Which of the following disruptions would most likely cause an excess output of carbon into the atmosphere in the carbon cycle?

• A. Decreased volcanic activity
• B. Increased burning of fossil fuels
• C. Enhanced photosynthesis by phytoplankton
• D. Expansion of forested areas

Answer: (B)

Verified step by step guidance

1. Step 1: Understand the carbon cycle. The carbon cycle is the process by which carbon is exchanged among the atmosphere, biosphere, hydrosphere, and geosphere. Key processes include photosynthesis, respiration, decomposition, and combustion.
2. Step 2: Analyze the options provided. Each option represents a potential disruption to the carbon cycle. Consider how each would affect the balance of carbon in the atmosphere.
3. Step 3: Evaluate 'Decreased volcanic activity.' Volcanic activity releases carbon dioxide (CO₂) into the atmosphere. A decrease in volcanic activity would reduce CO₂ emissions, not cause an excess output of carbon.
4. Step 4: Evaluate 'Increased burning of fossil fuels.' Burning fossil fuels releases stored carbon in the form of CO₂ into the atmosphere, significantly increasing carbon output. This is a major contributor to excess atmospheric carbon.
5. Step 5: Evaluate 'Enhanced photosynthesis by phytoplankton' and 'Expansion of forested areas.' Both processes involve the absorption of CO₂ from the atmosphere during photosynthesis, which would reduce atmospheric carbon rather than increase it.