Assertion: cumulonimbus cloud's top | /r/MadeOf | ice crystals
Facets:
value: often
type: TEMPORAL
value: mostly
type: DEGREE
Source sentences:
text: The lower part is comprised of water droplets, while the wispy top is made of ice crystals that spread out as they reach the boundary below the stratosphere — a feature often referred to as the “anvil”.
text: These clouds are mostly made of water droplets, but the tops of very large cumulonimbus clouds are often made mostly of ice crystals.
text: If the rising air doesn't manage to cool down, it keeps rising all the way to the top of the troposphere and that forms towering cumulonimbus, the clouds that produce thunderstorms and where the anvil looking top is made of ice crystals.