Which of earth's mechanical layers is most easily deformed?

Aletsch glacier is the largest glacier in switzerland and the largest found in the alps, a mountain range which extends from monaco in the east to slovenia in the west. currently, the aletsch glacier is retreating. under what circumstances would this glacier see growth instead of retreat? a decline in plate tectonics across the mountain range annual snowfall that exceeds yearly losses an increase in ablation in the southern valleys a rise in temperatures to that of a mediterranean climate