Volcano Watch — Youngest flows in Haleakalā Crater about 800-1,000 years old

The story is told of how Maui snared the sun, holding it hostage atop Haleakalā until he slowed its passage across the sky. One result of this slow burn is a barren, rocky landscape devoid of soil or vegetation. Geologically speaking, the devastation resulted as numerous cinder cones and fissures erupted lava that flowed across the crater floor. How young are these flows?

This past year, scientists from the U.S. Geological Survey's Hawaiian Volcano Observatory collected charcoal from beneath several of the lava flows. The charcoal was created when lava ignited and buried vegetation in its path. The resulting ages, determined by the carbon-14 method of isotopic dating, provide this answer: the crater's floor is mantled by flows chiefly younger than 4,070 years.

The 4,070-year age is from the lava erupted at Pu`u Maile, a cinder cone on the central crater floor east of Kapalaoa Cabin. Only about a dozen of the crater-mantling cones and flows are thought to be older, on the basis of their more highly vegetated surfaces compared to the Pu`u Maile lava. Some of the older features include Pu`u Mamane, Mauna Hina, Namana o ke Akua, and Honokahua. Finding charcoal beneath the older cones and flows is almost impossible because their margins have been buried by younger lava, thereby hiding the tell-tale charcoal beneath tons of rock.

The youngest age so far is about 870 years, from a fissure system that traverses the central crater floor and north crater wall near the peak known as Hanakauhi. This fissure is probably the youngest eruptive feature in the eastern part of the crater.

In contrast to the eastern crater, the youngest lava in the western crater remains undated. This lava issued from a vent on the north side of Ka Lu`u o ka `O`o, a prominent cinder cone accessible by a two-mile hike from the summit visitor center. The Ka Lu`u lava oozed downslope toward Holua Cabin, where it buried a slightly older lava emplaced about 970 years ago. Thus the Ka Lu`u lava is only known to be younger than about 970 years in age.

Could the Ka Lu`u flow be younger than the 870-year-old Hanakauhi fissure? The two flows are nowhere in contact with each other, so their ages relative to each other are unknown. The Ka Lu`u flow lies in a high, dry part of the crater, an area with little vegetation now and probably comparably sparse vegetation at the time the flow was active. It's unlikely that charcoal for dating will be found there, so additional techniques will be required to gain an answer.

The other ages obtained from the crater this past year are mostly in the range of 1,000-3,000 years. For example, a lava from Pu`u Nole poured eastward into Kaupo Gap about 1,160 years ago. It banks against the 4,070-year-old Pu`u Maile flow and, in turn, is overlain by the 870-year-old Hanakauhi lava.

Younger eruptions have occurred on East Maui, with the most recent about 200 years ago near La Perouse Bay. Several other flows higher on the southwest rift zone were active about 500 years ago, as were flows near Hana on the east side of the island. But in Haleakalā Crater, our best information so far indicates activity only as recently as 800-1,000 years ago.

Volcano Activity Update

Eruptive activity was visible within Pu`u `O`o during the past week with lava rising and falling in three separate vents on the crater floor. Through a network of tubes, the lava flows from the vents to the seacoast and enters the ocean at two locations-Waha`ula and Kamokuna. The public is reminded that these two ocean-entry areas are extremely dangerous, and the National Park Service has restricted access to them because of frequent explosions accompanying collapses of the growing lava delta. The highly-acidic steam plume is laced with glass particles.

An earthquake was felt by a resident of Keauhou, Kona at noon on Monday, May 11. The epicenter of the magnitude 4.0 earthquake was 49 km (29.4 mi) west of Keauhou at a depth of 38 km (22.8 mi).