Hualālai

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Hualālai
North face of Hualālai as seen from Waimea
Elevation	8,271 ft (2,521 metres)
Location	Hawaiʻi, USA
Range	Hawaiian Islands
Prominence	2,473 m
Coordinates	19°41′32″N, 155°52′02″W
Topo map	USGS Hualālai
Type	Shield volcano
Age of rock	<100,000 years
Last eruption	1801

Hualālai is the third-most historically active shield volcano on the Island of Hawaiʻi in the Hawaiian Islands. Its peak is at 8,271 ft (2,521 m) above sea level. Hualālai lies more or less due west of the saddle between the much taller Mauna Kea and Mauna Loa mountains, and forms the backdrop to the town of Kailua-Kona. In fact, the town is built on the southwestern slope of this mountain, where most of the world famous Kona coffee is grown.

1 Structure
2 Recent eruptions
3 References
4 External link

[edit] Structure

Hualālai is built from a well-defined rift zone that trends approximately N50°W across its summit and a less well-defined rift zone that trends northward from a point 3 mi east of the summit (Macdonald and Abbott, 1970). The oldest dated rocks on the mountain surface are about 128,000 years before present (0.1 MYA). It is estmated that the volcano appeared above sea level some 300,000 years ago (0.3 MYA; USGS).

Over 100 cinder and spatter cones are arranged along the rift zones. There is no summit caldera, just a collapse crater (~ 0.3 mile across) at the top of a small lava shield. Much of the southern slope (above the town of Kailua-Kona) consists of lava flows covered by a layer of volcanic ash from 10 cm (a few inches) to a meter (3 ft) thick. Hualālai appears to have entered the late stage of the eruptive cycle of Hawaiian volcanoes (Macdonald and Abbott, 1970)—the post-shield stage (USGS).

[edit] Recent eruptions

Six different vents erupted lava between the late 1700s and 1801, two of which generated lava flows that poured into the sea along the west coast of the island. The Keahole Airport, located only 11 km (7 mi) north of Kailua-Kona, is built atop the smaller Huehue flow (1801) just north of Keahole Point (USGS, 1997).

Although Hualālai is not nearly as active as nearby Mauna Loa or Kīlauea, recent geologic mapping of the volcano shows that 80 percent of the mountain surface is covered by lava flows no older than about 5,000 years. In the past few decades, when most of the resorts, homes, and commercial buildings were built on the flanks of Hualālai, earthquake activity beneath the volcano has been low. In 1929, however, an intense swarm of earthquakes lasting more than a month was most likely caused by magma rising to near the surface. For these reasons, Hualālai is considered a potentially dangerous volcano that is likely to erupt again sometime in the next 100 years (USGS).

[edit] References

Macdonald, G. A. and A. T. Abbott. 1970. Volcanoes in the Sea. Univ. of Hawaiʻi Press. 441 pp.
USGS website: Hualālai, Hawaiʻi's Third Active Volcano