Questions: What is a potential consequence of subsurface mining when the mines are abandoned?

The answer is the third one: subsidence and sinkholes.

Explanation for each option:

• Increased biodiversity: This is incorrect. Abandoned subsurface mines do not typically lead to increased biodiversity. In fact, they can disrupt local ecosystems and habitats, potentially reducing biodiversity.

• Increased agricultural productivity: This is incorrect. Abandoned mines can lead to soil contamination and land instability, which are detrimental to agricultural productivity rather than beneficial.

• Subsidence and sinkholes: This is correct. When mines are abandoned, the removal of underground materials can lead to the collapse of the ground above, causing subsidence and sinkholes. This is a well-documented consequence of subsurface mining.

• Decreased water pollution: This is incorrect. Abandoned mines can often lead to increased water pollution due to the leaching of harmful substances into groundwater and surface water, not a decrease in pollution.

In summary, the potential consequence of subsurface mining when the mines are abandoned is subsidence and sinkholes.