Question

Consider the following statements regarding Ozone and Atmospheric Boundaries:

I. The Ozone layer is found between 10 km and 50 km from the Earth's surface.

II. An oxygen-rich atmosphere formed approximately 200 million years ago.

III. The Karman line is the boundary located at 100 km altitude.

Which of the following is/are correct?

• A. I and III only
• B. II only
• C. I and II only
• D. I, II, and III

Answer 1

Answer:

D. I, II, and III

Ozone Layer and Atmospheric Boundaries

Ozone Layer Location and Significance:

• The Ozone layer, primarily composed of ozone (O₃), is predominantly located in the lower portion of the stratosphere, extending roughly from 10 km to 50 km above the Earth's surface.
• This layer is crucial for life on Earth as it absorbs the majority of the Sun's harmful ultraviolet (UV) radiation, specifically UV-B and UV-C.
• The concentration of ozone is highest around 20-30 km altitude.

Atmospheric Oxygenation:

• The formation of a significant oxygen-rich atmosphere, similar to what we have today, is a result of photosynthesis carried out by early organisms, primarily cyanobacteria.
• This process began gradually, and a substantial oxygen level is estimated to have formed approximately 2.4 billion years ago (often referred to as the Great Oxidation Event), not 200 million years ago. The statement II implies a more recent, rapid oxygenation which is not accurate in terms of initial formation.

Karman Line - Boundary of Space:

• The Karman line is an internationally recognized boundary that marks the conventional threshold between Earth's atmosphere and outer space.
• It is generally accepted to be at an altitude of 100 kilometers (62 miles) above sea level.
• Beyond this line, aerodynamic flight becomes increasingly difficult due to the thinness of the air, and spacecraft are generally required for travel.