Hualālai

Name	Hualālai
Photo	Hualālai 1996.jpg
Photo caption	View of Hualālai over 1800 lava flow
Elevation ft	8,271
Elevation ref

Hualālai (pronounced in Hawaiian) is a dormant shield volcano on the island of Hawai i in the Hawaiian Islands. It is the third-youngest and the third most active of the five volcanoes that form the island of Hawai i, following the much larger Kīlauea and Mauna Loa, and also the westernmost. Its peak is above sea level.

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. The relative unpreparedness of the residents in the area caused by the lull in activity would worsen the consequences of such an event.

The volcano has been inhabited for centuries by Hawaiian natives, dating back to before recorded history. The coast west of Hualālai in particular had several royal complexes. 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. Today the coast near Hualālai is pocketed by multiple vacation resorts, some built on historic flows, and a National historic park.

Geology

Structural features

Hualālai stands at with a prominence of . It is the westernmost of the five major volcanoes which form the island of Hawai i. Being in the post-shield stage of development, Hualālai is overall much rougher in shape and structure than the more youthful Mauna Loa and Kīlauea. Hualālai's structure is denoted by three rift zones: a well-developed one approximately 50° to the northwest, a moderately developed one to the southeast, and a poorly developed one trending northwards about east of the summit. There are over 100 cinder and splatter cones arranged along these rift zones. Hualālai has no summit caldera, although there is a collapse crater about across atop a small lava shield. Much of the southern slope (above the modern town of Kailua-Kona) consists of lava flows covered by a layer of volcanic ash from thick. In comparison with the other volcanoes of the island of Hawai i, it is the third tallest, third oldest, third most active, and second smallest, making up just 7% of the island.

Haulālai is a known source for xenoliths, rock from the Earth's mantle that have been brought up in lava flows. Many prehistoric deposits, as well as those from the 1801 event, contain xenoliths of large size and abundant quantity. Hualālai entered the post-shield stage, the stage it is presently in, about 100,000 years ago. Pumice and trachyte eruptions at Pu u Wa awa a may be a sign of this change.

Geological mapping of the volcano has indicated that as much as 80% of the volcano's surface has been topped by lava flows during the last 5,000 years,

A recent calm period, with almost no earthquake or magmatic activity at Hualālai, has seen the growth of homes, businesses, and resorts on the mountain's flanks. The most recent major activity at the volcano was in 1929, when an intense earthquake swarm rocked Hualālai, most likely caused by magmatic action near the volcano's peak. 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. |- !Age Group!!Age (years before present)!!Rock type!!Surface area (percent)!!Number of rock units!!Location of exposures!!Comments |- |8 |less than 200 |alkali basalt |6 |3 |northwest flank |Vent cinder deposits with black pahoehoe basalt lava flows formed during AD 1800–1801 eruption. Five vents along NW rift zone. Abundant xenoliths of ultramafic plutonic rocks. |- |7 |200–700 |alkali basalt |3 |4 |southern flank |Vent lava spatter and lava flows, cinders and tuff at Waha Pele. Spatter cone erupted pahoehoe and ʻAʻā basalt lava flows. Cone collapsed causing violent phreatic eruptions of tuff. Lava flow eruption resumed building larger cone, with eruption of long ʻAʻā lava flows. |- |6 |750-1,500 |alkali basalt |8 |14 |mostly central summit area and southeast flank |Dark grey to black vent lava spatter (including a 650 metre long spatter rampart), cinders, aa and pahoehoe basalt lava flows, including Hualalai's longest lava flow (22 km). Collapse of vents produced pit craters. Hawaiian, Strombolian and sub-Plinian activity. |- |5 |1,500–3,000 |alkali basalt |38 |49 |mostly northern flank |Spatter deposits, ʻAʻā and pahoehoe basalt lava flows. Very active 2,400–1,900 years before present. |- |4 |3,000–5,000 |alkali basalt |25 |98 |mostly northern flank and summit |Spatter deposits, aa and pahoehoe basalt lava flows. |- |3 |5,000–10,000 |alkali basalt with minor amounts of picritic basalt, hawaiite and ankaramite |15 |185 |mostly southern flank and summit |Spatter deposits, extensively weathered aa and pahoehoe lava flows. |- |2 |10,000–25,000 |alkali basalt with minor amounts of picritic basalt, hawaiite and ankaramite |5 |63 |northeastern and southwestern flanks |Lava spatter, cinders, extensively weathered aa and pahoehoe lava flows and palagonite tuff. Spatter and cinders contain abundant xenoliths of mafic and ultramafic plutonic rocks. |- |1 |more than 100,000 |trachyte |less than 1 |3 |northeastern flank |Trachyte cone of Pu u Wa awa a (current prominence approximately 430 metres). Block and aa trachyte lava flow of Pu u Anahulu and trachyte pyroclastic deposits. 5.5 km³ in volume, the largest-volume single eruption on Hawai i (Big island). K-Ar age is 106,000 ± 6,000 years before present. |}

1800–1801 eruption

Hualālai last erupted in 1800–1801. This eruption produced very fluid alkalic basalt lava flows that entered the ocean off the western tip of Hawai i island. Although five vents were active at the time, only two produced flows that eventually reached the ocean. The total output volume of the flow is estimated at over . One volcanic vent, situated high on the slope, produced a large a'a flow, dubbed the Kaʻūpūlehu flow, that reached the ocean as two distinct lobes. This 1801 flow, known as the Hu ehu e flow, formed Keahole Point where Kona International Airport is now located, north of Kailua-Kona. The eruption at Hualālai was concurrent with an eruption at the nearby Mauna Loa. It is theorized that, in the near past, Hualālai has had synchronous eruptions with both Mauna Loa and Kilauea.

Future monitoring

Although Hualālai last erupted almost 200 years ago, it will almost certainly erupt again in the near future, as a 200–300 year estimated pause in activity is coming to an end. The flanks of the volcano do not pose a lower threat to the population than the area near the rift zones because the distance is short and the slopes are steep; lava poses as much of a threat as it does near its source. The Kaloko-Honokōhau National Historic Park lies on the shore west of Hualālai, over the site of an ancient Hawaiian settlement. Although it is called kekaha ʻaʻole wai (lands without water), the rugged volcanic terrain attracted much sea life, making it an appealing place to settle. There are two main attractions within the park: the Kaloko fishpond, an area of loko kuapa (rockwall fishponds) constructed of interlocking rocks across a natural embayment on the coast, and Honokōhau, a former extensive settlement on the south side of the park.

ī]], court attendant of Kamehameha II.

Today, the coast west of Hualālai is a popular location for vacation resorts, since the rain shadow of the mountain causes many sunny days. The first, Kona Village resort, was built in 1961. Since then the Four Seasons Resort and the Kūki o golf course and vacation home complex have also been built on the 1800 flow. The Hawaii Belt Road traverses the western slopes with an upper route called the Mamalahoa Highway and lower route named for Queen Ka ahumanu.

Much of the Kona coffee crop grows on Hualālai's western slope near the town of Holualoa. The family of early coffee merchant Henry Nicholas Greenwell owned a large ranch on the western side of the volcano. The road from Kailua-Kona up the slopes of Hualālai is named for Frank "Palani" Greenwell. Hawaii Route 200 known as the Saddle Road, crosses the plateau north of Hualālai, where the Pohakuloa Training Area provides a remote training ground for the United States Army and United States Marine Corps.

Recreational significance

Hualālai's many interesting features, most especially its volcanic cones, make it a popular destination for hikers. Although it is relatively easy to climb, much of the land at and around the summit of the volcano is owned by Kamehameha Schools, which routinely denies access to hikers attempting to climb it. As most, if not all, routes up to Hualālai pass through the estate, hiking on Hualālai is more or less illegal. However, the laws are not stringently enforced, and many hikers slip through anyway.

One of the most popular mountaineering features is Luamakami and its sister Puhia Pele, two pit craters on Hualālai that are the deepest on the island. Puhia Pele, also known as "Pele's Pit", has been explored to a depth of , and Luamakami is known to be even deeper. The walls are scalable with the proper technical equipment. The summit gets more rain than the coast

The Honuaula forest reserve on the southwestern flank of the volcano at , preserves an extensive koa (Acadia koa) forest stand, with smaller Naio (Myoporum sandwicense) and Māmane (Sophora chrysophylla) trees and an undergrowth of Ākala (Rubus hawaiensis) and various ferns. The reserve measures and protects an ecosystem that has since been largely deforested in the surrounding area.

The Wai Aha spring reserve on the lower slopes of the mountain is somewhat swampy and is home to the flowering evergreen ōhiʻa (Metrosideros polymorpha), the woody climber Ie ie, and a dense undergrowth of Ama u (Sadleria cyatheoides).

References

of Hualālai volcano]]

External links

USGS page about Hualalai

Aerial photos of Hualalai

Category:Active volcanoes Category:Hotspot volcanoes Category:Mountains of Hawaii Category:Shield volcanoes Category:VEI-2 volcanoes Category:Volcanoes of the Island of Hawaii Category:Pleistocene volcanoes