Adrian, who accepted being damaged by the disaster that he caused himself, is shocked by the golden mummy that he summoned. When Kanlaon used his fire and ice shields to protect them, Sirius also used his shadows as a shield to reinforce their defenses.
The sand disaster hit their defenses and it easily breached the first shield which is the fire shield. The fire shield managed to turn some of the sand into glass, but the force of the raging sands immediately shattered it within seconds.
The sands that managed to reach the frost shield melted due to the heat transferred. The sands might not be hot enough to melt the intense cold that the frost shield, but the constant collision of the shield and sands created friction. The friction made it possible for the frost shield to slowly melt and it slowly collapsed under the bombardment of the sands.