Question

Ozone hole refers to: (a) Hole in ozone layer (b) Reduction in the thickness of ozone layer in stratosphere (c) Reduction in the thickness of ozone layer in troposphere (d) Increased concentration of ozone

Short answer

The ozone hole refers to a reduction in the thickness of the ozone layer in the stratosphere, so the answer is (b).

Step-by-step solution

Identifying the Context

The exercise is about understanding the term 'ozone hole'. This term often appears in environmental science topics and is important to differentiate where changes in the ozone layer occur.

Understanding Ozone Layer Importance

Ozone is a molecule comprised of three oxygen atoms. The ozone layer absorbs most of the Sun's harmful ultraviolet radiation, preventing it from reaching the surface of the Earth.

Locating the Ozone Layer

The ozone layer primarily resides in the stratosphere, one of the layers of Earth's atmosphere, located about 10 to 50 kilometers above Earth's surface.

Defining the Ozone Hole

The term 'ozone hole' refers to the phenomenon where there is a significant reduction in the concentration of ozone in the stratosphere. Specifically, it is about the thinning of this layer rather than a literal hole or changes in the troposphere.

Analyzing the Options

- Option (a) describes a literal 'hole', which is not what 'ozone hole' signifies. - Option (c) is incorrect because the troposphere isn't where the ozone layer primarily resides. - Option (d) suggests an increase in ozone, which contradicts the notion of a hole or thinning. - Option (b) precisely describes the reduction in the thickness of the ozone layer in the stratosphere.

Selecting the Correct Answer

Based on the analysis, the correct understanding of 'ozone hole' aligns with option (b).

Key concepts

Stratosphere: A Layer Above

The stratosphere is a layer of Earth's atmosphere, located above the troposphere and below the mesosphere. It sits approximately 10 to 50 kilometers (about 6 to 31 miles) above the Earth’s surface. A defining feature of the stratosphere is its temperature profile, which increases with height due to the absorption of ultraviolet (UV) radiation by the ozone layer.
The absorption of UV radiation not only warms this layer but also plays a crucial role in protecting life on Earth from the Sun’s harmful rays.

• Most commercial jet airplanes fly in the lower stratosphere, as it is usually free of clouds and turbulence, providing a smoother ride.
• The air in the stratosphere is also much drier and holds less water vapor than the troposphere, contributing to weather stability.

The thickness and stability of the stratosphere make it an ideal location for the bulk of the ozone layer, reinforcing its critical function in shielding biological entities from excessive ultraviolet exposure.

Ultraviolet Radiation and Its Effects

Ultraviolet (UV) radiation is a type of electromagnetic radiation coming from the Sun. It is invisible to the human eye and can have serious effects on living organisms. UV radiation is divided into three types: UVA, UVB, and UVC. Each type varies in wavelength and biological impact.

• UVA: Has the longest wavelength, can penetrate deep into the skin, leading to premature aging. It contributes less to DNA damage compared to UVB.
• UVB: Has a medium wavelength and is mainly responsible for sunburn. It plays the largest role in causing skin cancer as it affects the DNA directly.
• UVC: Has the shortest wavelength and is absorbed by the ozone layer, preventing it from reaching us at the Earth's surface.

The presence of the ozone layer in the stratosphere is crucial for filtering out the most harmful UV radiation, particularly UVB and UVC. Without this protective shield, life on Earth would be exposed to increased risks of skin cancer, cataracts, and damage to ecosystems.

The Intersection of Environmental Science and the Ozone Layer

Environmental science is the study of how natural and artificial processes interact within the environment. The ozone layer has become a critical focal point within this field due to its vital role in sustaining life.
In the 20th century, human-made chemicals, such as chlorofluorocarbons (CFCs), were found to deplete the ozone layer. CFCs, once used widely in refrigeration and aerosol cans, release chlorine atoms when broken down by UV light, which then leads to ozone destruction in the stratosphere.

• The detection of the 'ozone hole' over Antarctica in the late 1970s highlighted the impact of these chemicals.
• This discovery led to international environmental policy actions such as the Montreal Protocol in 1987, aimed at phasing out CFCs and other ozone-depleting substances.

Efforts in environmental science continue to focus on monitoring the health of the ozone layer, with current data suggesting it is slowly recovering, thanks to global cooperation and policy enforcement.