Champagne Pool, approximately 60 m in diameter and 62 m deep, is the largest hot water spring at the Wai-O-Tapu geothermal area in the Waikato region of the North Island of New Zealand. Wai-O-Tapu is located right on the edge of one of the four volcanic calderas within the Taupo Volcanic Zone, one of the world’s most active volcanic areas in the world. Champagne Pool occupies a 700 year old explosion crater formed by a hydrothermal eruption. The pumice material around the pool was also ejected by that eruption. Water enters the pool at about 72°C with a pH of 5.4. The surface temperature of the water in Champagne Pool is 74 °C and bubbles of carbon dioxide can be observed rising to the surface, giving the pool its famous name. As the water flows over the Artist’s Palette towards the Sinter Terraces, the temperatre drops to appromimately 15°C and the pH increases to 7.6. Minerals present in the water of Champagne Pool consist of gold, silver, mercury, sulphur, arsenic, thallium, and antimony which are deposited in the surrounding sinter ledge. The various sinter ledges have been associated with the tilting of the pool as a consequence of earthquake activity.
The orange, green/yellow, and grey colors in the Champagne Pool are the result of antimony oxide, colloidal sulphur/ ferrous iron, and sulphurous mud respectively. The orange-colored edge of the Champagne Pool contains arsenic and antimony sulphur compounds that are rich in minerals including gold and silver. The water overflowing the Champagne Pool is rich in silica, and as the water cools, progressively more silica precipitates and forms into a sinter. The Primrose Terraces have been forming for 700 years and are the largest in the southern hemisphere covering 1.2 ha (approximately 3 acres) since the destruction of the Pink and White Terraces with the eruption of Mt. Tarawera in 1886.
Huku Falls, North Island, NZ
The Huku Falls are natural waterfalls that are located close to Lake Taupo on the North Island of New Zealand and are the result of volcanic activity. Although these falls are not very high, the color of the water is a very unique shade of blue that is the result of very clear water reflecting blue light. The volume of water pasing over the falls varies between 32-270 m3/ sec. At the base of the falls is a dangerous undertow caused by the falling water plunging deep into the pool. Water temperature varies from 22°C in the summer to 10.5°C in the winter. The average daily flows over Huka Falls is 160 m3/ sec. The Waikato River (100 m wide and 4 m deep) is forced into a channel 15 m wide and 10 m deep upstream. The level of the River is controlled by Lake Taupo’s control gate bridge.
The pounding of water at the base of the waterfall is a powerful force for erosion. Even at the lip of the waterfall, the water gains extra erosive power as it accelerates when approaching the brink. Therefore, waterfalls are ephemeral phenomena, geologically speaking. While the surging water tears away at the base of the falls and removes its rock foundations, the scouring of the lip grinds back the brink of the falls and decreases its overall height. In geologic terms, waterfalls are quite temporary, and their presence is a sign of the unique geologic conditions that produced them.
Creation of Huku Falls:
An ancient lake once covered most of what is today the Waikato River Valley. Eventually, the lake drained and the Waikato River eroded through soft mudstone and pumice until it struck a layer hardened by silica from much earlier geothermal activity. Unable to erode this later, the river became confined to joints and fissures in the rock. Over the centuries, the river cut a deep narrow channel into this hard layer until it reached a soft underlying layer which collapses, creating the steep-side basin and the falls where the river plunges over the lip into the basin. Today the river continues this erosion process and the Huku Falls move upstream.
Rivers begin re-grading their courses and establishing a new curve of water erosion. Where the latter curve meets the former curve, there is a break in the slope of the river, called the knick point. The knick point usually forms a fall line over which descend the tributaries to the main stream.
The Waikato River System is the most highly developed for electicity generation in New Zealand. It supplies 8 hydroelectic stations and provides cooling water for 2 geothermal and 1 thermal stations. The 11 stations on Waikato produce 65% of the North Island/s power generation and approximately 25% of New Zealand’s hydropower, which constitutes 15% of New Zealand’s total power.
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