---
title: "Strike of quartzite bed, dip 70° towards S20°E"
subject: "Engineering Geology I"
chapter: 5
key: "semester_3/engineering_geology_i:strike-of-quartzite-bed-dip"
source: https://www.bctengineer.com/q/semester_3/engineering_geology_i/strike-of-quartzite-bed-dip
site: BCT Engineering
---

# Strike of quartzite bed, dip 70° towards S20°E

Engineering Geology I · Chapter 5: Structural Geology

- Asked in: 2080 Bhadra, 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-quartzite-bed-dip
- Whole chapter: https://www.bctengineer.com/md/semester_3/engineering_geology_i/chapter-5

## Question

Define attitude of a rock. A quartzite bedrock dips at an angle 70° towards S20°E. Find out the strike of the bedrock with an illustration.

## Short answer

Attitude is the orientation of a rock layer defined by strike and dip. Given dip direction S20°E (azimuth 160°), strike is at 90° to it, giving N70°E (S70°W). Dip amount is 70°.

## Answer

#### Attitude of a rock
The **attitude** of a rock is its orientation in space, given by the **strike** (bearing of the horizontal line on the bed) and the **dip** (maximum inclination, with dip direction and dip amount). For lines, the attitude is given by trend and plunge.

#### Strike calculation
**Given**: dip amount = 70°, dip direction = S20°E, azimuth = $180° - 20° = 160°$.

$$
\text{Strike} = 160° - 90° = 70° \quad(\text{or } 160°+90° = 250°)
$$

So the strike is **N70°E** (the same line as S70°W).

```text
              N
              |
              |   strike line (N70E)
              |  /
     W -------+-/------ E
              |/
              |  dip direction (S20E)
              S
```

The dip amount (70°) does not change the strike; the strike depends only on the dip direction.

**Answer: Strike = N70°E; attitude = N70°E / 70° SE.**

## Check yourself

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

1. What does the attitude of a rock describe?
   A. Its mineral composition
   B. Its age only
   C. Its thickness only
   D. Its orientation in space: strike and dip (direction and amount)
   Answer: D. Attitude is strike plus dip. (Key point: Attitude)

2. 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)

3. What is the azimuth of the dip direction S20°E?
   A. 20°
   B. 200°
   C. 160°
   D. 110°
   Answer: C. Convert the quadrant bearing to an azimuth measured clockwise from north. (Key point: Azimuth conversion)

4. What is the strike for dip direction S20°E?
   A. N20°E (S20°W)
   B. N70°W (S70°E)
   C. N160°E
   D. N70°E (S70°W)
   Answer: D. Azimuth +/- 90° gives the two ends of one line, which is the strike. (Key point: Strike result)

5. Does the dip amount (70°) change the strike?
   A. Yes, strike = dip amount
   B. Yes, strike = 90° minus the dip amount
   C. No, strike depends only on the dip direction
   D. Yes, strike is halved
   Answer: C. The strike is fixed by dip direction; dip amount only gives steepness. (Key point: Role of dip amount)

## Related in Engineering Geology I

- [Strike of quartzite bed towards S20°W](https://www.bctengineer.com/question.md?key=semester_3%2Fengineering_geology_i%3Astrike-of-quartzite-bed-towards) — 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 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 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 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 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

## Related in other subjects

- [Reserve: quartzite apparent dips 1:9 and 1:12, 2.7 x 3.1 km](https://www.bctengineer.com/question.md?key=semester_4%2Fengineering_geology_ii%3Areserve-quartzite-apparent-dips-terrain) — Engineering Geology II, chapter 7, asked 2×
- [Reserve: quartzite apparent dips 1:9 and 1:12, 4.6 km2](https://www.bctengineer.com/question.md?key=semester_4%2Fengineering_geology_ii%3Areserve-quartzite-apparent-dips-area) — Engineering Geology II, chapter 7, asked 2×
- [Bedrock attitude: A 700 m N23E, C S71W](https://www.bctengineer.com/question.md?key=semester_4%2Fengineering_geology_ii%3Abh-hydropower-a700-n23e) — Engineering Geology II, chapter 6