Mauna Loa and Mauna Kea
Photo taken by Tim Lincoln
The Geology Department at Albion College organized a regional field trip to Hawaii from March 5th to March 14th 2003. Three professors, Thom Wilch, Tim Lincoln and Beth Lincoln, and eleven students went. The purpose of this regional study was to visit and see the landforms we had been learning about first hand. This web site is one of five made by the students on the trip. Each website touches on a different area we visited. Our website is focused on the two volcanoes on Hawaii called Mauna Kea and Mauna Loa.
The Mauna Loa volcano comprises more of the Hawaiian Big Island than any of the other 4 Hawaiian volcanoes, and is located primarily on the southern half of the island. Its long underwater flanks descend to the sea floor an additional 5 km, and the sea floor is depressed by Mauna Loa’s great mass another 8 km. This makes the volcano’s summit about 17 km (56,000 ft) above its base, making Mauna Loa the largest volcano in the world. In turn, the name Mauna Loa means “Long Mountain”. It reaches an altitude of 13,680 ft. Since 1843, this shield volcano has erupted 33 times, with the most recent of these eruptions occurring in 1984. It’s first eruption above sea level most likely occurred about 400,000 years ago. The volcano currently appears to be inflating, and could erupt at any moment. The oldest dated rocks on the volcano are between the ages of 100,000 and 200,000 years old. (http://hvo.wr.usgs.gov/maunaloa/)
Forming of the Black Sand Beach
The black sand beaches are made of a rock called basalt. The lava flows into the water and solidifies. Then the waves crash into the shore and the pahoehoe and aa flows start to erode. The rocks erode into coarse sand grains. Black sand beaches are short lived because of the new lava that flows over the beach and erodes into newer younger grains.
Photo by Beth Lincoln
Photo by Thom Wilch
Forming of Olivine Beaches
On Mauna Loa there was a prehistoric littoral cone called Pu’u o Mahana, which is the site of the Big Island’s green-sand beach. This littoral cone resulted from a special type of explosion, called a littoral explosion, which usually results when lava flows enter the ocean. Seawater comes into contact with the hot inner part of the lava flow and flashes into steam, triggering an explosive spray of fragments derived from both the solidified outer part of the lava flow as well as its still-molten core. The green beach gets its color from a green mineral called olivine. These olivine minerals are stuck in chunks of basalt. Sometimes these eruptions produce small deposits and since they take place on the seashore, most of these deposits are quickly eroded away by the waves. Larger deposits, like the one near the south tip of Hawaii, are harder to erode away.
Forming of the Boiling Pots
Boiling pots are steps of large, circular pools. Kind of like a series of potholes about 10 to 20 m in diameter. The first pool drops down into the second pool usually by a waterfall. All of the pools are in succession, flowing in route until they get to the ocean. These boiling pots that we saw were on the island of Hawaii right in Hilo off Pee Pee Falls Road. They are between the shields of Mauna Loa and Mauna Kea where there is a saddle called Humuula saddle, which forms a natural channel for rain runoff from the southern and southeastern flanks of Mauna Kea. Because of this runoff, a shallow gorge has been created along the edge of the Mauna Loa lava (which was later filled with a prehistoric flow). This last flow was eroded down by the Wailuku River, which formed the boiling pots.
When this prehistoric flow came in and filled in the stream channel, it made the stream rise to a level 6 to 10 meters below the channel top. The cooling of the flow made several distinct fracture zones. Since the cooling went from the bottom to the top, it formed long skinny columnar joints. Columnar joints form a hexagonal shape. These columnar joints were about 40 cm across and had a height of 10 to 12 meters. The other kind of fracture is one that I haven’t learned about in class yet.
Ryan, M.P., and Sammis, C.G., 1978, Cyclic fracture mechanisms in cooling basalt: Geological Society of America, v. 89, p.1295-1308.
Looking out at Mauna Kea
Photo by Jeremy Gouldey
The Hawaiian volcano of Mauna Kea is the highest volcano in the chain of islands. From sea level, it has a summit that reaches up to 13976 ft. Near the top, strong winds can be felt, which can rapidly change from 10 mph to 40 mph. The higher up you climb, the colder it gets, and the thinner the air becomes, conditions you usually don’t think about when you think of Hawaii. The climb to the top is a hard, slippery one, but the view is definitely worth it. It is best place on the island to get out the heat and see some real Hawaiian snow.
Mauna Kea has many significant geological features. Glacial moraines exist on the volcano, as the big island of Hawaii went through a stage of glacial activity. This is evidence of the existence of glaciers on the volcano at some point in time. In fact, 4 episodes of glaciation are recorded on the mountain. Upon reaching the summit, Mauna Kea’s true splendor is revealed. As you look around, you can see cinder cones all around. The crater rims around the summit are of different height, giving evidence that the cinder cones probably each formed within a matter of days. The summit itself appears to be partly comprised of reddish rocks, and upon closer inspection, contains pyroxene and possibly some olivine. The mountain is made up of basaltic rock, originating from basaltic lava flows which have occurred over time. Many well developed bombs can be found lying about, as well.
Jeremy and Sierra on Mauna Kea summit, with Mauna Loa and cinder cones in the background
Atop Mauna Kea, hanging loose, from left to right
Top: Prof. Wilch, John
Bottom: Steve, Karen, Jeremy
The Mauna Kea volcano has been used for a variety of purposes. It is one of the most important sites for the advancement of astronomy, and a prime location for studying the sky. The summit is spotted with several large observatories, many run by other countries besides the United States. It was long ago used as an adz quarry, as the Polynesian people mined the basalt to produce various tools and weapons. Early settlers also inhabited many of the caves on the mountain. The peak of the volcano was also a site of worship, as the early Polynesians climbed the peak to give gifts and sacrifices to the god Pele. Mauna Kea is an important site for geological and biological study as well. The most unusual feature on the mountain is a large lake that sits 13,000 ft above sea level. What’s peculiar about this lake it that within it, algae has survived and thrives. This is the highest altitude algae has been reported at, and until this discovery, this was thought impossible. (Mauna Kea Visitor Center)
Sierra looking up Mauna Kea summit, where rest of group struggles to make it back down.
Sierra posing at Polynesian worship spot, Steve and Karen gazing out towards Mauna Loa, and international observatories in the distance.
Photos taken by Jeremy Gouldey
On Mauna Kea, there are two major waterfalls, the Akaka Falls and the Kahuna Falls, each forming near each other. The two falls can be found by hiking through an area of beautiful vegetation. Akaka Falls has a height of 442 ft, while Kahuna Falls has a height of about 400 ft. The falls empty into the Wailuku River, which forms the boundary between Mauna Loa and Mauna Kea. The falls originated from dense aa lava flows, as opposed to pahoehoe flows, and the stream in which they empty into has revealed old lava flows on the bottom by cutting through layers of ash.
Sierra standing in front of beautiful Akaka Falls.
Jeremy and Sierra on the path that connects Akaka and Kahuna Falls.
Photos taken by Jeremy Gouldey