Page 91 - Volcano and Geothermal Tourism

68 The Americas

of world‑class astronomical observatories. The walls which insulate the core and create a conduit
exceptional air quality, lack of extraneous ambient for the lava to continue flowing through (Cas and
light sources, height and relatively easy access make Wright, 1987). The hardened lava tube exterior
Mauna Kea’s summit the premier location for insulates the still molten lava within its walls,
astronomical observation on Earth (University of enabling the lava to travel significantly farther than
Hawai‘i Institute for Astronomy, 2009). it would if exposed to cool air, broadening the
Mauna Loa, at 4170m, is the world’s largest flanks of the volcano. Thus, without lava tubes, the
active volcano (USGS, 2006). Mauna Loa has Big Island’s volcanoes would be much steeper and
erupted nearly 40 times since 1832 with its last would form much smaller islands (Hazlett and
eruption in 1984 (Hazlett and Hyndman, 1996). Hyndman, 1996). As an eruptive event wanes and
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Kllauea volcano has erupted regularly since the supply of lava stops, the molten lava drains
prehistoric times (USGS, 2009). Recognized as away, leaving an empty tube similar to a water
one of the most active volcanoes in the world hose when the water is turned off. The size of a
(USGS, 2009), geotourism to the Big Island lava tube is influenced by the slope on which it
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climbs dramatically whenever Kllauea’s eruption flows, the rate the flow cools and the thickness and
becomes more spectacular. Conversely, when viscosity of the flow (Bullard, 1977).
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Kllauea’s volcanic activity pauses for a short The second lava tube forming process involves
period, geotourism to the island declines markedly. the inflation of leading edges of sheet flows of
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Thus, the nature of Kllauea’s eruption is intimately pahoehoe lava. As the flow velocity decreases due
intertwined not only with visitor attendance to to outbreaks of lava moving rapidly away from the
Hawai‘i Volcanoes National Park, but with the source, a thin crust quickly forms over the slow
overall economic health of the Big Island. moving, cooling lava. After the crust reaches a
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Hualalai, at 2521m, is located on the western thickness of 2–5cm, it becomes rigid and is strong
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side of the island. Hualalai is considered to be a enough to retain incoming lava, thus increasing
possibly dangerous volcano potentially erupting the hydrostatic head at the front of the flow (Hon
again within the next 100 years and menacing et al, 1994). The ‘increased hydrostatic pressure is
nearby resorts and residential areas (USGS, 2001). distributed evenly through the liquid lava core of
An extinct volcano, Kohala at 1670m is the the flow, resulting in uniform uplift of the entire
oldest volcano on the Big Island, with a last sheet‑flow lobe… As the flow advances, preferred
eruption dated at about 120,000 years ago (USGS, pathways develop in the older portions of the
1998). Major lava tube caves can be found on all liquid‑cored flow’ (Hon et al, 1994, p351). These
of the island’s volcanoes except Kohala (Halliday, pathways can evolve into lava tube systems in only
2004). a few weeks. If the sheet flow stops advancing due
to a decrease in eruption activity at the source, the
Lava tube formation tube remains filled with lava that hardens and
There are basically two types of basaltic lavas: blocks the tube, rather than draining to form a lava
‘a‘a lava is rough, sharp and blocky and rarely tube (Hon et al, 1994).
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makes lava tubes while pahoehoe lava is smooth
and ropey and frequently makes lava tubes (Bullard, Big Island lava tube values
1977). The Big Island of Hawai‘i is the world’s most
The first lava tube formation process begins important location for lava tube cave research and
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when pahoehoe lava creates a lava channel which contains the world’s most scientifically valuable
crusts over from contact with the cooler lava tube systems (Halliday, 2004). The island also
surrounding air. The crust forms a roof beneath contains more lava tubes than any other Hawaiian
which molten lava continues to flow. Thermal and island (Stone and Howarth, 2005). The two
physical erosion deepens the channel. The lava longest lava tubes in the world, Kazumura, with a
within the channel core remains fluid and hot as length of at least 65.5km (Shick, 2008) and the
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the outer edges cool, thicken and solidify, forming K lpuka Kanohina lava tube system, with a length

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