---
title: "Dip direction from strike N55°E, dip 30°"
subject: "Engineering Geology I"
chapter: 5
key: "semester_3/engineering_geology_i:dip-direction-from-strike-n55e"
source: https://www.bctengineer.com/q/semester_3/engineering_geology_i/dip-direction-from-strike-n55e
site: BCT Engineering
---

# Dip direction from strike N55°E, dip 30°

Engineering Geology I · Chapter 5: Structural Geology

- Asked in: 2074 Chaitra, 4 marks
- Video: [TRUE DIP AND STRIKE DIRECTION NUMERICAL | geology ii | IOE | TU | EASY METHOD |](https://www.youtube.com/watch?v=6vDE-l2E4vQ) — Bishal Khadka
- Answer checked by Claude Opus 5.5 (high effort) on 2026-10-14
- Page: https://www.bctengineer.com/q/semester_3/engineering_geology_i/dip-direction-from-strike-n55e
- Whole chapter: https://www.bctengineer.com/md/semester_3/engineering_geology_i/chapter-5

## Question

Determine the dip direction of the bedding plane of a limestone bed which has strike N55°E and dip amount 30°.

## Short answer

Strike N55°E (55°). Dip direction can be S35°E (55°+90°) or N35°W (55°−90°). By the right‑hand rule, dip is to the southeast, so S35°E. Dip amount is30°.

## Answer

The dip direction is at 90° to the strike, so it is found by adding or subtracting 90° from the strike.

**Given**: strike = N55°E (azimuth 55°), dip amount = 30°.

$$
\begin{aligned} 55° + 90° &= 145° \ (\text{S}35°\text{E}) \\ 55° - 90° &= -35° = 325° \ (\text{N}35°\text{W}) \end{aligned}
$$

The strike alone does not say which side of it is lower, so the dip direction is **either S35°E or N35°W**; both are at 90° to the strike. In the field, the side is decided by seeing which way the bed slopes down (or from the geological map). If the bed dips towards the south-east side, the dip direction is S35°E. (By the right-hand-rule convention, where the dip is to the right of the quoted strike direction, N55°E gives S35°E.)

```text
                    N
      or N35W \     |     / N55E
                \   |   /
                  \ | /
  W ----------------+--------------------- E
                  / | \
                /   |   \
         S55W /     |     \ dip S35E
                    S
   ( / = strike line N55E-S55W,  \ = dip direction S35E, or N35W )
```

**Answer: Dip direction = S35°E (if dipping to the south-east) or N35°W (if dipping to the north-west); dip amount 30°.**

## Check yourself

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

1. How is the dip direction found from the strike?
   A. Add 45° to the strike
   B. Add or subtract 90° from the strike
   C. Equal to the strike
   D. Subtract the dip amount from the strike
   Answer: B. Dip direction is perpendicular to strike. (Key point: Method)

2. For strike N55°E, the two possible dip directions are
   A. S35°E and N35°W
   B. S55°E and N55°W
   C. N35°E and S35°W
   D. S55°W and N55°E
   Answer: A. 55+90 = 145° (S35°E); 55-90 = -35° = 325° (N35°W). (Key point: Candidates)

3. Why can the strike alone not give a single dip direction?
   A. Because dip amount is unknown
   B. Because strike is imprecise
   C. Because both sides always dip
   D. It does not say which side of the line is lower; this is decided in the field or on the map
   Answer: D. Strike is a line; either perpendicular direction is possible. (Key point: Choosing the side)

## Related in Engineering Geology I

- [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 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
- [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 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
- [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

## 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