Structural Control and Origin of Volcanism in the Taupo Volcanic Zone


Volcano Ruapehu is the highest mountain on the North Island and it is actually the latest volcano that has been erupted. It is located at the southernmost part of the North Island that stands 2797 meters or 9175 feet tall. Mount Ruapehu can be found at the Southern end of the Taupo Volcanic Zone, which is a segment that expands through the crust of the planet Earth, and indeed, it has been the cause of the eruptions over the long period of time for about two million years.

Another thing is, because the central axis of the Taupo Volcanic Zone, it has given way on the major active faults that arouse to the east and west as well of the mount Ruapehu that is actually drove the down part of the volcano to become feeble. And the slipups that were marked by the boundary of the Taupo volcanic zone in the location of the mount Ruapehu causes damage to the top most part of the volcano and the measure of the fault is exactly 20 kilometers south of it (Charlier, 2005).

Basically, mount ruapehu is composed of the volcanic rock, which is called as andesite. The andesite lava goes with the fragmental rubble radiate from the top region that forms a stratovolcano and it rises from the lowlands that surround the volcano for about 2000 meters. Being a stratovolcano, they are precipitous and have a tendency to fall down generating fragments of landslides and lahars that stretch outwards on the lowlands that surround the volcano.

Claiming the power on the area of the summit is seen to be a crater lake that has approximately eight up to ten million milliliters of acid waters when it overflows. In the years 1945 and 1995, which was during the historical eruptions, the water in the lake has been thrown out of the crater and into the glaciers that surround it and into the catchments of Whangaehu. The dislodgment of the water in the lake causes some eruptions on the volcano and it produces ashes that may cause lahars if it gets more crucial.

Actually, when the time that the water goes into the crater at the summit, wet eruptions or also known as phreatomagmatic eruptions comes into the action with matching water eviction that will then results to lahars and tangential gushes. The lahars from it may cause damage to a lot of affected areas that it will affect and maybe one of the big cause of death in the countries that are closely located at the volcano ruapehu especially those in the Pacific regions and one example is the New Zealand (Cole, 1979).


As the highest volcano in the North Island of New Zealand, Mt. Ruapehu stands at 2797 meters. It will be found at the southern borderline of the Taupo Volcanic Zone, a zone of eased with a 15 kilometer thick and stretches 8–10 millimeters per year of continental crust illustrated by an extraordinarily superior heat flow of 700 mW/m2, and elevated by a 3He instability. This Taupo Volcanic Zone has become one of the most productive and lively silicic magmatic systems on Earth that are from 15,000 and 20,000 km3 of emerging rhyolitic substance that erupted over the past years of about two million (De Paulo, 1989).

Knowing the latest eruptions that occurred in 1995 and 1996, mount Ruapehu has been active over a long period for about 200 thousand. It is said that mount ruapehu has four major formations of flow unit and mostly, they have now been dated by the Ar/Ar technique. The Ruapehu volcanic rock varies in work from the basaltic andesite to dacite with the large majority of it being andesite, indeed. A good example was discovered and it is a typical Ruapehu andesite that has phenocrysts of plagioclase, orthopyroxene, clinopyroxene, and some magnetite in glasslike as or maybe a fine crystal groundmass that is conquered by plagioclase and pyroxene. The Amphibole phenocrysts are actually tremendously extraordinary.

Mount ruapehu mainly consists of andesite and started erupting at approximately 250,000 years ago. In history, the major volcanic eruptions have been said to be 50 years gap from the time it has erupted, such instances like 1895 and then 1945, 1995 to 1996 as well. Small eruptions always occur for at least sixty times since the year 1945. In 1970s, some small eruptions brought some related damages to the ski fields (Gamble et al., 1997).

Along with the big eruptions that happened in mount Ruapehu, there formed a warm acidic crater lake which has a melting snow. These major reactions could affect the expulsion of the water in the lake. Where a major outbreak has set down a tephra barrier across the outlet of the lake, the barrier may fall down when the lake has restocked and risen on top of the level of its regular outlet and then there came the outrush of water which may result to huge lahars. But somehow in the year 2000, the ERLAWS system was set up on the mountain to perceive such a fall down and give warning to the necessary people or events that may undergo (Arculus et al., 1986).

Volcanic Activities

The eruption happened in 1945 unfilled the Crater Lake and barrier the outlet of the volcano with tephra. The Crater Lake apparently restocked with water and broke down in anticipation of on the 24th of December, 1953 and the dam of the tephra broke down actually that resulted to the flow of lahars in the Whangaehu River.

The Tangiwai catastrophe caused the death of 151 lives when the Tangiwai railway bridge transversed the Whangaehu River distorted at the same time as the lahar was flowing out rapidly at the exact moment that a train crossed the bridge (Gamble et al., 1997). It was said that the bridge was not yet done concretely and that is one of the reasons why the railway has collapsed easily when the lahar has flown out from the volcano. The driver of the train did the necessary things to stop the train but it has failed and six of the carriages were gone out of the train.

In the years 1995 up to 1996, some amazing eruptions took place in mount Ruapehu. Actually, the volcano had been viewing signs of increased commotion since November 1994, and these signs were with superior Crater Lake temperatures and a sequence of eruptions that increased in concentration over for about nine months. Several lahars were viewed, both in the Whangaehu River and also on the other areas of the volcano and that was between September 18 and September 25, 1995, which indicates the Crater Lake was being unfilled by such eruptions.

The Department of Conservation right away issued danger cautions and gave advice to the people to avoid going near into the mountain, therefore it ended the season of ski. The eruption cloud interrupts air voyages sometimes it causes the airports to be closed in the central North Island airspace. Some periodic eruptions sustained until the end of November 1995 (Gamble et al., 1997). During the hours of such major eruptions occurred in the night which was being reported on September 25, 1995, the news media were demanding to get videos of the live eruption and proletarian photographers had actually published those images of eruption on the World Wide Web.

Another minor eruption chapter began on the morning of the 17th of June 1996. Mount Ruapehu was closed to the public or the skiers at that time and that was the first time that they did that. After the eruption in 1996 it was documented that a disastrous lahar could once more occur when the time the Crater Lake disintegrates the volcanic ash dam overcrowding the outlet of the lake. This is the same system that caused the overflowing of lahar in 1953.

The lake slowly but surely packed with snowmelt and had attained the level of the tough rock border on the first month of 2005. However, the lahar finally came in on the 18th of March 2007. The 2006 eruption of mount Ruapehu happened at 10.30pm on the 4th of October 2006. The small eruption shaped a volcanic earthquake with a magnitude 2.8 which sent a water plume of 200 meters into the air and a 6-meter wave that smashed into the wall of the crater.

In the eruption of 2007, at about 8:20pm on 25 September 2007 there occurred a hydrothermal eruption without initial warnings. As a result to that, it was said that a 22 year old primary school teacher had experienced a tragedy when he got his leg crashed and the rescuers got a hard time saving him on the Dome Shelter which was near the crater. The eruption was with an earthquake which was about 7 minutes long and tagged 2.9 levels of intensity on the Richter scale (Gamble et al., 1997).


Mount Ruapehu is an active volcano and anytime it could form hazardous materials that it may blow off from its crater which may possibly cause death to the lives of the people who appear to be adjacent to the volcano. With that in mind, just on the recent date which was on the second of May, 2008, there was a warning declared after the scientists of GNS who observes the lake of the volcano on a level one of its eruption or a preliminary sign of irregularities in the volcano.

These activities comprise of chemical changes, some gases and irregular temperature that may be harmful as a first sign of the volcanic activities for a volcano-like mount Ruapehu. The warning was worn to inform and educate the visitors to be aware and know the possibility of experiencing an explosion which may be higher than the typical ones that it had in the past and this observable fact could take place any time and this could be the continuation of the eruption that happened last year in 2007.


Arculus, R.J and Powell, R. Source component mixing in regions of arc magma generation, Journal of Geophysical Research 91 (1986), pp. 5913–5926.

Charlier, B.L.A., Wilson, C.J.N., Lowenstern, J.B., Blake, S., Van Calsteren, P.W., and Davidson, J.P., Magma generation at a large, hyperactive silicic volcano (Taupo, New Zealand) revealed by U–Th and U–Pb systematics in zircons, Journal of Petrology 46 (2005), pp. 3–32.

Cole, J.W. Structural control and origin of volcanism in the Taupo volcanic zone, New Zealand, New Zealand Journal of Geology and Geophysics 22 (1979), pp. 631–657.

De Paolo, D.J. Trace element and isotopic effects of combined wall rock assimilation and fractional crystallisation, Earth and Planetary Science Letters 53 (1981), pp. 189–202.

Gamble, J.A., Wood, C.P., Price, R.C., Waight, T., Smith I.E.M. and Nagakawa, M. Major, trace element and isotope geochemistry of Historic (1945–1996) eruptions of Ruapehu Volcano, New Zealand. State of the Arc ’97, Island arc magma genesis workshop, Adelaide, Australia, Abstracts of the Geological Society of Australia 45 (1997), pp. 27–29.

Graham, I.J., Blattner P., and McCulloch, M.T. Meta-igneous granulite xenoliths from Mount Ruapehu , New Zealand : fragments of altered oceanic crust?, Contributions to Mineralogy and Petrology 105 (1990), pp. 650–661.

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