Diamond Head Crater EarthCache
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Diamond Head is the name of a volcanic tuff cone on the Hawaiian island of O'ahu and known to Hawaiians as Le'ahi, most likely from lae “browridge, promontory” plus 'ahi “tuna” because the shape of the ridgeline of the crater as seen from Waikiki resembles the shape of a tuna's dorsal fin.
Le'ahi can also mean "wreath of fire" and refer to the navigational fires lit on the summit to assist canoes travelling offshore.
Its English name was given by British sailors in the 19th century, who mistook calcite crystals embedded in the rock of the craters for diamonds. Thus, the name Diamond Head was born.
Hours: Daily 6:00 a.m. to 6:00 p.m., Every day of the year including holidays. Last entrance to hike the trail is at 4:30 p.m. The gates are locked at 6:00 p.m. daily and all visitors must be out of the park by this time.
NOTE: State Parks is planning to start a second phase of improvements to the historic summit trail at Diamond Head State Monument, beginning November 8, 2010. The project is expected to take approximately 60 days, during which time the trail will remain open weekday mornings and on weekends.
Entrance Fee: $10.00 per car or $5 per person for pedestrians.
Congratulations to 55CONNIE and peakbagginggeo for being the first to visit the site of this EarthCache listing after it was published and completed the logging requirements!!
GEOLOGICAL FACTS:
The creation of O'ahu began around 3 million years ago when 2 shelf volcanoes erupted. The Wai'anae and Ko'olau Mountain Ranges are the very eroded remnants of these volcanoes.
About 500,000 years ago, eruptions began along the Ko'olau rift zone. It was during one of these eruptions that the tuff cones of O'ahu started to form.
There was an explosive volcanic eruption on the flanks of the Ko'olau Mountains about 300,000 years ago. During this eruption, large amounts of ash and fine particles were sent into the air. As these particles settled around the center of the eruption, an ash cone crater was created. When the ash and fine particles settled, they were cemented into rock called "tuff." Thus, Diamond Head is an example of a tuff cone.
An ash cone is composed of particles of silt to sand size. Explosive eruptions from a vent where the magma is interacting with groundwater or the sea (as in an eruption off the coast) produce steam and are called phreatic. The interaction between the magma, expanding steam, and volcanic gases results in the ejection of mostly small particles of ash. The fallen ash has the consistency of flour. The unconsolidated ash forms an ash cone which becomes a tuff cone or tuff ring once the ash consolidates. Flat-floored craters that scientists interpret have formed above diatremes as a result of a violent expansion of magmatic gas or steam; deep erosion of a maar presumably would expose a diatreme.
Diamond Head is part of the complex of cones, vents, and their associated eruption flows that are collectively known to geologists as the Honolulu Volcanic Series, eruptions from the Ko'olau Volcano that took place long after the volcano formed and had gone dormant. The Honolulu Volcanic Series is a series of volcanic eruption events that created many of O'ahu's well-known landmarks, including Punchbowl Crater, Hanauma Bay, Koko Head, and Manana Island in addition to Diamond Head.
Diamond Head, like the rest of the Honolulu Volcanics, is much younger than the main mass of the Ko'olau Mountain Range. While the Ko'olau Range is about 2.6 million years old, Diamond Head is estimated to be about 150,000 years old and extinct for 150,000 years.
The eruption that built up Diamond Head was probably very brief, lasting no more than a few days. It was probably explosive, since when the cinder cone was originally formed, the sea level is thought to have been higher and the vent burst erupted over a coral reef. Another factor probably contributing to the eruption's explosive nature was that rising magma would have come into contact with the water table. The eruption's relatively brief length is thought to explain why the cone today is so symmetrical.
A nearby eruption that took place at about the same time as the Diamond Head eruption was the eruption that built the Black Point lava shield. Since the type of eruptions that built Diamond Head tend to be monogenetic, geologists don't believe Diamond Head will erupt again.
The broad crater covers 350 acres with its width being greater than its height. The southwestern rim is highest because winds were blowing the ash in this direction during the eruption. Since the eruption, the slopes of the crater have been eroded and weathered by rain, wind and the pounding sea.
A coral reef now helps protect the seaward slopes of the crater. But intense storms, with heavy rains and runoff, continue to deepen the gullies on the slopes of the crater. An estimated 100 feet have been eroded from the summit. The erosion of Diamond Head is hastened by the millions of feet that walk through the crater every year. Please help slow the erosion by staying on the marked trail.
BONUS MILITARY HISTORY:
Hawai'i has been an important site for coastal defense in the Pacific since the late 1800s. The Army Corps of Engineers began the construction of 4 forts between Honolulu and Pearl Harbor in 1908. The batteries at these forts housed large caliber artillery to defend O'ahu from an ocean attack.
Diamond Head was selected as a fortification because it's crater walls are a natural defense and from it's summit, ships could be seen from Koko Head to Pearl Harbor. Fort Ruger began in 1908 with the construction of Battery Harlow on the outer slopes of the crater and Fire Control Station Diamond Head at the summit.
The motars at Battery Harlow were aimed to fire over the crater and far out into the channel south of O'ahu. With a range of 8 miles, the mortars could reach both Honolulu and Pearl Harbor. The target locations were plotted and transmitted from the Fire Control Station at the summit.
Three more batteries were built during World War I and one more during World War II. All the artillery was dismantled in 1950. The crater was a restricted military reservation from 1906 to 1976. After which a portion of the crater was opened for recreation use in 1976. Other areas are still used by Civil Defense, the FAA and the Hawai'i National Guard, and are still restricted.
To claim this earthcache you need to go to the locations listed and answer the following question. Email your answers to Martin 5. You are also asked to please post a picture of yourself at the summit.
OPTIONAL (EXTRA CREDIT) THINGS YOU CAN DO TOO:
BONUS QUESTIONS 1 - 2 CAN BE ANSWERED FROM THE AREA OF #1.
1) In what year was Diamond Head declared a National Natural Landmark?
2) How many times were the artillery guns fired during World War II?
BONUS QUESTION 3 CAN BE ANSWERED FROM THE AREA OF #5.
3) How many stairs are there at #5?
- There is a virtual cache you can log at #1. (Diamond Quest - GCA4D4)
- There is a geo-cache at #11 you can find. (Leahi Peak (Diamond Head) - GCG3EE)
- There is a benchmark at #12 you can log on geocaching.com.
Have fun!!
PLEASE NOTE: IF YOU VISITED DIAMOND HEAD CRATER PRIOR TO THIS EARTHCACHE BEING PUBLISHED, YOUR VISIT WILL NOT COUNT AS HAVING COMPLETED THE LOGGING REQUIREMENTS FOR CLAIMING THIS EARTHCACHE AND YOUR LOG WILL BE DELETED. THANK YOU FOR YOUR COOPERATION!!
Additional Hints
(Decrypt)
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