Boiling Pots:
The Wailuku River is the second-longest river in Hawaii, flowing along the path where lava from Mauna Loa and Mauna Kea come together. Over time the river eroded a gorge between the two lava flows, which were also filled twice by younger lava flows from Mauna Loa. About one mile above Rainbow Falls, the Wailuku River drops over Pe’epe’e Falls into a series of flowing cascades called the Boiling Pots, whose waters tumble, roll, and bubble, making it appear like it’s boiling from underground lava tubes. The vertical columns that surround the Boiling Pots were formed as the lava cooled slowly in the river bed. The activity of the Big Island Boiling Pots are completely dependent upon the rains and the water flow. During light and heavy rains, the water will become turbulent and appear to bubble and boil near the depressions. In light rains or calm weather, you will mostly just see a succession of cascading pools along the river.
What are some types of lava?
ʻAʻā is one of four basic types of flow lava. ʻAʻā is basaltic lava characterized by a rough or rubbly surface composed of broken lava blocks called clinkers. The Hawaiian word was introduced as a technical term in geology by Clarence Dutton. The loose, broken, and sharp, spiny surface of an ʻaʻā flow makes hiking difficult and slow. The clinkery surface actually covers a massive dense core, which is the most active part of the flow. As pasty lava in the core travels downslope, the clinkers are carried along at the surface. At the leading edge of an ʻaʻā flow, however, these cooled fragments tumble down the steep front and are buried by the advancing flow. This produces a layer of lava fragments both at the bottom and top of an ʻaʻā flow. ʻAʻā is usually of higher viscosity than pāhoehoe. Pāhoehoe can turn into ʻaʻā if it becomes turbulent from meeting impediments or steep slopes. The name ʻaʻā originates from Hawaiian meaning “stony, rough lava.”
Pāhoehoe is basaltic lava that has a smooth, billowy, undulating, or ropy surface. These surface features are due to the movement of very fluid lava under a congealing surface crust. The Hawaiian word was introduced as a technical term in geology by Clarence Dutton. A pāhoehoe flow typically advances as a series of small lobes and toes that continually break out from a cooled crust. It also forms lava tubes where the minimal heat loss maintains low viscosity. The surface texture of pāhoehoe flows varies widely, displaying all kinds of bizarre shapes often referred to as lava sculpture. With increasing distance from the source, pāhoehoe flows may change into ʻaʻā flows in response to heat loss and consequent increase in viscosity.
Blocky lava is cool, stiff lava that does not travel far from the erupting vent. Blocky lava usually oozes from a volcano and forms jumbled heaps of sharp-edged chunks. They behave in a similar manner to ʻaʻā flows but their more viscous nature causes the surface to be covered in smooth-sided angular fragments (blocks) of solidified lava instead of clinkers. Like in ʻaʻā flows, the molten interior of the flow, which is kept insulated by the solidified blocky surface, overrides the rubble that falls off the flow front. They also move much more slowly downhill and are thicker in depth than ʻaʻā flows.
Pillow lava is the lava structure typically formed when lava emerges from an underwater volcanic vent or subglacial volcano or a lava flow enters the ocean, a lake, or another body of water. However, pillow lava can also form when lava is erupted beneath thick glacial ice. The viscous lava gains a solid crust on contact with the water, and this crust cracks and oozes additional large blobs or "pillows" as more lava emerges from the advancing flow. Since water covers the majority of Earth's surface and most volcanoes are situated near or under bodies of water, pillow lava is very common.
Logging Requirements:
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Use the information sign “Why is it Called Boiling Pots” at the GZ to complete this sentence: Boiling Pots refers to a series of pot-shaped holes eroded into the _____ ___ lava flow that filled the Wailuku River channel more than ______ years ago.
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What type of lava do you observe at this location, ʻaʻā, pāhoehoe, blocky lava, or pillow lava? Are there multiple types of lava at the GZ? If so, where are they located in the gorge?
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Was it a calm day, light rain, or heavy rain during your visit to Boiling Pots? How did this affect the landscape?
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Sources:
http://www.hilldale.k12.ok.us/vimages/shared/vnews/stories/5081b48c40831/ES_Section%209.1%20(Volcanic%20Eruptions%20pg.250-255).pdf
https://www.alltrails.com/trail/hawaii/hawaii/boiling-pots?u=i
https://inspiredimperfection.com/adventures/peepee-falls-and-the-wailuku-river-boiling-pots/
https://en.wikipedia.org/wiki/Lava#%CA%BBA%CA%BB%C4%81
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