Which one of the following gases was not released through volcanoes around 4 billion years ago?

Correct option is C

The correct answer is (c) Oxygen. Oxygen was not released by volcanic activity around 4 billion years ago. During that period, volcanic emissions primarily included gases like hydrogen (H₂), nitrogen (N₂), carbon dioxide (CO₂), water vapor (H₂O), and methane (CH₄). Free molecular oxygen (O₂) was virtually absent because it did not exist in substantial amounts until the Great Oxidation Event, approximately 2.4 billion years ago, when photosynthetic cyanobacteria began to produce significant oxygen through photosynthesis.
Explanation of Other Options:
· (a) Hydrogen: Early volcanic activity released hydrogen gas due to the planet's molten state and chemical reactions with molten rock.
· (b) Nitrogen: Nitrogen gas was a significant component of volcanic emissions and contributed to the formation of Earth's early atmosphere.
· (d) Carbon dioxide: CO₂ was abundant in volcanic gases and played a major role in shaping the early atmosphere and climate.
Information Booster: 1. Great Oxidation Event: Oxygen levels increased significantly due to photosynthesis by cyanobacteria approximately 2.4 billion years ago.
2. Primordial Atmosphere: Composed primarily of hydrogen, water vapor, nitrogen, carbon dioxide, and methane.
3. Volcanic Gases: Early volcanic activity did not produce free oxygen. It emitted gases like H₂, CO₂, and N₂.
4. Oxygen Formation: Free oxygen accumulated later as a result of photosynthetic life.
5. Anoxic Earth: Before oxygen accumulation, Earth was largely anoxic (lacking oxygen), making the environment hostile to modern aerobic life.
6. Chemical Composition: Early Earth’s volcanic outgassing contributed to the formation of oceans and the first atmosphere.
Additional Knowledge: · Hydrogen: Released by volcanic activity and contributed to early chemical reactions that formed water.
· Nitrogen: Present in volcanic emissions and helped establish the nitrogen-rich atmosphere we have today.
· Oxygen: Appeared much later; initially, it quickly reacted with iron and other elements before accumulating in the atmosphere.
· Carbon Dioxide: A major volcanic emission; it played a critical role in early greenhouse warming.