Transcript Geology of Maui

Geology of Island of Maui
•Island of Maui formed of two large shield volcanoes:
–West Maui Shield Volcano, ~ age 1.97 to 0.39 Ma,
Extinct Volcano
•has rocks from all three sub aerial eruptive phases:
shield, postshield alkalic cap, and rejuvenation
–East Maui Shield Volcano, 1.1 Ma to present,
Active Volcano
•has rocks from the late shield (rare) and postshield
alkalic cap (most of the volcano’s modern surface)
•is still in the postsheild alkalic cap stage
•includes Haleakala crater - an erosional feature
modified by later eruptions, Last erupted in 1790.
• Maui Nui -‘Greater Maui’ was geologically a very
large island, now spilt into four smaller islands.
• The four islands of Maui, Molokai Mo Mauiloka‘i,
Lana‘i, and Kaho‘olawe formed a single landmass in
the past called Maui Nui (Greater Maui) formed of 6
or 7 shield volcanoes. It included Penguin Bank,
now a submerged shelf between Molokai and Oahu.
• Around 2 million years ago, volcanoes on all of
these islands as well as the Ko‘olau on O‘ahu were
in their shield building stage, which means there
were 7 to 9 active shield volcanoes at the same time.
About 300,000 to 400,000 years ago, Maui Nui, which grew
from west to east. The Maui Nui subsided to form two islands,
one consisting of Penguin Bank, Moloka'i, and Lanai, and the
other consisting of Maui and Kaho'olawe. Kaho'olawe then
separated from Maui, and finally Lanai separated from
Moloka'i, both within the last 100,000 to 200,000 years.
Penguin Bank probably submerged within the last several
hundred thousand years.
During the last glacial maximum (LGM), about 21,000 years
ago, the Hawaiian Islands of Maui, Lanai, and Molokai were
interconnected by limestone bridges, creating a super-island
known as Maui-Nui. Approximately 120 m of sea-level rise
during the Holocene Transgression flooded, and then drowned,
these bridges separating the islands by inter-island
channels.With continued subsidence at the present-day rates,
East Maui (Haleakala) and West Maui will become separate
Hawaiian Islands
Oahu
Molokai
Maui
Lanai
Kaho‘olawe
Hawaii
Oahu
Hawaii
Splitting act of the Island of Maui Nui
Molokai
Maui
Lanai
Kaho‘olawe
Maui Nui probably had a maximum size of
about 11,000 square km (6,200 square miles),
some 4,000 square km (2,150 square miles)
larger than present-day Hawaii.
West Maui
Volcano and
Caldera
East Maui
Volcano
Haleakalā
Rift Zones
West Maui volcano, in
Rift Zones
the lower left, is 1800
meters high (5900 feet)
and is considered extinct.
East Maui volcano, rises
to an elevation of 3200
meters (10,500 feet).
Shield
East Maui Shield
Volcano Facts
Location Lat 20.7180
North Long 156.2540
West
Elevation Above Sea
Level
3,055 m, 10,023 ft
Area 1,470 km2 , 570
Radial
mi2
Drainage
(77% of Island of Maui)
Volume 30,000 km3
7,200 mi3 - 97% of
Haleakala Crater formed between 145,000
volume is below sea
and 120,000 years ago. It is a large erosional
valley at the summit of East Maui Volcano. level
Last erupted 1790
Island of Maui