---
title: "Strike of limestone bed dipping S55°E"
subject: "Engineering Geology I"
chapter: 5
key: "semester_3/engineering_geology_i:strike-of-limestone-bed-dipping"
source: https://www.bctengineer.com/q/semester_3/engineering_geology_i/strike-of-limestone-bed-dipping
site: BCT Engineering
---

# Strike of limestone bed dipping S55°E

Engineering Geology I · Chapter 5: Structural Geology

- Asked in: 2081 Chaitra (new course), 2 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-dipping
- Whole chapter: https://www.bctengineer.com/md/semester_3/engineering_geology_i/chapter-5

## Question

A limestone rock bed dips towards S55°E. Find its strike direction with a figure.

## Short answer

Dip direction is S55°E (azimuth 125°). Strike is always perpendicular to dip, so N35°E (azimuth 35°) or S35°W. Strike = N35°E (S35°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 bed dips towards S55°E. Dip direction = S55°E, azimuth = 125°.

$$
\begin{aligned} \text{Strike} &= \text{dip direction} \pm 90° \\ &= 125° - 90° = 35° \ \text{or}\ 125° + 90° = 215° \end{aligned}
$$

These two azimuths (35° and 215°) are the two ends of one line, so the strike is **N35°E (S35°W)**.
```text
              N
              |
              |   strike line (N35E)
              |  /
     W -------+-/------ E
              |/
              |  dip direction (S55E)
              S
```
**Answer: Strike = N35°E (S35°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 at 90° to the dip direction
   B. Strike is parallel to the dip direction
   C. Strike is at 45° to the dip direction
   D. Strike equals the dip amount
   Answer: A. 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 S55°E?
   A. 55°
   B. 125°
   C. 235°
   D. 145°
   Answer: B. Convert the quadrant bearing to an azimuth measured clockwise from north. (Key point: Azimuth conversion)

3. What is the strike for dip direction S55°E?
   A. N55°E (S55°W)
   B. N35°W (S35°E)
   C. N35°E (S35°W)
   D. N125°E
   Answer: C. Azimuth +/- 90° gives the two ends of one line, which is the strike. (Key point: Strike result)

## Related in Engineering Geology I

- [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×
- [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 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
- [Strike of limestone bed inclined east at 45°](https://www.bctengineer.com/question.md?key=semester_3%2Fengineering_geology_i%3Astrike-of-limestone-bed-inclined) — 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

## 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