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Volcanowatch

June 17, 2004

A weekly feature provided by scientists at the Hawaiian Volcano Observatory.


Kilauea Overlook: a different view

Many readers have visited the overlook in front of the Jaggar Museum, next door to HVO, and those of you who haven't should do so some time. A grand vista of Kilauea's caldera awaits you, and many other sightseers as well. The hustle-bustle is commonly a little distracting.

There's another viewpoint that is usually quiet, contemplative, and educational. It's also a good place for a picnic. The next time you are on the way to Jaggar from the park entrance, turn off Crater Rim Drive first to visit Kilauea Overlook atop Uwekahuna Bluff.

Walk from the parking lot to the overlook itself. From there, a grand vista of Kilauea's caldera lies before you. The caldera formed in about A.D. 1500, when the summit of the volcano collapsed. The summit was probably a few tens of meters (a couple of hundred feet) higher that you are now. Before A.D. 1500, you would have had to look up to the top of the volcano from here.

The steep cliffs are faults that dropped the top of the volcano down to create the caldera. Today it is about 120 m (400 feet) to the floor of the caldera below the overlook, but it was probably several times that deep just after the caldera formed. Eruptions since then have filled in the caldera to its present depth. The darkest lava flows, on the far side of the caldera, were erupted in 1971 and 1974. The flows directly beneath the overlook, and covering most of the northern part of the caldera, date from 1919 and record the largest spill from Halemaumau in the 20th century.

The caldera is about 3 km (2 miles) across. You can see Kilauea Iki and Keanakako`i Craters on the other side of the caldera. But, if you turn around, you'll see a low cliff that the road descends into the parking lot; the picnic shelter is built against it. That cliff is one of the many faults that moved to drop down the caldera.

Really, then, the overlook, as well as Jaggar, HVO, and all the buildings along Crater Rim Drive, are inside the actual caldera. Several of the outermost faults of the caldera can be seen at Namakani Paio Campground, in the cliff across Highway 11 from the entrance station, and in the little rise in the Chain of Craters Road just before Puhimau Crater.

From Kilauea Overlook, the recently formed cones at Kilauea Iki (Pu`u Pua`i, 1959) and Mauna Ulu (1969-1974) are visible in the distance. Pu`u Pua`i is red-orange in color and directly across the caldera; Mauna Ulu is the bare shield well down the east rift zone.

Looking clockwise, Halemaumau is nicely visible from the overlook, as is the upper southwest rift zone from Cone Peak to Pu`u Koa`e. Note also the tilted fault blocks below Jaggar, shown as the sloping surfaces bounded by cliffs facing the caldera.

You may have noticed a large rock along the overlook path near the crossing of Crater Rim Trail. This rock is nearly 2 m (6 feet) across and was not brought here by park rangers to confuse us. The rock was instead thrown out by explosions during a tumultuous time in the late 18th century, possibly in 1790. Look around, and you'll see many more rocks in the area, too, though most are smaller than the giant. All of the sand was also exploded from the volcano.

Some of these rocks were of a quality useful to people for making sharp-edged instruments, such as adzes and scraping tools. Archaeologists have found many sites between here and Bird Park where people manufactured implements from the rocks thrown out to them by explosions.

If you want to reach the top, walk south on the paved Crater Rim Trail to Uwekahuna triangulation station, the highest point on Kilauea, constructed by the Hawaiian Territorial Survey during the early days of map-making in the islands. Along the way, you'll see a large, fern-filled crack related to the formation of the caldera--but watch your step, the explosion deposits along the crack are slippery.

A final tip: the restroom at the parking lot is usually less crowded than the one at Jaggar Museum.

Activity update

Eruptive activity at Pu`u `O`o continues. The Banana flow, which breaks out of the Mother's Day lava tube a short distance above Pulama pali, is entering the ocean in two areas off the 2002 Wilipe`a lava delta. In addition, lava has been visible between Pulama pali and Paliuli for the past week. The national park has marked a trail to within a short distance of the end of the flow, and thousands have been enjoying the show. Monday night a lava flow started down Pulama pali, and by Thursday was within 1 km (0.6 miles) of Paliuli. Eruptive activity in Pu`u `O`o's crater is weak, with sporadic minor spattering and small flows.

Only one earthquake was reported felt on the island during the week ending June 16. That was a small, magnitude-2.1 shake that took place at 6:12 a.m. June 15 and was felt at Leilani Estates. The earthquake was located 5 km (3 miles) west of `Opihikao at a depth of 4 km (2 miles).

Mauna Loa is not erupting. The summit region continues to inflate slowly. Seismic activity remains low, with only 1 earthquake located in the summit area during the past week.

Visit our website (hvo.wr.usgs.gov) for daily volcano updates and nearly real-time earthquake information. skip past bottom navigational bar


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Updated: July 15, 2004 (pnf)