I believe the biosphere is fragile, because over time all of the pollution us humans have made; If its from air pulloution, acid rain or even water pollution. the toxic acids over time have made the biosphere and the ozon layer weaker and more thin. which causes the biosphere to become weaker.
It acts as a reactant in a chemical reaction.
A volcanic winter is a reduction in global temperatures caused by volcanic ash and droplets of sulfuric acid and water obscuring the Sun and raising Earth's albedo (increasing the reflection of solar radiation) after a large, particularly explosive volcanic eruption.
