Stratospheric Ozone Depletion
Introduced| English | Meaning |
|---|---|
| ozone layer/ˈəʊzəʊn ˈleɪə/ | The region of the stratosphere with relatively high ozone concentration that absorbs much of the Sun's harmful ultraviolet radiation. |
| ultraviolet/ˌʊltrəˈvaɪəlɪt/ | Electromagnetic radiation with wavelengths shorter than visible violet light and longer than X-rays. |
| CFCs/ˌsiː ef ˈsiːz/ | chlorofluorocarbons: stable chlorine-containing gases once used in fridges and sprays that destroy stratospheric ozone |
| chlorine/ˈklɔːriːn/ | chlorine |
Earth's sunscreen
- High in the atmosphere sits the ozone layer 臭氧层.
- It absorbs most of the sun's harmful ultraviolet 紫外线 rays.
- Without it, that UV would damage life on the surface.
- In the 20th century, we accidentally started destroying it.
The culprit: CFCs
- CFCs 氯氟烃 were chemicals used in fridges and spray cans.
- They seemed safe — stable, cheap, and non-toxic.
- But when they leak, they drift slowly up into the atmosphere.
- It takes years for them to reach the ozone layer.
The ozone hole over Antarctica (dark blue) on a NASA satellite map: this is where the ozone layer has thinned the most
The ozone layer high in the atmosphere is important because it…
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The ozone layer absorbs most of the sun's harmful UV rays, shielding life below.
How they destroy ozone
- High up, the sun's UV breaks a CFC apart.
- This frees a chlorine 氯 atom.
- The chlorine atom rips apart ozone molecules.
- Worse, it keeps going — one atom destroys thousands.
How CFCs destroy the ozone layer
Follow a CFC from a spray can up to the stratosphere, where it destroys ozone.
Ozone depletion was caused mainly by CFCs, chemicals once used in…
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CFCs (chlorofluorocarbons) were used in cooling and sprays until they were found to destroy ozone.
A thinner ozone layer lets more harmful ____ radiation reach the ground.
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Less ozone means more UV reaches us, raising skin cancer and eye damage.
The ozone hole
- Over Antarctica, so much ozone was lost it became a "hole".
- A thinner layer lets more UV reach the ground.
- More UV means more skin cancer and eye damage.
- It also harms crops and the ocean's plankton.
A single chlorine atom can destroy many thousands of ozone molecules.
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Chlorine acts as a catalyst — it destroys ozone again and again without being used up.
Select all harms of a thinner ozone layer.
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More UV means more skin cancer, eye damage, and harm to crops and plankton. It does not help bones.
Don't confuse this with the greenhouse effect — they are different problems. Ozone depletion is about a thinning shield high up that lets harmful UV through (a radiation problem). The greenhouse effect is about gases trapping heat (a warming problem). A common exam trap is to mix them up. Also note: the ozone that shields us is high up (good); ground-level ozone in smog is a pollutant (bad).
The chlorine chain reaction:
- A CFC from an old fridge finally reaches the stratosphere after drifting up for years.
- The sun's UV splits it, freeing a chlorine atom.
- That one atom destroys an ozone molecule, then breaks free and destroys another, and another — thousands in all.
- Multiply by the billions of CFC molecules released, and the ozone layer thins into a hole.
The ozone layer shields Earth by absorbing the sun's harmful UV rays. CFCs from fridges and sprays drift up to the stratosphere, where UV frees a chlorine atom that destroys thousands of ozone molecules each. The thinning layer lets more UV through, causing skin cancer, eye damage, and harm to crops and plankton. (This is separate from the greenhouse effect.)