This is a picture of a rare meteorological phenomenon called a skypunch (fallstreak hole) ice crystals form above the high altitude cirrocumulo stratus clouds, then fall downward, punching a hole in the cloud cover .. this picture shows a fallstreak hole against the background of the setting sun .. a fallstreak hole (also known as a hole punch cloud, punch hole cloud, skypunch, canal cloud or cloud hole) is a large circular or elliptical gap, that can appear in cirrocumulus or altocumulus clouds .. such holes are formed when the water temperature in the clouds is below freezing but the water has not frozen yet due to the lack of ice nucleation particles .. when ice crystals do form it will set off a domino effect, due to the bergeron process (ice crystal growth occurring in mixed phase clouds) causing the water droplets around the crystals to evaporate .. this leaves a large (often circular) hole in the cloud .. it is believed that the introduction of large numbers of tiny ice crystals into the cloud layer sets off this domino effect of evaporation which creates the hole .. the ice crystals can be formed by passing aircraft which often have a large reduction in pressure behind the wing or propeller .. this cools the air very quickly, and can produce a ribbon of ice crystals trailing in the aircraft's wake (contrails) .. these ice crystals find themselves surrounded by droplets and grow quickly, causing the droplets to evaporate and creating a hole with brush-like streaks of ice crystals below it..