Amorphous solid water is a non-crystalline form of water that can be made in the lab at very cold temperatures (a). Above a temperature of 140 K, the disorderly frozen molecules begin to form tiny crystalline grains of ice (b). When enough ice grains have formed, carbon tetrachloride (CCl₄) molecules, trapped under the amorphous water layer, can now escape by percolating up between the ice grains and emerge as a "molecular volcano" (c). (Illustration by Malcolm Tarlton, AIP.)