page_title: Haleakalā
section_title: Geology
hierarchical_section_title: Haleakalā / Geology
caption_attribution_description: English: Looking northwest at Haleakala as seen from 85 kilometers/53 miles away on Big Island, Hawaii, near Kawaihae.jpg.
context_page_description: Haleakalā, 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, also referred to as the West Maui Mountains.
  The tallest peak of Haleakalā, at 10,023 feet, is Puʻu ʻUlaʻula. From the summit one looks down into a massive depression some 11.25 km across, 3.2 km wide, and nearly 800 m deep. The surrounding walls are steep and the interior mostly barren-looking with a scattering of volcanic cones.
context_section_description: According to the United States Geological Survey USGS Volcano Warning Scheme for the United States, the Volcano Alert Level for Haleakala as of August 2015 was "normal". A Normal status is used to designate typical volcanic activity in a non-eruptive phase.  Haleakala has produced numerous eruptions in the last 30,000 years, including in the last 500 years. This volcanic activity has been along two rift zones: the southwest and east. These two rift zones together form an arc that extends from La Perouse Bay on the southwest, through the Haleakalā Crater, and to Hāna to the east. The east rift zone continues under the ocean beyond the east coast of Maui as Haleakalā Ridge, making the combined rift zones one of the longest in the Hawaiian Islands chain.
  Until recently, East Maui Volcano was thought to have last erupted around 1790, based largely on comparisons of maps made during the voyages of La Perouse and George Vancouver.  Recent advanced dating tests, however, have shown that the last eruption was more likely to have been in the 17th century.  These last flows from the southwest rift zone of Haleakalā make up the large lava deposits of the Ahihi Kina`u/La Perouse Bay area of South Maui.
  Contrary to popular belief, Haleakalā crater is not volcanic in origin, nor can it accurately be called a caldera (which is formed when the summit of a volcano collapses to form a depression). Scientists believe that Haleakalā's crater was formed when the headwalls of two large erosional valleys merged at the summit of the volcano. These valleys formed the two large gaps — Koʻolau on the north side and Kaupō on the south — on either side of the depression.
  Macdonald, Abbott, & Peterson state it this way:
  Haleakalā is far smaller than many volcanic craters (calderas); there is an excellent chance that it is not extinct, but only dormant; and strictly speaking it is not of volcanic origin, beyond the fact that it exists in a volcanic mountain.
caption: Haleakala as seen looking northwest from Big Island, Hawaii, near Kawaihae, 85 kilometers (53 mi) away
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