Maui and Kahoolawe, Hawaii

Elevation: 1,476 feet (450 m) - Kahoolawe
10,023 feet (3,055 m) - Maui

The Island of Maui is made of two volcanoes: West Maui and East Maui. Most of the West Maui shield (20.9N, 156.6W) formed between 2-1.3 million years ago. A central caldera has been identified roughly in the area of the present-day Iao Valley. Alkalic basalts capped the volcano about 1.2 million years ago. Four small eruptions occurred during the rejuvenated stage on West Maui, probably about 1 million years ago. The volcano is deeply dissected by numerous valleys. West Maui has not erupted in historic time and is considered to be extinct.

East Maui Volcano, often also (but incorrectly) called Haleakala, is the easternmost of the two shield volcanoes that make the Island of Maui. East Maui Volcano (20.7N, 156.2W) is the third largest Hawaiian shield volcano. Three rift zones can be clearly seen in the above Space Shuttle photograph(compare with map below).

Most of the volcanic activity has been concentrated along the southwest and east rift zones. The impressive Haleakala Crater is at the summit of the volcano. Haleakala Crater is an erosional caldera, formed by the coalescence of the heads of two large valleys as they eroded into the volcano. The main shield of Haleakala is more than 800,000 years old. Lava flows and pyroclastics of the capping stage range in age from 930,000 to 350,000 years old. Rejuvenated-stage volcanic rocks occur along the rift zones and in the crater. The most recent eruption of Haleakala was in about 1790 at La Perouse Bay. Haleakala is considered an active volcano because this eruption is in historic time for Hawaii.
Kahoolawe (20.5N, 156.6W) is one of the smallest shield volcanoes in the Hawaiian Islands. Kahoolawe is the island near the bottom of the slide. The lava flows that make the main shield are 1-2 million years old. Wave erosion has exposed a caldera on the eastside of the island. Kahoolawe has not erupted in historic time and is considered to be extinct.

Source of information: Volcanoes of North America by Wood and Kienle.

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