If the temperature reading at an observatory located on top of a dormant volcano is 6°C what will be the…

Analyze the question: Temperature falls as you go up through the troposphere. This is called the normal (environmental) lapse rate. We know the temperature at the top (6°C) and the height (3,000 m), and we need the temperature at the bottom.

Concept: The normal lapse rate is about 6.5°C per 1,000 m (some textbooks use 1°C per 150 m, which is about 6.7°C per 1,000 m). Going down, temperature increases by this rate.

Solution:

1. Temperature drop over 3,000 m: (6.5 ÷ 1,000) × 3,000 = 19.5°C

2. The bottom is lower, so it is warmer. Add this to the temperature at the top: 6°C + 19.5°C = 25.5°C

Check against the options:

• A (5.5°C) is wrong, because it would mean the bottom is colder.
• B (13.5°C) would need a drop of only 7.5°C, which is too small.
• C (25.5°C) matches our calculation.
• D (35.5°C) would need a drop of 29.5°C, which is too large.

Answer: C. 25.5°C

Exam tip: For lapse rate questions, remember "6.5 per 1,000." Going up means subtract, and going down means add. Always check the direction first. Since the question asks about the bottom, the answer must be warmer than 6°C, which immediately eliminates option A.