LSAT 151 | Section 2 | Logical Reasoning: Q16

LR Question 16 Explanation

QUESTION TEXT: Scientist: An orbiting spacecraft detected a short-term spike …

QUESTION TYPE: Weaken

CONCLUSION: We shouldn’t conclude that volcanic activity caused the sulfur dioxide spike.

REASONING: No active volcanoes have been identified on Venus, and planetary atmospheres can naturally go through chemical cycles.

ANALYSIS: The structure here is:

• Sulfur dioxide spikes can be caused by volcanoes (on Earth)
• Venus has signs of past volcanic activity
• BUT don’t conclude volcanoes caused this spike because:
• no active volcanoes have been identified
• there are other possible explanations (atmospheric cycles)

So to weaken this, you want to make the volcanic explanation look more plausible.

The biggest thing you can probably poke holes in is “no active volcanoes have been identified.” Us not being able to find something doesn’t mean it’s not there. It could just be really hard to identify it.

___________

1. CORRECT. Right. If conditions on Venus make it hard/impossible to detect eruptions, then the fact that we haven’t identified any active volcanoes is much less persuasive. They could absolutely exist. We just might not be able to see them.
2. Okay, so this has happened before. But this doesn’t tell us what caused either spike. If anything, the scientist could just say that this supports the idea of recurring cycles.
3. We care about spikes within Venus. Comparisons to Earth tell us nothing relevant.
4. This tells us volcanic sulfur dioxide can linger for years, but there’s still an unexplained short-term spike.
5. This is silly. No one’s burning fossil fuels on Venus. How does this help with anything?