Haleakalā (/ˌhɑːliːˌɑːkəˈlɑː/; Hawaiian: [ˈhɐleˈjɐkəˈlaː]), or the East Maui Volcano, is a massive shield volcano that forms more than 75% of the Hawaiian Island of Maui. The western 25% of the island is formed by another volcano, Mauna Kahalawai, which according to volcanologists, used to be over 13,000 feet high, but has collapsed and eroded down to a much smaller 5,100 feet. Mauna Kahalawai is the older of the two volcanoes at 1.4 million years old and Haleakala is 1.2 million years old. Mauna Kahalawai, because of all the erosion giving it the look of many mountains, is referred to as the West Maui Mountains.
According to legend, in the awe-inspiring basin at Haleakalā’s summit, the demigod Maui snared the sun, releasing it only after it promised to move more slowly across the sky. Haleakalā means "house of the sun"; the Haleakalā National Park encompasses the basin and portions of the volcano's flanks.
A United Nations International Biosphere Reserve, the park comprises starkly contrasting worlds of mountain and coast. The road to the summit of Haleakalā rises from near sea level to 10,023 feet in 38 miles—possibly the steepest such gradient for autos in the world. Visitors ascend through several climate and vegetation zones, from humid subtropical lowlands to subalpine desert. Striking plants and animals such as the Haleakalā silversword (blooming ahinahina plant) and the nēnē (Hawaiian Goose) may be seen in this mountain section.
The summit-area depression formed as erosion ate away the mountain, joining two valleys. This 19-square-mile wilderness area, 2,720 feet deep, is the park's major draw….Manhattan Island would fit in here.