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Although it has been relatively placid in the recent past, Hualālai is still potentially active, and is expected to erupt again within the next 100 years.The USGS has divided the exposed lava flows and tephra erupted by Hualālai volcano during the last 112,000 years into 419 rock units of 8 chronostratigraphic age groups.Data collected showed that the lava flows there originated in shallow water 500 to 1,000 m (1,600 to 3,300 ft) deep, and that unlike similar slumps at other volcanoes, the slump at Hualālai formed gradually.Haulālai is a known source for xenoliths, rock from the Earth's mantle that have been brought up in lava flows.
The volcano is also important ecologically, is home to many rare species and several nature reserves near the summit, and is a popular hiking attraction.
Hualālai is estimated to have risen above sea level about 300,000 years ago.
Despite maintaining a very low level of activity since its last eruption in 1801, Hualālai is still considered active, and is expected to erupt again some time within the next century.
Trachyte flows move more slowly than the typically "runny" Hawaiian lavas, a characteristic caused by its high (over 62%) silica composition (typical basalt is only 50% silica).
Geologists hypothesize that Pua originally formed during a pumice eruption a little over 100,000 years ago, and has continued to build itself since then, with at least three distinct trachyte flows recognized.Although the two larger volcanos have each erupted over 150 times in the last 1,000 years, Hualālai has done so but 3 times.The recurrence of activity at the volcano seems to be every 200 to 300 years.Tholeiitic basalt, indicative of the submarine subphase of the volcano's construction, has been found in wells driven into the volcano at a depth of 75 ft (23 m).