What type of cloud is typical of very high altitudes and thin appearance?

The type of cloud that is typical of very high altitudes and has a thin appearance is indeed the cirro cloud. Cirrus clouds, which fall into this category, generally form at altitudes above 20,000 feet (6,000 meters) and are characterized by their wispy and delicate appearance. This is due to the fact that they consist primarily of ice crystals rather than liquid water, as the temperatures at such high elevations are often above freezing.

Cirrus clouds can indicate that a change in weather may be on the way, as they often precede a warm front, leading to more dynamic weather patterns. Their appearance is usually a sign of fair weather, but they can also indicate that upper-level moisture is present, which may lead to the development of other types of clouds or precipitation as atmospheric conditions evolve.

In contrast, stratus clouds are low and often blanket the sky, alto clouds occupy a mid-level altitude, and cumulonimbus clouds are towering and associated with thunderstorms. These cloud types do not fit the description of being high-altitude and thin like cirrus clouds.