Mauna Kea on the Big Island of Hawai'i
with a light dusting of snow. Viewed from Hualalai Mountain
Mauna Kea is an inactive, probably extinct, volcano in the Hawaiian Islands, one of five volcanic peaks that together form the Island of Hawaii. In Hawaiian mauna kea means "white mountain", a reference to the fact that it is regularly snow or frost capped in the northern hemisphere winter. The top of the mountain peaks out at 13,976 ft (4,205 m) on Pu'u Wekiu (one of numerous cinder cones on the summit), the highest point in the Hawaiian Islands.

The elevation and location of Mauna Kea have made it an important location for atmospheric and astronomical observations. The summit is above approximately 40% of Earth's atmosphere and 90% of the water vapor, allowing for clearer images. Additionally, the peak is above the inversion layer, allowing up to 300 clear nights per year. Also, at 20°N latitude, much of the southern sky is visible. The summit is widely known for its observatories built by many nations, the best seeing disk with a measurement of ~0.2 arcseconds.

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