Mauna kea means “white mountain” in the Hawaiian language, a reference to its summit being regularly covered by snow in winter. The peak of Mauna Kea is 4,207 m above sea level but 10,203 m above its base on the floor of the Pacific Ocean. It is the world’s tallest mountain by this measure, taller than Mount Everest, which is the highest mountain above sea level.
Mauna Kea is in the post-shield stage of volcanic evolution, having made the transition from the shield stage about 200,000 to 250,000 years ago. At that time, its appearance was probably quite similar to that of its neighbor Mauna Loa today, a smooth shield volcano with a large summit caldera. Following the transition, eruptions became more explosive in character, resulting in the formation of numerous overlapping cinder cones which eventually filled and completely obscured the caldera. These cinder cones now form the peaks at the summit of Mauna Kea, with several of them exceeding 13,500 feet (4,100 m) in elevation. After several hundred thousand years of slowly building itself up by volcanic activity, the mountain’s height is slowly decreasing now as its massive weight depresses the Pacific seafloor beneath it.
Snowfall often occurs at elevations above 3,400 m during the period from November through March. During particularly cold and wet winters, which are usually linked to La Niña, a snowpack several feet (1 m) deep may remain in the summit region above 4,000 m for weeks or months. This permits skiing and other snow-play activities on the slopes of the cinder cones.
The summit of Mauna Kea has been a celestial observatory since ancient times and is considered to be one of the best astronomical sites in the world. For this reason it is home to many of the world’s leading astronomical observatories. The summit is above approximately 40% of Earth’s atmosphere and 90% of the water vapor, allowing for exceptionally clear images of the night sky. Additionally, the peak is well above the inversion layer, which leads to approximately 300 clear nights per year. (Source: Wikipedia)
The thing that fascinated me the most was that you can go swimming in the Pacific and about 2 hours later you are standing on top of Mauna Kea about 4207 m higher with temperatures well below freezing and yea if you have brought your skis along you could go skiing.