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Waimangu (Black Water) Volcanic Valley is the site of both the largest geyser and the largest hot spring ever observed, and of the Pink and White Terraces, once called the southern eighth wonder of the world. It is located around 26 km (16 miles) south of Rotorua. This magical place has been completely reshaped by the violent eruption of Mount Tarawera on 10th June 1886, when a line of craters opened and formed the Tarawera Rift, running from Tarawera through Lake Rotomahana up the Waimangu Valley. Thus, the current setting is the youngest of New Zealands geothermal areas and one of the most active. While prior to the volcanic eruption geothermal features were focused on the at that time substantially smaller and shallower Lake Rotomahana and its shore areas, several years afterwards geysers, hot springs, craters, and sinter terraces spread all along the newly formed rift valley. Okataina Volcanic Centre is believed to provide the heatsource for the Waimangu hydrothermal system.
Just behind the entrance at the visitor centre people enjoy a wonderful view over the valley, including Frying Pan Lake in foreground, Inferno Crater behind it on the righthand side and Mount Tarawera in the background right.
Before the trail descends to Frying Pan lake, on the righthand side a view onto Emerald Pool opens up. It covers the bottom of the 50 m (160 feet) deep Southern Crater, which was created by the 1886 Mount Tarawera eruption as many further craters in the valley. Emerald Pool is a cold waterbody filled with rainwater.
Further down, the trail offers a series of observation possibilities for Frying Pan Lake. The lake occupies Echo Crater, named for the echo effect which is strongest at the southern shoreline. Unlike many other crater structures in Waimangu, in its present shape Echo Crater is only partially a result of the Tarawera eruption. A later, three days lasting hydrothermal eruption bursted its western section open on 1st April 1917. Unfortunately, two people died in the incident. After the eruption several hot springs on the bottom of the crater formed Frying Pan Lake. With an extension of 38,000 m2 (410,000 square feet) it is the world's largest hot spring. The 55 °C (131 °F) warm water is slightly acidic (pH 3.5) and reaches a maximum depth of 20.9 m (68.5 feet) at an average of 6 m (20 feet).
Not only on the bottom of Frying Pan Lake but also along its shoreline several hot springs, some fumaroles and even one geyser are located. Starting in the southwest as a visitor will encounter it on location, an unnamed, colourful terrace consisting of siliceous sinter grows into the lake. In a sense it can be regarded as the last remnant of the famous Trinity Terrace, even though latter was situated a little bit farther east on the shore. On 22nd February 1973, a vigorous hydrothermal eruption destroyed Trinity Terrace completely.
East of the former Trinity Terrace and just opposite the Cathedral Rocks, the southeast shore of Frying Pan Lake hosts the geyser Taha Roto (Lakeside Geyser). It used to erupt every few minutes up to 3 m (10 feet) high. During our visits on 17th and 18th November 2019, Taha Roto was not playing, so I was not able to document its location by a photo. Ashley D. Cody listed the geyser as active in his 2007 report Geodiversity of geothermal fields in the Taupo Volcanic Zone, and the youngest hint to Taha Roto's activity I could find so far was a blog entry by a visitor from autumn 2013.
The trail continues to a viewpoint face-to-face with Cathedral Rocks. This steaming monolith consists of solidified lava and is at least 60,000 years old. The lake in front of Catheral Rocks shows bubbling and upwelling from springs at its bottom, which are known as Cathedral Rock mud pools.
From the same viewpoint a look in eastern direction reveals the site of Waimangu Geyser. However, if not an information board would help to visualise the former setting, little would indicate that the overgrown area northeast of Frying Pan Lake once hosted the crater of the largest geyser ever known. Waimangu Geyser was active from 1900 to 1904 and erupted from a lake measuring 80 x 130 m (262 x 426 feet). Current visitors may not be aware that the modern trail partly runs through the former crater lake of Waimangu Geyser. At an interval around 36 hours it usually shot out water 100-400 m (330-1300 feet) high, whereby the largest ever reported eruption was stated with 450 m (1476 feet). The name Waimangu (Black Water) came from the observation that its eruption columns were dark coloured by entrained soil and rocks. Although only active for a brief period of time, on 30th August 1903 the gigantic geyser killed four visitors, including New Zealands rugby star and Waimangu tourist guide Joseph Warbrick. The group was standing close to the edge of the geyser when an unexpected eruption swept them away and the boiling water scalded them to death. A white cross on the lowest point of the crater rim to the east still marks the position of the accident.
Another fatal incident was reported by James W. Alexandre in The Ruapehu Crater Lake, Journal of the Royal Astronomical Society of Canada, Vol. XXV, No. 10, p. 427, 1931. According to Alexandre, Waimangu Geyser was already regarded as extinct, but after many years of quietness it erupted unexpectedly and threw "boiling mud and incandescent boulders [on the caretakers residence at some distance to the crater] which overwhelmed the house and set it alight". During this incident Mrs. Warbrick, the wife of the caretaker, was seriously wounded, but she sheltered her baby with her remaining clothing and dragged herself to Rotorua to meet her husband. Once arrived there, she died in a hospital but succeeded in rescuing her baby.
However, Alexandre's story features so many contradictions and improbabilities that it can only be fiction. Neither is an eruption known many years after Waimangu Geyser entered dormancy nor has the geyser ever ejected incandescent boulders nor were buildings ever located so close to the geyser that emissions could reach them. The heartbreaking tenor of a story which was apparently never published in newspapers is an additional indication for a rumour. It seems that here motifs from the Tarawera eruption in 1886 were mixed with motifs from the Warbrick accident by Waimangu Geyser to form a spectacular new story.
The water of Frying Pan Lake discharges to the northeast. Within the shallow outlet of the lake a good number of tiny springs, which may or may not be members of the Cathedral Rock mud pools, deposit siliceous sinter, coloured by traces of toxic heavy metals such as antimony, arsenic, molybdenum, and tungsten. In its further course the outlet is called Hot Water Creek, or, depending on the view taken, already Waimangu Stream. Other authors don't call the creek Waimangu Stream until it has joined with Haumi Stream near Puara Spring.
Downstream the Hot Water Creek two clusters of small hot springs deserve particular attention. First, a couple of springs perforate a sinter shield or terrace on the near side of the creek. They are called Nga Puia o te Papa (The Geysers of Mother Earth) and include at least ten perpetually spouting springs. T. Scott Bryan assumed that "several of the many vents among the Nga Puia O Te Papa complex could be geysers" (GOSA Transactions V, 1994). I observed the features for about one hour but could find no evidence for geyser activity, what does not mean that it never happens.
Nevertheless, one of the spouters close to the trail displays a beautifully agate-like banded geyserite deposit.
Another one has formed a raised, horseshoe-like rim.
The one next to the creek featured the strongest eruptions.
The second group of hot springs along the creek carries the name Te Ara Mokoroa (Long Abiding Path of Knowledge). When in May 1975 "N Spring" sprang to life, scientists nourished vague hopes that it could be a new life sign of the old Waimangu Geyser, whose lake formerly covered this spot. As we know today, their hopes for larger events to come were disappointed because everything that happened was the development of a few even smaller satellite springs. Apparently, the associated mental experience led to the philosophically sounding name of the cluster.
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