Pu‘ukoholā Heiau National Historic Site EarthCache

FREE ADMISSION!! Pu'ukohola Heiau National Historic Site is open daily year-round 7:45am-4:45pm (including all Federal Holidays). The Park entrance gate closes by 4:00pm daily and all vehicles need to be out of the parking lot by 5:00pm. Ranger directed Educational Programs (elementary-college) must be scheduled in advance.

While this site is considered one of the most important heritage and cultural sites of Hawai‘i, the geological lessons we can learn here are numerous! As I was reading over the geological information provided by the National Park Service, I had a hard time choosing which one I wanted to highlight. My choices were fairly widespread:

Hawai‘i is the only location in the United States that contains anchialine pool habitat. Of the approximately 700 known Hawai‘ian anchialine pools, most are on the Island of Hawai‘i.

The availability of important, fresh groundwater resources on the Island of Hawai‘i depends on the age and geologic structure of a given area.

Many natural phenomena pose threats to coastal and near-coastal areas of the Hawai‘ian Islands. Among these hazards are volcanism, mass wasting, coastal erosion, tsunami inundation, sea-level rise, and seismic activity (Richmond et al. 2008).

Pu‘ukohola Heiau National Historic Site is underlain by lava flows from Kohola and Mauna Kea volcanoes, both of which are considered dormant.

Hawai‘i is the most seismically active place in the United States, with thousands of detectable tremors beneath the Island of Hawai‘i each year.

I asked Greg (the park ranger I've been talking with) what the most important geological aspect of the park was to him. He replied, "For me, the most important geologic aspect of the park is that the park sits on the dividing line between Mauna Kea and Kohala volcanoes (Most of the park is on Mauna Kea, but the John Young Homestead area is on Kohala)."

After reading through the geological information from the NPS and talking with Greg, I decided to highlight the Geological History of this historic site.

In geologic terms, the rock units in Pu‘ukohola Heiau National Historic Site are young—dating back as many as 700,000 years. Volcanism created the oldest of the rocks on the Island of Hawai‘i less than 1 million years ago, compared to more than 4 billion years of Earth’s history.

Although some of the Hawai‘ian Islands were built by a single volcano, others are a composite of several. Today, the Island of Hawai‘i is comprised of five volcanoes above sea level; a sixth, extinct volcano lies submerged north of Kailua. To the south of the island the active Lo‘ihi volcano has grown to within 1 km (0.6 mi) of the ocean surface. Active volcanoes remain active over a long period of time (hundreds of thousands of years).

The Pacific plate now covers about 20% of the Earth's crust, and is the largest tectonic plate on the planet. There are linear chains of volcanic islands and seamounts (submerged volcanoes) throughout the Pacific basin. Many of these chains change in age from one end to the other, due to their formation on plates moving over hotspots.

Hotspots form in response to plumes of material rising at very high temperature from the lower mantle, just above the core-mantle interface. These plumes are thought to form as a result of localized thermal disturbances in the molten core of the Earth. A part of the core transfers heat to the overlying mantle, which then rises, owing to its decreased density. Once a plume reaches the shallow depths in the mantle .200 km (125 mi), the drop in pressure causes the material to melt. If this molten 22 NPS Geologic Resources Division material (magma) finds a way to the outer crust it may erupt and produce a chain of volcanoes where the tectonic plate moved over the hotspot. The linear trend of the Hawai‘ian-Emperor islands and seamounts records the movement of the Pacific plate over such a stationary hotspot.

Each volcanic island in the Hawai‘ian chain evolved through four idealized eruptive stages: the preshield, shield, postshield, and rejuvenated stages.

Volcanic activity is still a remote possibility at Pu‘ukohola Heiau National Historic Site. The youngest flows from the nearby Hualalai Volcano reached the coast south of the park boundary, near Keahole Point, in 1801. Mauna Kea is considered dormant, not extinct. Recent flows from vents along the flanks of Mauna Loa are notoriously long, stretching from as far southeast as Hilo (1880-1881), to as far northwest as the west coast north of Hualalai (1859). The rocks exposed within Pu‘ukohola Heiau National Historic Site demonstrate the overlapping nature of volcanic growth within the Hawai‘ian Islands. The park straddles the stratigraphic boundary between Pleistocene volcanic lava flows from Kohala and Mauna Kea volcanoes.

In order to log this cache, you need to answer questions 1, 2, and 3 as well as ONE from 4, 5 or 6. Please do not answer in your log notes, but through a message to me through my profile (email must arrive within 24 hours of your log posting or your log will be deleted):

1. What natural phenomenon caused the volcanic debris used in the construction of Pu`ukohola Heiau to become rounded?

2. What type of rock is primarily used for creating Pu‘ukohola Heiau?

3. Please observe the rock from the 2 different volcanic fields (Kohala - John Young Homestead area, and Mauna Kea - Pu‘ukohola Heiau area) composing this historical site. What is the main difference between the rocks?

4. Approximately how many miles away was the source of stones for the building of Pu`ukohola Heiau?

5. The walls of Pu`ukohola Heiau & Mailekini Heiau are slanted inward because the Hawaiians lacked what important building substance?

6. Which important stone in the park was accidentally broken in 1937?

7. OPTIONAL: Submit a picture of Pu‘ukohola Heiau - bonus points if your photo contains members of your party. Photo should be submitted with your cache log!

Mahalo!!
Kateriana

Official Website: Pu‘ukohola Heiau National Historic Site

A HUGE Mahalo to Greg Cunningham, Park Ranger, for all the help!

Most Used Resource: Thornberry-Ehrlich, T. 2011. Pu‘ukohola Heiau National Historic Site: geologic resources inventory report. Natural Resource Report NPS/NRPC/GRD/NRR— 2011/386. National Park Service, Ft. Collins, Colorado.

 

Gratz to wholagal for FTF!!

Counter Added 6/19/2012

 

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