# Wilkes Expedition Revisits Kīlauea

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The U.S. Exploring Expedition returned to Kīlauea last week, in the form of a riveting "After Dark in the Park" program delivered by Herman Viola of the Smithsonian Institution.

View of crater, Kīlauea by Artist: J. Drayton / Engraver: Jordan and Halpin.

(Public domain.)

In 1985, Viola led a team of scholars who spent four years assembling a Smithsonian exhibit and book about the expedition, both titled Magnificent Voyagers. The expedition explored much of the Pacific basin, including Hawai‘i, from 1838-42. The "Ex. Ex.," as it was known when the voyage set sail, is now more commonly referred to as the Wilkes Expedition after its leader, Lieutenant Charles Wilkes.

The expedition was motivated by a combination of commercial, diplomatic, and scientific concerns. One of its main objectives was to survey and make accurate charts of numerous Pacific island chains, the coastline of the Pacific Northwest, and the Antarctic region, where the existence of land at the South Pole was still a matter of dispute.

Nine civilian "Scientifics," including two artists, accompanied the expedition. Of this group, the scientist who would go on to make the biggest mark in his field was the geologist James Dwight Dana. Only 25 years old when he joined the expedition, Dana had already published his "System of Mineralogy," which he continued to revise throughout his lifetime, establishing the system of mineral classification that is still in use today.

Dana was responsible for the most significant scientific contributions produced by the expedition. Like his contemporary Darwin, he possessed a striking ability to synthesize many disparate observations into a single theory that brought the big picture into focus.

Independent of Darwin, he realized that coral atolls evolved from volcanic islands with fringing reefs. Moreover, during the many months that the expedition spent charting islands throughout the south Pacific, Dana came to recognize the significance of linear island chains and deduced the age progression within each chain.

With the advent of plate-tectonic theory more than a century in the future, however, Dana's explanation of the age progression of Hawaiian Islands fell short. Observing the progressive erosion of the islands as he sailed up the chain to the northwest, Dana erroneously concluded that all the volcanoes had formed simultaneously, then had become extinct starting from the northwest end of the chain.

Dana's contributions to the scientific success of the expedition transcended his own specialty. In the decade following the expedition, he wrote not only the report on geology, but also the volumes on coral and crustaceans. His experience in the Pacific led to a life-long interest in volcanology, culminating in an influential book on the subject written in his 70s.

The Wilkes Expedition is probably better known among scientists on the Big Island than by our counterparts anywhere else in the country. The expedition split up when it reached Hawai‘i and visited the Big Island in two parties. Dana's group spent only five days on the island, traveling overland from Kealakekua to Hilo, via the summit caldera of Kīlauea, which was then in constant eruption. In spite of the brevity of his visit, Dana gained key insights into the nature of Hawaiian volcanism.

We know what Kīlauea's caldera looked like at that time, thanks to Dana's shipmate, Titian Peale, an expedition naturalist and artist. Peale is a familiar name in Hawai‘i, because his many sketches and paintings of Kīlauea's summit have been widely reproduced in histories of the island.

Wilkes' ship, meanwhile, anchored in Hilo Bay for three months. With the help of the missionary Dr. Gerrit Judd, Wilkes assembled a large group of Hawaiian porters to ferry his cumbersome instruments and supplies to the summit of Mauna Loa, where the party camped for three weeks in mid-winter. In spite of horrific storms, Wilkes persevered, completing geophysical and meteorological measurements and producing the first map of Mokuaweoweo, Mauna Loa's summit caldera. The rock walls that the Wilkes party erected around their camp are still visible on the east rim of the caldera.

Two members of the expedition climbed Mauna Kea, and several others traveled the length of Kīlauea's east rift zone. The latter produced a map of the recent lava flow of 1840, which had traversed lower Puna and entered the ocean, forming the Nanawale Sand Hills. Their map remained the most accurate one of a Kīlauea eruption for almost a century.

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### Volcano Activity Update

This past week, activity levels at the summit of Kīlauea Volcano have remained at background levels. The summit caldera has been expanding, indicating inflation, since the beginning of 2007. The number of earthquakes located in the summit area is at low levels (usually fewer than 10 per day are large enough to locate).

Eruptive activity at Puu Oo continues. On clear nights, glow is visible from several vents within the crater. Lava is fed through the PKK lava tube from its source on the southwest flank of Puu Oo to the ocean. About 1 km south of Puu Oo, the Campout flow branches off from the PKK tube. The PKK tube feeds a long-lived ocean entry at East Laeapuki, while the Campout tube is the source for ocean entries East Kailiili and Kamokuna. All three ocean entries are located inside Hawaii Volcanoes National Park.

As of March 9, the East Kailiili entry was dead and East Laeapuki much diminished. Kamokuna is now the dominant entry. In the last week, intermittent breakouts from the Campout and PKK tubes have been seen on the slope of Pulama pali and on the coastal plain. A breakout from the Campout tube below the pali continues to host minor surface flows inland from the sea cliff at East Laeapuki and on the bench below.

Access to the sea cliff near the ocean entries is closed, due to significant hazards. The surrounding area, however, is open. If you visit the eruption site, check with the rangers for current updates, and remember to carry lots of water when venturing out onto the flow field.

One earthquake beneath Hawai‘i Island was reported felt within the past week. A magnitude-2.2 earthquake occurred at 11:01 a.m. H.s.t on Friday, March 9, and was located 9 km (6 miles) west of Waikoloa Village at a depth of 34 km (21 miles). It is the most recent of nearly 500 aftershocks from the October 15, magnitude-6.7 earthquake.

Mauna Loa is not erupting. During the past week, earthquake activity was at low levels beneath the volcano's summit (three earthquakes were located). Extension of distances between locations spanning the summit, indicating inflation, continues at slow rates.