Maui Geology & Environment1.2 million year oldSecond largest island in the main chain727.3 square miles of land areaHighest elevation is 5,788 feetLargest perennial stream is 43 million gallons (`Iao Stream measures 163,000 cubic meters per day)

Haleakala crater volcano, East Maui Shield Volcanolast erupted in 1790

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).

Maui

Haleakala

East Maui Volcano

West Maui Volcano

Maui NuiThe four islands of Maui, Moloka`i, Lana`i, and Kaho`olawe were once all connected as a vast landmass known as Maui Nui, literally "big Maui." This concept was first proposed 60 years ago by geologist Harold Stearns, who recognized the geologic evidence for repeated episodes of island submergence and reemergence. Recently, Jonathan Price of the Smithsonian Institution modeled the area's submergence history using a computer-based geographic information system (GIS). The model examines the effects of global sea-level change, age of volcanism, and likely rates of volcano subsidence. Using Price's model, we can watch the response of Maui Nui to subsidence and sea-level change as we move the clock forward or back.

Haleakala Observatory

Haleakala

Maui Geology & EnvironmentSecond largest island in the main chain727.3 square miles of land areaHighest elevation is 5,788 feetLargest perennial stream is 43 million gallons (`Iao Stream measures 163,000 cubic meters per day)The long-term average water budget for east Maui was estimated for natural land-use conditions. The average rainfall, fog-drip, runoff, evapotranspiration, and ground-water recharge volumes for the east Maui study area are 2,246 Mgal/d, 323 Mgal/d, 771 Mgal/d, 735 Mgal/d, and 1,064 Mgal/d, respectively.