Why does ice crack when a drink is poured on it?
I believe the ice cracked due to residual strains from freezing. Since ice freezes from the outside inward and it expands as it freezes, that as the inner water freezes, it imparts a tensile force on the surrounding ice (like the opposite effect of tempering glass).  As the warm liquid removes ice, the cross sectional area under tension decreases while the tensile force remains the same, causing an increase in stress. Once the stress reaches a certain point, the ice fails to counter the tension mechanically, causing the cracks.