone-bedrock-dipping) — Engineering Geology I, chapter 5
- [Strike of limestone bed directed N20°E, dip 45°](https://www.bctengineer.com/question.md?key=semester_3%2Fengineering_geology_i%3Astrike-of-limestone-bed-directed) — Engineering Geology I, chapter 5
- [Dip amount, strike; fold identification criteria](https://www.bctengineer.com/question.md?key=semester_3%2Fengineering_geology_i%3Adip-amount-strike-fold-identification) — Engineering Geology I, chapter 5
- [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

## Related in other subjects

- [Reserve: limestone dip 30, apparent 20 m](https://www.bctengineer.com/question.md?key=semester_4%2Fengineering_geology_ii%3Areserve-limestone-dip-30) — Engineering Geology II, chapter 7