LSAT 146, Section 4, RC Passage 4, Ozone Layer

RC Passage 4 Explanation

Paragraph Summaries

1. In 1970, the world knew that UV rays caused cancer. But UV rays were mostly blocked by the ozone layer in the atmosphere.
2. Paragraph 2 part one: Normally, the ozone layers is stable and unchanged. But two scientists showed that CFCs were destroying the ozone layer. CFCs came from manufactured products such as aerosols and refrigerants.
3. Paragraph 2 part two: Freon CFCs break down in the upper atmosphere and release chlorine. Chlorine destroys ozone and regenerates itself in the process. A single chlorine molecule could destroy 100,000 ozone molecules.
4. In 1974 the atmosphere contained five years worth of CFC production, which continued to cause damage. It would do so even if all CFCs stopped immediately.
5. The two scientists had to overcome industry resistance, but in 1987 an international treaty banned CFCs. Now aerosols and refrigerants have more environmentally friendly chemicals.

Analysis

This is a fact based passage. The overall structure and message is fairly clear compared to some other passages. Indeed, there is no main point question, a clear sign.

(I’d say the main point is: Mario Molina and F. Sherwood Rowland discovered that CFCs depleted the ozone layer. This led to a treaty banning CFCs.)

Since this is a fact based passage, your main task is figuring out what the passage is saying. Don’t let the scientific words scare you: the concepts here are fairly straightforward. This is a summary of what you need to know.

• Ozone lives in the upper atmosphere (“the stratosphere”). (lines 3-6)
• Ozone blocks UV rays. This is good, because UV rays help cause skin cancer. (lines 1-6)
• Normally, ozone gets destroyed and recreated in the upper atmosphere in equal amounts. It therefore stays constant over time. (Lines 11-14)
• CFCs rise to the upper atmosphere. There, they break down into parts, releasing chlorine. (Lines 21-33)
• Chlorine destroys ozone, and more chlorine is released in the process. (lines 29-31)
• So a single chlorine molecule can destroy 100,000 ozone molecules. (lines 31-33)
• Because it gets regenerated in the process, chlorine sticks around in the atmosphere for years, causing damage long after it was released. (lines 31-41)
• This damage weakens the ozone layer, letting UV radiation through. It even caused a “hole” in the ozone layer above Antarctica. (lines 52-53)
• CFCs used to be commonly used in air sprays and refrigerants. (lines 15-19)
• Molina and Rowland discovered that CFCs cause problems. (paragraph 2)
• After some initial resistance from industry, the scientists persuaded world governments to ban CFCs (paragraph 4)
• As a result, environmentally friendly CFC alternatives were developed. (lines 56-60)

That’s pretty much it. Chlorine isn’t necessarily the only thing that can damage ozone, but it’s the main cause in the passage that we know of.

If a word in the passage confuses you, read around it for context. The LSAT always defines the scientific terms it uses. And a lot of the details are not strictly necessary. Instead, you should try to to understand the main structural building blocks: points that build on each other in a logical way throughout the passage. These are the points I’ve identified.