Editing Mauna Loa (section)

===Wilkes expedition===
[[File:Wilkes campsite.jpg|thumb|upright=1.5|Sketch of Wilkes' campsite by ship's artist [[Alfred Thomas Agate]]]]

The [[United States Exploring Expedition]] led by Lieutenant [[Charles Wilkes]] was tasked with a vast survey of the Pacific Ocean starting in 1838.<ref>{{cite book| title=Narrative of the United States Exploring Expedition |author=Charles Wilkes |year=1849 |volume=IV |pages=111–162| url=https://books.google.com/books?id=lbMNAAAAQAAJ| publisher=G. P. Putnam}}</ref> In September 1840 they arrived in [[Honolulu]], where repairs to the ships took longer than expected. Wilkes decided to spend the winter in Hawaii and take the opportunity to explore its volcanoes while waiting for better weather to continue the expedition. King [[Kamehameha III]] assigned American medical missionary Dr. [[Gerrit P. Judd]] to the expedition as a translator.<ref name="measuring"/>

Wilkes sailed to [[Hilo]] on the [[Hawaii (island)|island of Hawaiʻi]] and decided to climb Mauna Loa first, since it looked easier than [[Mauna Kea]]. On December 14 he hired about 200 porters, but after he left he realized only about half the equipment had been taken, so he had to hire more Hawaiians at higher pay. When they reached Kīlauea after two days, their guide Puhano headed off to the established ʻAinapō Trail. Wilkes did not want to head back downhill so he blazed his own way through dense forest directed by a compass. The Hawaiians were offended by the waste of sacred trees which did not help morale. At about {{convert|6000|ft|m}} elevation they established a camp called "Sunday Station" at the edge of the forest.

Two guides joined them at Sunday Station: Keaweehu, "the bird-catcher" and another whose Hawaiian name is not recorded, called "ragsdale". Although Wilkes thought he was almost to the summit, the guides knew they were less than halfway up. Since there was no water at Sunday Station, porters had to be sent back ten miles (16&nbsp;km) to a [[lava tube]] on ʻAinapō Trail which had a known supply. After an entire day replenishing stocks, they continued up to a second camp they called "Recruiting Station" at about {{convert|9000|ft|m}} elevation. After another full day's hike they established "Flag Station" on December 22, and by this time were on the ʻAinapō Trail. Most of the porters were sent back down to get another load.

At the Flag Station Wilkes and his eight remaining men built a circular wall of lava rocks and covered the shelter with a canvas tent. A snowstorm was in progress and several suffered from [[altitude sickness]]. That night (December 23), the snow on the canvas roof caused it to collapse. At daylight some of the group went down the trail to retrieve firewood and the gear abandoned on the trail the day before. After another day's climb, nine men reached the rim of Mokuʻāweoweo. They could not find a way down its steep sides so chose a smooth place on the rim for the camp site, at coordinates {{coord|19|27|59|N|155|34|54|W| type:landmark_region:US-HI| display=inline}}. Their tent was pitched within {{convert|60|ft|m}} of the crater's edge, secured by lava blocks.<ref name="focus">{{cite web| author=Russell A. Apple
|url={{NRHP url|id=74000295}} | title=Wilkes Campsite Nomination form | work=National Register of Historic Places | publisher=National Park Service |year=1973}}</ref>

The next morning they were unable to start a fire using friction due to the thin air at that altitude, and sent for matches. By this time, the naval officers and Hawaiians could not agree on terms to continue hiring porters, so sailors and marines were ordered from the ships. Dr. Judd traveled between the summit and the Recruiting Station to tend the many who suffered from altitude sickness or had worn out their shoes on the rough rock. Christmas Day was spent building rock walls around the camp to give some protection from the high winds and blowing snow. It took another week to bring all the equipment to the summit, including a [[pendulum]] designed for measuring slight variations in gravity.<ref name="focus"/>
[[File:Moku-A-Weo-Weo.jpg|thumb|right|Sketch of Mokuʻāweoweo from Wilkes' journal]]

On December 31, 1840, the pre-fabricated pendulum house was assembled. Axes and chisels cut away the rock surface for the pendulum's base. It took another three days to adjust the clock to the point where the experiments could begin. However, the high winds made so much noise that the ticks could often not be heard, and varied the temperature to make measurements inaccurate. Grass had to be painstakingly brought from the lowest elevations for insulation to get accurate measurements.

On Monday, January 11, Wilkes hiked around the summit crater. Using an optical method, he estimated Mauna Kea was {{convert|193|ft|m}} higher, while modern measurements indicate a difference of about {{convert|125|ft|m}}.<ref name=maunakea/> On January 13, 1841, he had "Pendulum Peak, January 1841 U.S. Ex, Ex." cut into a rock at the site.
The tents were dismantled and Hawaiians carried the gear down over the next three days, while Wilkes enjoyed a [[lomilomi massage]]. He continued his measurements at lower elevations and left the island on March 5. For all the effort he did not obtain any significant results, attributing gravity discrepancies to "the tides".<ref name="measuring"/>

The Wilkes expedition's camp site's ruins are the only known physical evidence in the Pacific of the U.S. Exploring Expedition.<ref name="focus"/> The camp site was listed on the [[National Register of Historic Places]] on July 24, 1974, as site 74000295,<ref name="nris">{{NRISref|2009a}}</ref> and is state historic site 10-52-5507.<ref>[http://hawaii.gov/dlnr/hpd/register/reghaw.pdf Historic Places in Hawaii County] on official state web site</ref>