Question

which example shows a positive feedback mechanism in earths systems?
ice cover increases, reflecting more sunlight and leading to cooler temperatures.
volcanic activity increases, releasing ash and causing cooling.
plants grow, reducing soil erosion and leading to more plant growth.
temperatures rise, melting polar ice and exposing darker surfaces that absorb more heat

Explanation:

A positive - feedback mechanism in Earth's systems amplifies the initial change. When temperatures rise, melting polar ice exposes darker surfaces that absorb more heat, which in turn causes more warming and more ice - melting, amplifying the initial temperature increase. In the other options, the changes lead to cooling or self - regulating effects which are negative feedback or not positive feedback.

Answer:

Temperatures rise, melting polar ice and exposing darker surfaces that absorb more heat.