★Cause and Effect in Texts
Grade 5 Reading Worksheet
Circle the answer.
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The Hole in the Sky That Is Healing
High above the clouds, about 9 to 22 miles up, lies a thin layer of gas called ozone. You cannot see it or smell it, but it does an important job. The ozone layer soaks up most of the sun's ultraviolet, or UV, rays. Too much UV light can burn skin, harm eyes and damage plants. Without the ozone layer, life on Earth would be much harder.
In the 1980s, scientists made a worrying discovery. Each spring, the ozone layer above Antarctica was becoming dangerously thin. In some places, more than half of it was gone. People began calling this thin patch the ozone hole.
Scientists traced the problem to chemicals called CFCs. For decades, CFCs had been used in refrigerators, air conditioners and spray cans. They seemed perfect because they did not burn or react with other substances. However, that same stability meant they lasted a very long time in the air. Slowly, CFCs drifted upward until they reached the ozone layer.
Up there, strong sunlight broke the CFCs apart. This released chlorine, a gas that destroys ozone. A single chlorine particle can break down thousands of ozone particles. Because of this chain reaction, a small amount of CFCs caused a great deal of damage. The hole formed over Antarctica because the extremely cold clouds there speed up the process.
Once people understood the cause, they acted. In 1987, countries signed an agreement called the Montreal Protocol. They promised to stop making CFCs and other ozone-harming chemicals. Companies invented new ways to cool refrigerators and fill spray cans. Eventually, every country in the United Nations joined the agreement.
The results took time. Because CFCs last so long, the ones already in the air kept causing harm for years. But by the 2010s, scientists could measure the ozone hole shrinking. Today they expect the ozone layer over Antarctica to recover by about 2066.
The story of the ozone hole shows how one change can lead to another, and another. A useful chemical caused damage no one expected. Then careful science and teamwork began to reverse the harm. Many scientists call the Montreal Protocol one of the most successful environmental agreements in history.
What effect does the ozone layer have on sunlight reaching Earth?
- It turns the UV rays into clouds.
- It soaks up most of the UV rays.
- It lets more UV rays reach the ground.
- It makes the sunlight warmer.
What directly destroyed the ozone high in the air?
- UV rays that grew stronger each spring
- new cooling methods invented by companies
- chlorine released from broken CFCs
- spray cans that caught fire in the sky
Why were CFCs able to reach the ozone layer?
- Strong sunlight pulled them up from the ground.
- They lasted so long that they slowly drifted upward.
- They burned easily and rose into the sky like smoke.
- Companies sent them up to cool the air above Antarctica.
Why did a small amount of CFCs cause so much damage?
- Each CFC particle stayed in one spot for a hundred years.
- The ozone layer is only a few feet thick everywhere.
- CFCs were used in every single home on Earth for decades.
- One chlorine particle can break down thousands of ozone particles.
Why did the ozone hole form over Antarctica?
- Its extremely cold clouds speed up the damage.
- Antarctica gets no sunlight at any time.
- Most spray cans were used near Antarctica.
- The ozone layer there had always been thin.
What was one effect of the Montreal Protocol?
- CFCs began drifting up into the sky.
- The ozone layer recovered in one year.
- Companies found new ways to cool refrigerators.
- Scientists discovered the ozone hole.
