Tongariro

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  • 39.157°S
  • 175.632°E

  • 1978 m
    6488 ft

  • 241080
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Most Recent Weekly Report: 27 March-2 April 2013


On 25 March GeoNet reported that Tongariro remained quiet with no eruptive activity being detected since the explosion on 21 November 2012. Steam-and-gas plumes rose from the Te Maari Craters. The Aviation Colour Code was lowered to Green (second lowest on a 4 four-color scale) and the Volcanic Alert Level remained at 1 (on a scale of 0-5).

Source: New Zealand GeoNet Project


Most Recent Bulletin Report: July 2012 (BGVN 37:07)


Seismicity preceded phreatic explosion; associated rainfall-fed lahar

Elevated seismicity in July 2012 preceded a phreatic eruption at Tongariro on 6 August. The eruption ejected blocks of old lava from the crater area, and triggered a debris flow down a drainage on a flank of the volcano. Six days later, heavy rainfall remobilized some of the debris flow and generated a small flood/lahar that crossed a state highway. This report summarizes GeoNet alert bulletins and Taupo Civil Defense postings concerning the phreatic explosion and associated events (through 17 August 2012).

Precursory seismicity. GeoNet reported elevated numbers of volcanic earthquakes (M < 2.5) beginning on 13 July (figure 2). Seismicity then declined until 18 July, when volcanic earthquakes returned, increasing in magnitude and abundance through 20 July. The earthquakes were clustered between Emerald Lake and the SE shore of Lake Rotoaira at 2-7 km depth; a subset of the earthquakes were tightly clustered between Blue Lake and Te Maari (Te Mari) Craters within the same depth range (figures 2 and 3). As a result, the Volcano Alert Level was raised from 0 to 1 (on a scale from 0-5) and the Avation Colour Code was raised from Green to Yellow (on a four color scale; Green-Yellow-Orange-Red) on 20 July.

Figure 2. Seismicity at Tongariro during 11 July-6 August 2012, leading up to a phreatic eruption at 2350 on 6 August. Shown are the number of seismic events per day (107 in total, top panel), the depth at which each event occurred (and associated error bars, middle panel), and the magnitude of each event (bottom panel). Courtesy of GeoNet.
Figure 3. Mapped epicenters of seismic events recorded at Tongariro during 25 May-23 August 2012. A phreatic eruption occurred late on 6 August (see figure 2). During the precursory activity (late July and early August), seismicity concentrated between Emerald Lake (E) and Lake Rotoaira (R), with a cluster between Blue Lake (B) and Te Maari Craters (T). Courtesy of GeoNet.

By 23 July, GeoNet had deployed four portable seismometers and had sampled springs and fumaroles. They reported that provisional analyses of gas samples indicated a marked increase in volcanic gases above typical mixtures of hydrothermal and volcanic gas signatures (see subsection “Ash and gas analyses” for detail). By 31 July, GeoNet had also installed a GPS instrument to monitor any deformation.

Phreatic eruption. At 2352 on 6 August, a phreatic eruption occurred from a vent located within the Te Maari Craters area. An explosion generated seismic signals that lasted a few minutes, followed by a series of discrete small earthquakes during the next few tens of minutes. Within 35 minutes, GeoNet posted an Alert Bulletin announcing that ashfall had been reported; the Volcano Alert Level was raised to 2 and the Aviation Colour Code was raised to Red. Taupo Civil Defense responded by closing State Highways 1 and 46 (to the E and N of Tongariro, respectively).

Approximately one hour after the eruption, the Cooperative Institute for Meteorological Satellite Studies (CIMSS) observed in satellite imagery that an ash plume was drifting more than 50 km E from Tongariro (figure 4). They also reported that airports had cancelled flights at Gisborne (210 km ENE), Rotorua (120 km NNE), Taupo (60 km NE), and Palmerston North (135 km S).

Figure 4. A Visible Infrared Imaging Radiometer Suite (VIIRS) image acquired by the Suomi National Polar-orbiting Partnership (NPP) satellite at 1252 UTC on 6 August 2012 (0052 NZST on 7 August) showing an ash plume drifting more than 50 km E from Tongariro, after the phreatic explosion ~1 hour earlier. The windward end of the plume remains over the volcano, implying ongoing emissions. In the main image, the North Island of New Zealand is outlined in teal, and Rotorua is labeled to the N of the plume. In both images, the ash plume is labeled in yellow, and Tongariro is labeled in red, just W of the plume. Courtesy of CIMSS.

GeoNet reported that no volcanic tremor occurred before or after the event, and the Aviation Colour Code was reduced to Orange ~12 hours later (about 1200 on 7 August), and reduced again the next day (1500 on 8 August).

GeoNet conducted an observation flight on 8 August and photographed a variety of features discussed and illustrated in more detail below. They included: (1) a new vent area residing in a small crater, and associated steaming fissures, (2) a debris flow, and (3) impact craters.

The new vent(s) are located in the Upper Te Maari Craters area (figure 5a); low clouds prevented scientists from viewing areas higher than the lowest parts of Upper Te Maari Crater. Photographs of the area revealed a nearby steaming eruptive fissure, and more intense steaming in areas of ground that had been steaming prior to the eruption (figure 5b).

Figure 5. Photographs taken after Tongariro’s 6 August 2012 phreatic eruption showing the Upper Te Maari vent area. In (A) the view is looking SE towards Upper Te Maari crater, with areas of fumaroles and a new vent on the outer edge of the crater (indicated by the arrow). (B) is looking NW showing vents along a fissure around the S side of Upper Te Maari crater. Upper Te Maari crater is indicated in each photo with the '*' symbol. Both photographs were taken during a morning observation flight on 8 August 2012. Courtesy of GeoNet.

A debris flow generated by the phreatic eruption comprised rock and soil debris that blocked a stream valley draining NW from the Te Maari Craters area (figure 6). GeoNet reported water ponding around the edges, and ash that had been remobilized into slurry flows. GeoNet noted that areas of the debris flow (especially in the upper sections) had eroded into the substrate (figure 6a).

Figure 6. Upper (A) and lower (B) portions of the debris flow generated by the 6 August 2012 phreatic eruption at Tongariro. The debris flow extended down a stream valley draining NW from the Te Maari Craters (steaming areas visible in the top-most portion of (A)). White asterisks in both photos indicate regions where the debris flow eroded into the substrate. White arrows in (B) indicate areas of newly ponded water at the edges of the flow. Courtesy of GeoNet.

The explosion ejected blocks of lava up to 2 km from the Te Maari Craters area, leaving impact craters in vegetation and ground surfaces (figure 7). All blocks were angular, and none were steaming or surrounded by burnt vegetation; GeoNet thus concluded that the blocks comprised old (non-juvenile) lava(s) ejected from the vent area.

Figure 7. Blocks of lava ejected up to 2 km from the Te Maari Craters area during the phreatic explosion on 6 August 2012 left impact craters in vegetation and ground surfaces (circled). Courtesy of GeoNet.

Ash and gas analyses. Textural analyses indicated that the ash emitted during the 6 August explosion contained little-to-no fresh (juvenile) lava, suggesting that the eruption was primarily steam driven (phreatic). GeoNet also reported that analysis of the fluorine content of the ash indicated that, except in the immediate vicinity of the volcano, there were little health or agricultural concerns.

For 9 August, GeoNet reported emissions of 2,100 tons/day of SO2, 3,900 tons/day of CO2, and 364 tons/day of H2S from vents. Sulfur (H2S) smells were reported in downwind locations during 11-12 August, and further reports were filed from the Manawatu region on 15 August. GeoNet attributed the sulfur odors to “passive degassing of magma beneath the surface of Tongariro.”

Heavy rains spawn minor lahar. In concert with the 11 August release of a new, updated hazard map of Tongariro (figure 8), GeoNet warned motorists not to stop their vehicles along Highway 46 (N of Tongariro) due to hazards in that area. Following heavy rains the next morning, a minor flood/lahar crossed State Highway 46 near the S tip of Lake Rotoaira (at a location ~6 km W of Rangipo). According to the New Zealand Herald, a driver described 13-cm-deep mud crossing the road at 0830 that day. Scientists at GNS Science stressed that the lahar was not a direct result of an eruptive process, and a resident reported that the area was commonly washed out during heavy rains.

Figure 8. The updated hazard map released by GeoNet on 11 August 2012, which includes the 6 August vents seen in Tongariro’s Te Maari Craters area (dashed black circle). As seen in the legend, the map indicates the locations prone to pyroclastic flows and mudflows (shaded yellow) and an area within a 3 km radius of the summit that is prone to gas hazards and flying rocks (shaded orange). Where the two zones overlap, the map is shaded red. Red dots indicate eruptive vents active in the last 27,000 years. Orange triangular “hut” icons indicate nearby mountain refuges. The larger poster conveys extensive hazard information. Note disclaimer (upper left) and wide range of agency collaboration (lower right) in map production. The highest peak of the complex is at Ngauruhoe (near the SW corner of the map). As stated in the comment in the SW corner of the map, “Tongariro and Ngauruhoe are parts of one active volcanic system.” Courtesy of GeoNet.

Ten days after the phreatic explosion, GeoNet reduced the Volcano Alert Level to 1, stating that minor eruptive activity, required for Volcanic Alert Level 2, had ceased. The Aviation Colour Code remained at Yellow as of 24 August 2012.

Information Contacts: GeoNet, a collaboration between the Earthquake Commission and GNS Science (URL: http://www.geonet.org.nz/); GNS Science, Wairakei Research Center, Private Bag 2000, Taupo 3352, New Zealand (URL: http://www.gns.cri.nz/); Earthquake Commission (EQC), PO Box 790, Wellington, New Zealand (URL: http://www.eqc.govt.nz/); The Cooperative Institute for Meteorological Satellite Studes (CIMSS), a collaboration between the University of Wisonsin-Madison, the National Oceanic and Atmospheric Administration, and the National Aeronautics and Space Administration, Space Science and Engineering Center, 1225 W. Dayton St., Madison, WI 53706 (URL: http://cimss.ssec.wisc.edu/); University of Wisconsin-Madison (UW-Madison) (URL: http://www.wisc.edu/); National Oceanic and Atmospheric Administration (NOAA) (URL: http://www.noaa.gov/about-noaa.html); National Aeronautics and Space Administration (NASA) (URL: http://www.nasa.gov/); New Zealand Herald (URL: http://www.nzherald.co.nz/).

Index of Weekly Reports


2013: February | March
2012: July | August | September | October | November
2008: December
2006: June | November

Weekly Reports


27 March-2 April 2013

On 25 March GeoNet reported that Tongariro remained quiet with no eruptive activity being detected since the explosion on 21 November 2012. Steam-and-gas plumes rose from the Te Maari Craters. The Aviation Colour Code was lowered to Green (second lowest on a 4 four-color scale) and the Volcanic Alert Level remained at 1 (on a scale of 0-5).

Source: New Zealand GeoNet Project


13 February-19 February 2013

On 14 February GeoNet reported that Tongariro remained quiet with no eruptive activity being detected since the explosion on 21 November 2012. Steam-and-gas plumes rose from the Te Maari Craters, and were unusually strong during the recent weeks possibly due to weather conditions. The Aviation Colour Code remained at Yellow (second lowest on a 4 four-color scale) and the Volcanic Alert Level remained at 1 (on a scale of 0-5).

Source: New Zealand GeoNet Project


21 November-27 November 2012

A small eruption at Tongariro's Te Maari Craters occurred at 1325 on 21 November, without precursory events, prompting GeoNet to raise the Volcanic Alert Level to 2 and the Aviation Colour Code to Red. A report at 1730 noted that the eruption appeared to be over; the Aviation Colour Code was lowered to Orange.

The eruption occurred in the same area as the previous eruption on 6 August and lasted less than five minutes, although local seismic activity lasted about 15 minutes. GNS staff and hikers saw the eruption. An ash plume rose 3-4 km above the Upper Te Maari crater and produced ashfall across part of State Highway 46 and NE towards Turangi (21 km NE). Two small pyroclastic density currents were produced at the base of the column, to the W and N of the crater, and traveled a limited distance of a few hundred meters downslope. Later that afternoon gas-and-steam plumes drifted SE. On 22 November a sulfur gas odor was reported in Manawatu (S) and Hawke's Bay (115 km ESE), downwind of Tongariro. A substantial amount of gas was emitted during 22-23 November. The Aviation Colour Code was lowered to Yellow on 23 November due to the absence of emitted ash. On 26 November GeoNet noted that no further volcanic activity had occurred since the eruption, gas flux had decreased, and seismic activity remained low.

Source: New Zealand GeoNet Project


7 November-13 November 2012

On 5 November, GeoNet reported that several teams of scientists had been visiting Tongariro's Te Mari Craters to service portable seismometers (complementing four permanent installations), sample gas vents, and collect samples of ejecta. The report noted that not many earthquakes had been recorded recently, and that the hottest gas vent was 235 degrees Celsius while the others ranged from 95-104 degrees. On 30 October the sulfur dioxide flux was 154 tonnes per day and the carbon dioxide flux was 477 tonnes per day. The volcano continued to actively degas. The Aviation Colour Code remained at Yellow and the Volcanic Alert Level remained at 1 (signs of volcano unrest).

Source: New Zealand GeoNet Project


10 October-16 October 2012

On 12 October, the GeoNet Data Centre reported that Tongariro had been degassing after the 6 August eruption from the Te Mari Craters. Gas plumes drifted downwind and were detected a hundred kilometers or more away. During the previous two weeks an odor was noticed in Manawatu (112 km S) and Hawke's Bay (120 km ESE).

Source: New Zealand GeoNet Project


26 September-2 October 2012

The GeoNet Data Centre reported that researchers visited Tongariro's Upper Te Mari Craters on 30 September to sample several of the fumaroles, conduct a carbon dioxide soil gas survey, collect ejecta from the 6-7 August eruption, and photograph the area. They found that the average carbon dioxide soil gas flux was lower than the 27 July measurements; 24 sites had increased fluxes while 20 had decreased. The estimated soil gas emission has decreased from about 5.8 to 2.5 tonnes per day based on these measurements.

Source: New Zealand GeoNet Project


15 August-21 August 2012

GeoNet reported that seismic activity at Tongariro remained low during 14-16 August; weather conditions prevented observations of the craters. There were several reports of gas odors on 15 August, particularly from the Manawatu region (S). On 17 August GeoNet noted that although very minor amounts of ash were emitted in the first few days after the eruption, there had been no significant activity since 6 August. Seismic activity had returned to low levels after the eruption. The Alert Level was lowered to 1 (on a scale of 0-5) and the Aviation Colour Code remained at Yellow (second lowest on a four-color scale).

Source: New Zealand GeoNet Project


8 August-14 August 2012

GeoNet reported that favorable weather allowed GNS Science and Department of Conservation scientists to conduct an observation flight over Tongariro on 8 August. They noted actively steaming vents that were visible at a new crater area formed on 6 August below the Upper Te Mari crater, but low clouds prevented any views above this elevation. Blocks of old and hydrothermally altered lava, as large as 1 m in diameter, ejected by the eruption fell 1.5-2 km from the Te Mari craters area. Falling blocks formed impact craters in the ground in an extensive area to the E and W of the new vents. Most blocks were covered by grey ash but many on the W slopes were not, suggesting that they were ejected after the main ash-producing phase of the eruption.

The scientists also noted that previously steaming ground at Ketetahi and Lower Te Mari crater appeared more vigorous, but there were no obvious major changes. A debris flow generated by the eruption partly filled a stream valley draining N-W from the Upper Te Mari crater area. The deposit had blocked some stream tributaries but most water diverted around the edges. Ash had slumped from the banks into the stream valley, and in other stream valleys ash has been re-mobilized in slurry flows. No lahars were generated by the eruption.

New rock falls were visible around the walls of the new vent area and Lower Te Mari craters and in some stream valley walls near the craters. This suggested that significant ground shaking took place during the eruption. The Alert Level remained at 2 (on a scale of 0-5) and the Aviation Colour Code was lowered to Yellow (second lowest on a four-color scale).

During 8-9 August seismic activity remained at a low level; only a few small events were recorded. Preliminary analysis of the ash showed that there was little to no new magma erupted. Gas analysis on 9 August revealed emissions around 2,100 tonnes per day of sulfur dioxide, 3,900 tonnes per day of carbon dioxide, and 364 tonnes per day of hydrogen sulfide, confirming the presence of magma below the volcano. During an overflight on 9 August scientists observed minor ash emissions from the vents. Seismicity continued to remain low during 10-14 August. Heavy rains on 12 August caused a lahar to cross State Highway 46, approximately 6 km W of Rangipo.

Source: New Zealand GeoNet Project


1 August-7 August 2012

On 6 August GeoNet reported that volcanic earthquakes continued beneath Tongariro but the size and number had decreased; there were fewer than five events each day. At about 2350 a short-lived (~1-2 minutes) phreatic eruption occurred at the Te Mari craters area, followed by a series of discrete small earthquakes over the next few tens of minutes. The Alert Level was raised to 2 (on a scale of 0-5) and the Aviation Colour Code was raised to Orange (second highest on a four-color scale). An ash plume drifted E and ashfall was reported in areas around the volcano. According to a news article, a GNS Science volcanologist noted that there were reports of "red hot rocks being thrown out of the crater", explosions, and lighting. The article also stated that some people in the Tongariro area had self-evacuated following the eruption. The Desert Road section of State Highway 1 (NE) had been closed due to poor visibility from the ash, and about 5 cm of ash had fallen on State Highway 46, to the N. Some flights to and from Gisborne (210 km ENE), Rotorua (120 NNE), Taupo (60 km NE), and Palmerston North (135 km S) were delayed or cancelled due to the eruption, and Hawke's Bay Airport (110 km ESE) had closed. GeoNet observed that no volcanic tremor occurred in the days preceding the eruption. The last eruption occurred in 1897. [Correction: The last eruption from the Te Mari craters area had occurred in 1896.]

On 7 August white steam clouds rose from the Te Mari craters area but poor weather conditions at the time obscured a direct view of the active vent(s). A few small earthquakes had been detected. A news article stated that alpine guides observed three active vents that appeared to be new.

Sources: Stuff; New Zealand GeoNet Project


25 July-31 July 2012

On 31 July GeoNet reported that seismicity at Tongariro had declined the previous week but increased again during 28-29 July, and as of 31 July, between 3 and 10 events were being recorded daily. The earthquakes were clustered in a zone between Tongariro and the E side of Lake Rotoaira, at 2-7 km depth. The Alert Level remained at 1 (on a scale of 0-5) and the Aviation Colour Code remained at Yellow (on a four-color scale).

Source: New Zealand GeoNet Project


18 July-24 July 2012

A sequence of small volcanic earthquakes beneath Tongariro was detected by a few of the seismometers in the permanent network. Earthquakes with magnitudes less than 2.5 were clustered between Emerald Crater (E of the summit) and the Te Mari craters (2 km E east of Ketetahi hot springs on the N flank) at 2-7 km depth. The sequence started on 13 July, soon declined, and then again increased during 18-20 July. The Alert Level was raised to 1 (on a scale of 0-5) and the Aviation Colour Code was raised to Yellow (on a four-color scale) on 20 July.

In response to the increased seismicity, GeoNet installed four portable seismographs and conducted gas and spring sampling. During 21-22 July seismicity declined; one event was detected on 23 July. Provisional analysis of the gas samples collected during 21-22 July indicated a marked increase in the volcanic gas component of the typical mix of volcanic and hydrothermal gases. Residents reported a gas odor.

Source: New Zealand GeoNet Project


3 December-9 December 2008

The Alert Level for Tongariro was lowered to 0 (typical background activity) on 2 December. The number of volcanic earthquakes declined to background levels since mid-2008. In addition, regular measurements of volcanic gas levels and the temperature of the summit gas vent showed no changes over the previous two and a half years.

Source: New Zealand GeoNet Project


1 November-7 November 2006

Seismic activity from Tongariro continued to remain elevated during 27 July-1 November. Temperature and gas-concentration measurements from the summit remained normal. The Volcanic Alert Level remained at Level 1 (some signs of unrest).

Source: New Zealand GeoNet Project


14 June-20 June 2006

According to GeoNet on 14 June, seismic activity at Ngauruhoe (the youngest cone of the Tongariro complex) remained elevated. The Alert Level remained at 1.

Source: New Zealand GeoNet Project


7 June-13 June 2006

According to GeoNet, the number of small low-frequency earthquakes at Ngauruhoe (the youngest cone of the Tongariro complex) increased in the past 3 weeks. On 6 June, the Alert Level was raised to 1.

Source: New Zealand GeoNet Project


Index of Bulletin Reports


Reports are organized chronologically and indexed below by Month/Year (Publication Volume:Number), and include a one-line summary. Click on the index link or scroll down to read the reports.

02/1974 (CSLP 74-19) Steam and ash eruption in late January

04/1974 (CSLP 74-19) Two vents active within the crater during overflight on 29 March

03/1975 (CSLP 75-19) Strong explosive ash eruptions during 12-19 February

07/1977 (Ref 1977) Eruption columns rise 900 m

05/1983 (SEAN 08:05) Earthquake swarms

05/1992 (BGVN 17:05) Fumarole temperatures and gas chemistry unchanged from 1989; no significant deformation or seismicity

07/1993 (BGVN 18:07) Fumarole temperatures decrease

05/1994 (BGVN 19:05) Fumarole temperatures continue to decline; no deformation

05/1995 (BGVN 20:05) No fumarolic activity in Ngauruhoe crater or deformation

12/2006 (BGVN 31:12) Elevated seismicity at Ngauruhoe during May-October 2006

01/2009 (BGVN 34:01) High seismicity in January 2008; declined to background by mid-year

07/2012 (BGVN 37:07) Seismicity preceded phreatic explosion; associated rainfall-fed lahar




Bulletin Reports

All information contained in these reports is preliminary and subject to change.


02/1974 (CSLP 74-19) Steam and ash eruption in late January

Card 1790 (05 February 1974) Steam and ash eruption in late January

"Ngauruhoe volcano went into eruption on 22 January 1974. In the evening it was erupting red-hot blocks to a height of several hundred feet and at times down the outer flanks. Aerial inspections on 23 and 24 January, while the eruption of steam and ash continued with varied but moderate intensity, showed no lava to be visible in the crater within at least 100 m of the rim. During this stage of the eruption, blue flames of burning sulphur were seen at a fumarole about 200 m down the N flank.

"Ash eruption continued, interspersed by occasional violent explosions which reached maximum intensity on 26 and 27 January, when a number of explosive eruptions momentarily enveloped the entire summit in ash and sent large blocks cascading down the sides. A number of hot avalanches were observed. By 28 January the frequency of the eruptions was decreasing.

"The activity is continuing but on a reduced scale. The volcano has been intermittently active on a minor scale over the past year but not very impressively. The present activity is more in the nature of a major eruption."

Information Contacts: J. Healy, New Zealand Geological Survey.

04/1974 (CSLP 74-19) Two vents active within the crater during overflight on 29 March

Card 1839 (10 April 1974) Two vents active within the crater during overflight on 29 March

A scientific party of four plus two pilots left Paraparaumu on the morning of 29 March 1974 by Aero Commander to survey the White Island/Tongariro Volcanoes. The following is the report on the Ngauruhoe observation:

"The aircraft made several passes over the eastern side of Ngauruhoe from 1000 to 1015. There was a vigorous light grey ash column rising to approximately 4,000 m, and drifting WNW. Fine ash was falling from the ash cloud and there was a thin covering of recently deposited ash over the whole of the western side of Tongariro. Red Crater had lost its characteristic color and was a uniform light grey. Banks of cumulus cloud had built up on the NW of the mountain probably due to the presence of ash within the cloud. Elsewhere there was no cloud. Haze existed over the area between Ngauruhoe and Lake Taupo, probably also due to dust particles from the eruption. There appeared to be two vents within Ngauruhoe crater. Ash was being erupted from a northerly vent and white steam from a southerly vent. It was not possible to look into the crater to estimate the depth of the lava column. The volcano was in a Vulcanian phase of eruption with widespread distribution of fine ash. No blocks were observed to be ejected during the duration of the observations."

Information Contacts: J.W. Cole, Victoria University of Wellington, New Zealand.

03/1975 (CSLP 75-19) Strong explosive ash eruptions during 12-19 February

Card 2119 (12 March 1975) Strong explosive ash eruptions during 12-19 February

Ngauruhoe volcano erupted ash intermittently between 12 and 19 February in the first major activity since March 1974. Bad weather restricted observations, but several explosive ash eruptions occurred. An aerial inspection on the morning of 19 February revealed no obvious change in crater topography, and no new large ejecta on the summit. No ash emission was occurring. At about 1300 on 19 February (NZ Daylight Time) Ngauruhoe suddenly commenced the most voluminous pyroclastic eruption since the 1954 lava flows. A coherent, strongly convoluting eruption column rose to 11,000 m above sea level (8,700 m above the summit), spreading out into an ash cloud reaching 14,600 m above sea level. Continual ash emission was accompanied by a series of visible air shock waves, loud explosions, and large pyroclastic avalanches down the slopes of the 600-m-high cone. Incandescent ejecta was clearly visible in the eruption column. Walking parties within 2 km of the crater were pelted with scoria, and one group was nearly over-run by hot avalanches which passed close to the walking tracks. This eruption was accompanied by vigorous volcanic tremor and lasted until about 1420 on 19 February, when ash emission ceased. Ash was blown 160 km to the NNW to fall on Hamilton City.

A series of violently explosive eruptions followed periods of quiescence later in the afternoon. Explosions were accompanied by large visible air shock waves, closely followed by ejection of very large blocks (many up to 20 m above the crater. Extremely loud and very sharp reports were heard close to the volcano, loud rumblings being heard at least 70 km distant. Very dense eruption slugs expanded violently above the crater to envelop the summit and collapse into large pyroclastic avalanches which flowed rapidly down the cone. Impacting blocks raised large dust clouds down the cone, and set fire to tussock grass on surrounding areas. Smaller blocks (up to 1 m across) were thrown 2 km to the N, forming 2-m-diameter craters near walking tracks on Mt. Tongariro. Sharp volcanic earthquakes accompanied each explosion, which were preceded by periods of low seismic activity. Incandescent ejecta was observed during the night of 19-20 February as activity waned.

Bad weather restricted observations on 20-21 February, but steam explosions and small mud flows were observed. A helicopter landing on the summit was made on 22 February. The summit was covered by large blocks of lava which had been plastic on impact, the largest measuring 27 m long. Part of the western crater wall had collapsed into the vent. The crater was no deeper than after March 1974, due to infilling by collapse of vent walls, and possibly upward movement of a lava plug. No liquid lava was apparent in the vent. Strong gas emission (including SO2) prevented clear observations and measurements within the crater, which appeared to be between 50 and 100 m deep. A further explosive eruption was reported on 23 February.

Information Contacts: B.W. Marshall, University of Auckland, New Zealand.

07/1977 (Ref 1977) Eruption columns rise 900 m

The NZGS reports that cigar-shaped eruption columns rose to 900 m above the crater on 4 July 1977 at 0800 and 1030.

Information Contacts: New Zealand Geological Survey.

05/1983 (SEAN 08:05) Earthquake swarms

The following seismic data, from Balsillie and Latter (1985), replaces the first two sentences of the original report, which dealt only with 16 May seismicity. [Three swarms of A-type earthquakes were recorded during the first half of 1983. The first and smallest included 14 events to M 1.8 on 16-19 February. About 20 A-type and 4 B-type (including the largest, at magnitude 2.4) shocks occurred 1-7 April, plus two episodes of possible volcanic tremor (for 7 hours on 2 April and 10 hours on 4 April). The largest swarm began gradually on 7 May, peaked 14-16 May (maximum magnitude 2.1), and ended about 29 May, accompanied by 4 more episodes of possible volcanic tremor. During the strongest activity, 15-20 events of M >1.0 were recorded daily.]

On 10 May, NZGS personnel measured temperatures of the hot gases issuing from the crater bottom. Rockfalls from the overhanging E crater wall and growing talus fans had reduced the degassing area. Temperatures of 320-350°C were measured 1-2 m from the accessible edge of the hot area. These reflected a nearly steady decrease: 620° (1 July 1978), 520° (24 February 1979), 478° (25 June 1981), 418° (21 January 1982), 458° (10 June 1982), [349° (4 May 1983) and 105° (7 February 1985]. Ngauruhoe last erupted 12-23 February 1975, when strong explosive activity sent eruption plumes to 10 km and pyroclastic flows moved down the flanks (Nairn and Self, 1978).

Reference. Nairn, I.A., and Self, S., 1978, Explosive eruptions and pyroclastic avalanches from Ngauruhoe in February 1975: JVGR, v. 3, p. 39-60.

Further Reference. Balsillie, F.H., and Latter, J.H., 1985, Volcano-seismic activity at Ngauruhoe during 1983: New Zealand Volcanological Record, no. 13, p. 66-71.

Information Contacts: W. Giggenbach, DSIR, Wellington.
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05/1992 (BGVN 17:05) Fumarole temperatures and gas chemistry unchanged from 1989; no significant deformation or seismicity

Fumarole temperatures (93.9 & 94.3°C) and preliminary gas chromatograph data collected on 7 April were unchanged since the previous fieldwork in March 1989. No significant deformation was evident. Seismicity has remained relatively low.

Information Contacts: P. Otway, DSIR Geology & Geophysics, Wairakei.
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07/1993 (BGVN 18:07) Fumarole temperatures decrease

The following ... is based on fieldwork in late March and early May 1993. "Activity in the crater of Ngauruhoe has declined further over the past year and is at an all time low since records were first kept. Fumarole temperatures have decreased to 90°C after remaining stable at 94°C (boiling point for altitude) since 1986. No volcanic deformation was identified by surveys to points on the crater rim and at the base of the mountain."

Information Contacts: B. Christenson, I. Nairn, P. Otway, and B. Scott, IGNS, Wairakei.
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05/1994 (BGVN 19:05) Fumarole temperatures continue to decline; no deformation

Annual fieldwork was carried out on 30 March and 29 April 1994. Maximum fumarole temperatures had fallen to 78°C by the end of April. ... There was insufficient fumarole discharge for adequate sampling, and temperatures and pressures were at the lowest levels ever recorded. Except for minor landslide debris, no significant changes were noted in the Ngauruhoe crater.

Tilt leveling surveys were carried out at the Tama Lakes (1.7 km SSW) and Mangatepopo (1.8 km NNW) locations on 30 March. Apparent tilt recorded at Tama Lakes during the previous 11 months represented 4 µrad of inflation, but was within the range of random fluctuations recorded since installation in 1978. At Mangatepopo approximately 14 µrad of tilt towards Ngauruhoe (deflation) was recorded over the same period. This is ~2-3x the past noise level resulting from normal survey errors and seasonal movements. The most likely explanation, based on earlier experiences, is that two benchmarks near a walking trail have settled.

Repairs were made to the three highest crater rim stations on 30 March and two new stations were installed; two old stations are scheduled for removal after the 1995 survey. All six rim sites were surveyed for horizontal deformation on 29 April. Measurements were made by EDM and theodolite from 2 km N on Tongariro volcano. Relative movement vectors for the 1992-94 period at three stations were well within the normal noise range. Instabilities noted at the other sites resulted from various surface movements. Overall, there was no indication of recent volcanic deformation.

Geological mapping of the crater, N flank, and SW flank accomplished during these visits is part of the ongoing mapping project of the Tongariro complex.

Information Contacts: P. Otway, IGNS Wairakei.
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05/1995 (BGVN 20:05) No fumarolic activity in Ngauruhoe crater or deformation

Extremely low activity levels were found during an annual crater inspection and deformation survey on 11 May in the crater and at the base of Ngauruhoe. Crater fumaroles failed to discharge gases: the first complete absence of activity ever previously reported there. However, the NE rim of the outer crater was steaming vigorously as in the past. Neither horizontal nor vertical deformation were of sufficient magnitude to suggest volcanic significance. The current level of crater activity is probably the lowest in recorded history.

Ngauruhoe is the highest and most recent of more than a dozen composite cones that comprise the large Tongariro volcanic massif N of Ruapehu. Ten years ago, in February 1975, Ngauruhoe produced its last eruption, an event that generated 10-km-high plumes and pyroclastic flows. In 1983 several seismic swarms were recorded.

Information Contacts: P.M. Otway, Institute of Geological and Nuclear Sciences (IGNS), Private Bag 2000, Wairakei, New Zealand.
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12/2006 (BGVN 31:12) Elevated seismicity at Ngauruhoe during May-October 2006

Ngauruhoe is the youngest and highest volcanic cone (figure 1) of the Tongariro volcanic complex on the North Island of New Zealand. According to New Zealand GeoNet Project volcanologists, the number of small (less than magnitude 2), low-frequency earthquakes near Ngauruhoe recorded by seismometers increased from less than five per day at the beginning of May 2006 to more than 20/day by the end of May. Typically, only a few earthquakes of any type are recorded in the vicinity of Ngauruhoe each year. In 1983, 1991, and 1994 there were clusters of similar earthquakes recorded near Ngauruhoe, but there have been very few recorded since then. Due to the increased seismicity, the Scientific Alert Level was raised to Alert Level 1 (some signs of unrest) on 6 June. Earthquakes of this type are commonly interpreted as being related to the movement of magma and/or volcanic gases.

Figure 1. Snow covered Mt. Ngauruhoe as seen on 28 July 2006. Photo credit to University of Auckland Snowsports Club.

Earthquakes peaked in early June at about 50/day and then declined to about 10-20/day by the 14th, with the largest about magnitude 1. Seismic activity has remained elevated through the middle of December 2006. Initial observations suggested that hypocenters were 1-4 km deep, slightly N or E of the summit. By mid-June volcanologists had installed three additional seismographs around the base of Ngauruhoe, including one that could be monitored in real-time. Between 14 June and 3 July the number of volcanic earthquakes recorded near Ngauruhoe has varied between approximately 20 and 40 per day. Using data from the additional seismographs, volcanologists were able to refine the location of the earthquakes to within about 1 km of the surface beneath the N flank; the largest events were approximately magnitude 1. Elevated seismicity continued at up to 30 events/day through October 2006.

As of the last GeoNet report on 1 November, no other signs of unrest had been recorded. Multiple measurements showed that temperatures and volcanic gas concentrations have not changed since the increased seismicity began in May, and were similar to measurements made in 2003. Carbon-dioxide release through the soil (from degassing magma) is also similar to measurements in 2003. The maximum fumarole temperature near the summit is about 85°C. Reports of steaming in the summit area were investigated, but because no new features were seen that could have caused emissions, the sightings were attributed to clouds rather than volcanic activity.

Information Contacts: New Zealand GeoNet Project, a project sponsored by the New Zealand Government through these agencies: Earthquake Commission (E.C.), Geological and Nuclear Sciences (GNS), and Foundation for Research, Science and Technology (FAST) (URL: http://www.geonet.org.nz/) (URL: http://data.geonet.org.nz/geonews/sab); University of Auckland Snowsports Club, University of Auckland, New Zealand (URL: http://www.uasc.co.nz/).
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01/2009 (BGVN 34:01) High seismicity in January 2008; declined to background by mid-year

Our most recent report on Tongariro (BGVN31:12) discussed elevated seismicity during May-October 2006. The M < 2 long-period seismic event occurred near Ngauruhoe, the youngest cone of the Tongariro volcanic complex.

Between 1 November 2006 and January 2008, elevated, low-level volcanic earthquakes continued at Ngauruhoe. The number of events per day typically ranged between 5 and 30. Then, on 6 January 2008, the number of events per day began to increase, and by 9-10 January the number had shot up to 80 per day, before decreasing slightly. The larger events ranged between M 1.2 and 1.5.

In response to these changes, volcanologists from GeoNet visited on 17 January 2008 and measured gas concentrations, temperatures, and soil gas flux at the summit area of Ngauruhoe. The resulting data were similar to measurements made in 2006-2007. The maximum fumarole temperature near the summit remained about 86°C. No other signs of unrest were found. The data suggested that the earthquakes were occurring within about 1 km of the surface beneath the N flank.

GeoNet noted that the number of volcanic earthquakes since mid-2008 has declined to background levels. Regular measurements of volcanic gas levels and the temperature of the summit gas vent have showed no changes over the previous two and a half years. Consequently, on 2 December 2008, the Alert Level was lowered from 1 to 0 (typical background activity). No thermal anomalies have been measured by MODIS/MODVOLC satellites (HIGP Hot Spots System) in the at least the past 5 years.

Information Contacts: New Zealand GeoNet Project, a collaboration between the Earthquake Commission and GNS Science, Wairakei Research Centre, Private Bag 2000, Taupo 3352, New Zealand (URL: http://www.geonet.org.nz/); Hawai'i Institute of Geophysics and Planetology (HIGP) Hot Spots System, University of Hawai'i, 2525 Correa Road, Honolulu, HI 96822, USA (URL: http://hotspot.higp.hawaii.edu/).
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07/2012 (BGVN 37:07) Seismicity preceded phreatic explosion; associated rainfall-fed lahar

Elevated seismicity in July 2012 preceded a phreatic eruption at Tongariro on 6 August. The eruption ejected blocks of old lava from the crater area, and triggered a debris flow down a drainage on a flank of the volcano. Six days later, heavy rainfall remobilized some of the debris flow and generated a small flood/lahar that crossed a state highway. This report summarizes GeoNet alert bulletins and Taupo Civil Defense postings concerning the phreatic explosion and associated events (through 17 August 2012).

Precursory seismicity. GeoNet reported elevated numbers of volcanic earthquakes (M < 2.5) beginning on 13 July (figure 2). Seismicity then declined until 18 July, when volcanic earthquakes returned, increasing in magnitude and abundance through 20 July. The earthquakes were clustered between Emerald Lake and the SE shore of Lake Rotoaira at 2-7 km depth; a subset of the earthquakes were tightly clustered between Blue Lake and Te Maari (Te Mari) Craters within the same depth range (figures 2 and 3). As a result, the Volcano Alert Level was raised from 0 to 1 (on a scale from 0-5) and the Avation Colour Code was raised from Green to Yellow (on a four color scale; Green-Yellow-Orange-Red) on 20 July.

Figure 2. Seismicity at Tongariro during 11 July-6 August 2012, leading up to a phreatic eruption at 2350 on 6 August. Shown are the number of seismic events per day (107 in total, top panel), the depth at which each event occurred (and associated error bars, middle panel), and the magnitude of each event (bottom panel). Courtesy of GeoNet.
Figure 3. Mapped epicenters of seismic events recorded at Tongariro during 25 May-23 August 2012. A phreatic eruption occurred late on 6 August (see figure 2). During the precursory activity (late July and early August), seismicity concentrated between Emerald Lake (E) and Lake Rotoaira (R), with a cluster between Blue Lake (B) and Te Maari Craters (T). Courtesy of GeoNet.

By 23 July, GeoNet had deployed four portable seismometers and had sampled springs and fumaroles. They reported that provisional analyses of gas samples indicated a marked increase in volcanic gases above typical mixtures of hydrothermal and volcanic gas signatures (see subsection “Ash and gas analyses” for detail). By 31 July, GeoNet had also installed a GPS instrument to monitor any deformation.

Phreatic eruption. At 2352 on 6 August, a phreatic eruption occurred from a vent located within the Te Maari Craters area. An explosion generated seismic signals that lasted a few minutes, followed by a series of discrete small earthquakes during the next few tens of minutes. Within 35 minutes, GeoNet posted an Alert Bulletin announcing that ashfall had been reported; the Volcano Alert Level was raised to 2 and the Aviation Colour Code was raised to Red. Taupo Civil Defense responded by closing State Highways 1 and 46 (to the E and N of Tongariro, respectively).

Approximately one hour after the eruption, the Cooperative Institute for Meteorological Satellite Studies (CIMSS) observed in satellite imagery that an ash plume was drifting more than 50 km E from Tongariro (figure 4). They also reported that airports had cancelled flights at Gisborne (210 km ENE), Rotorua (120 km NNE), Taupo (60 km NE), and Palmerston North (135 km S).

Figure 4. A Visible Infrared Imaging Radiometer Suite (VIIRS) image acquired by the Suomi National Polar-orbiting Partnership (NPP) satellite at 1252 UTC on 6 August 2012 (0052 NZST on 7 August) showing an ash plume drifting more than 50 km E from Tongariro, after the phreatic explosion ~1 hour earlier. The windward end of the plume remains over the volcano, implying ongoing emissions. In the main image, the North Island of New Zealand is outlined in teal, and Rotorua is labeled to the N of the plume. In both images, the ash plume is labeled in yellow, and Tongariro is labeled in red, just W of the plume. Courtesy of CIMSS.

GeoNet reported that no volcanic tremor occurred before or after the event, and the Aviation Colour Code was reduced to Orange ~12 hours later (about 1200 on 7 August), and reduced again the next day (1500 on 8 August).

GeoNet conducted an observation flight on 8 August and photographed a variety of features discussed and illustrated in more detail below. They included: (1) a new vent area residing in a small crater, and associated steaming fissures, (2) a debris flow, and (3) impact craters.

The new vent(s) are located in the Upper Te Maari Craters area (figure 5a); low clouds prevented scientists from viewing areas higher than the lowest parts of Upper Te Maari Crater. Photographs of the area revealed a nearby steaming eruptive fissure, and more intense steaming in areas of ground that had been steaming prior to the eruption (figure 5b).

Figure 5. Photographs taken after Tongariro’s 6 August 2012 phreatic eruption showing the Upper Te Maari vent area. In (A) the view is looking SE towards Upper Te Maari crater, with areas of fumaroles and a new vent on the outer edge of the crater (indicated by the arrow). (B) is looking NW showing vents along a fissure around the S side of Upper Te Maari crater. Upper Te Maari crater is indicated in each photo with the '*' symbol. Both photographs were taken during a morning observation flight on 8 August 2012. Courtesy of GeoNet.

A debris flow generated by the phreatic eruption comprised rock and soil debris that blocked a stream valley draining NW from the Te Maari Craters area (figure 6). GeoNet reported water ponding around the edges, and ash that had been remobilized into slurry flows. GeoNet noted that areas of the debris flow (especially in the upper sections) had eroded into the substrate (figure 6a).

Figure 6. Upper (A) and lower (B) portions of the debris flow generated by the 6 August 2012 phreatic eruption at Tongariro. The debris flow extended down a stream valley draining NW from the Te Maari Craters (steaming areas visible in the top-most portion of (A)). White asterisks in both photos indicate regions where the debris flow eroded into the substrate. White arrows in (B) indicate areas of newly ponded water at the edges of the flow. Courtesy of GeoNet.

The explosion ejected blocks of lava up to 2 km from the Te Maari Craters area, leaving impact craters in vegetation and ground surfaces (figure 7). All blocks were angular, and none were steaming or surrounded by burnt vegetation; GeoNet thus concluded that the blocks comprised old (non-juvenile) lava(s) ejected from the vent area.

Figure 7. Blocks of lava ejected up to 2 km from the Te Maari Craters area during the phreatic explosion on 6 August 2012 left impact craters in vegetation and ground surfaces (circled). Courtesy of GeoNet.

Ash and gas analyses. Textural analyses indicated that the ash emitted during the 6 August explosion contained little-to-no fresh (juvenile) lava, suggesting that the eruption was primarily steam driven (phreatic). GeoNet also reported that analysis of the fluorine content of the ash indicated that, except in the immediate vicinity of the volcano, there were little health or agricultural concerns.

For 9 August, GeoNet reported emissions of 2,100 tons/day of SO2, 3,900 tons/day of CO2, and 364 tons/day of H2S from vents. Sulfur (H2S) smells were reported in downwind locations during 11-12 August, and further reports were filed from the Manawatu region on 15 August. GeoNet attributed the sulfur odors to “passive degassing of magma beneath the surface of Tongariro.”

Heavy rains spawn minor lahar. In concert with the 11 August release of a new, updated hazard map of Tongariro (figure 8), GeoNet warned motorists not to stop their vehicles along Highway 46 (N of Tongariro) due to hazards in that area. Following heavy rains the next morning, a minor flood/lahar crossed State Highway 46 near the S tip of Lake Rotoaira (at a location ~6 km W of Rangipo). According to the New Zealand Herald, a driver described 13-cm-deep mud crossing the road at 0830 that day. Scientists at GNS Science stressed that the lahar was not a direct result of an eruptive process, and a resident reported that the area was commonly washed out during heavy rains.

Figure 8. The updated hazard map released by GeoNet on 11 August 2012, which includes the 6 August vents seen in Tongariro’s Te Maari Craters area (dashed black circle). As seen in the legend, the map indicates the locations prone to pyroclastic flows and mudflows (shaded yellow) and an area within a 3 km radius of the summit that is prone to gas hazards and flying rocks (shaded orange). Where the two zones overlap, the map is shaded red. Red dots indicate eruptive vents active in the last 27,000 years. Orange triangular “hut” icons indicate nearby mountain refuges. The larger poster conveys extensive hazard information. Note disclaimer (upper left) and wide range of agency collaboration (lower right) in map production. The highest peak of the complex is at Ngauruhoe (near the SW corner of the map). As stated in the comment in the SW corner of the map, “Tongariro and Ngauruhoe are parts of one active volcanic system.” Courtesy of GeoNet.

Ten days after the phreatic explosion, GeoNet reduced the Volcano Alert Level to 1, stating that minor eruptive activity, required for Volcanic Alert Level 2, had ceased. The Aviation Colour Code remained at Yellow as of 24 August 2012.

Information Contacts: GeoNet, a collaboration between the Earthquake Commission and GNS Science (URL: http://www.geonet.org.nz/); GNS Science, Wairakei Research Center, Private Bag 2000, Taupo 3352, New Zealand (URL: http://www.gns.cri.nz/); Earthquake Commission (EQC), PO Box 790, Wellington, New Zealand (URL: http://www.eqc.govt.nz/); The Cooperative Institute for Meteorological Satellite Studes (CIMSS), a collaboration between the University of Wisonsin-Madison, the National Oceanic and Atmospheric Administration, and the National Aeronautics and Space Administration, Space Science and Engineering Center, 1225 W. Dayton St., Madison, WI 53706 (URL: http://cimss.ssec.wisc.edu/); University of Wisconsin-Madison (UW-Madison) (URL: http://www.wisc.edu/); National Oceanic and Atmospheric Administration (NOAA) (URL: http://www.noaa.gov/about-noaa.html); National Aeronautics and Space Administration (NASA) (URL: http://www.nasa.gov/); New Zealand Herald (URL: http://www.nzherald.co.nz/).
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Tongariro is a large andesitic volcanic massif, located immediately NE of Ruapehu volcano, that is composed of more than a dozen composite cones constructed over a period of 275,000 years. Vents along a NE-trending zone extending from Saddle Cone (below Ruapehu volcano) to Te Mari crater (including vents at the present-day location of Ngauruhoe) were active during several hundred years around 10,000 years ago, producing the largest known eruptions at the Tongariro complex during the Holocene. North Crater stratovolcano, one of the largest features of the massif, is truncated by a broad, shallow crater filled by a solidified lava lake that is cut on the NW side by a small explosion crater. The youngest cone of the complex, Ngauruhoe, has grown to become the highest peak of the massif since its birth about 2500 years ago. The symmetrical, steep-sided Ngauruhoe, along with its neighbor Ruapehu to the south, have been New Zealand's most active volcanoes during historical time.

Summary of Holocene eruption dates and Volcanic Explosivity Indices (VEI).

Start Date Stop Date Eruption Certainty VEI Evidence Activity Area or Unit
2012 Nov 21 2012 Nov 21 Confirmed 2 Historical Observations Upper Te Maari Craters
2012 Aug 6 2012 Aug 7 Confirmed 2 Historical Observations Upper Te Maari Craters
1977 Jul 4 1977 Jul 4 Confirmed 1 Historical Observations Ngauruhoe
1976 Aug 23 1976 Aug 28 Confirmed 1 Historical Observations Ngauruhoe
1975 Feb 12 1975 Feb 23 Confirmed 3 Historical Observations Ngauruhoe
1972 Nov 22 1974 Aug 19 Confirmed 3 Historical Observations Ngauruhoe
1972 Mar 19 1972 Jun 6 Confirmed 2 Historical Observations Ngauruhoe
1969 Jan 21 Unknown Confirmed 2 Historical Observations Ngauruhoe
1968 Aug 18 Unknown Confirmed 2 Historical Observations Ngauruhoe
1962 May 24 Unknown Confirmed 2 Historical Observations Ngauruhoe
1959 Jun 1 Unknown Confirmed 2 Historical Observations Ngauruhoe
1958 Nov 5 1958 Nov 18 (?) Confirmed 2 Historical Observations Ngauruhoe
1956 Jan 11 1956 Feb 11 Confirmed 2 Historical Observations Ngauruhoe (south sub-crater)
1954 May 13 1955 Jun 25 Confirmed 3 Historical Observations Ngauruhoe (south sub-crater)
1953 Dec 28 (in or before) Unknown Confirmed 0 Historical Observations Ngauruhoe (south sub-crater)
1952 Nov 29 1953 Jul Confirmed 2 Historical Observations Ngauruhoe (south sub-crater)
1951 May Unknown Confirmed 2 Historical Observations Ngauruhoe
1950 Jun 16 Unknown Confirmed 2 Historical Observations Ngauruhoe
1949 Feb 9 1949 Mar 3 Confirmed 2 Historical Observations Ngauruhoe (south sub-crater)
1948 Sep Unknown Confirmed 2 Historical Observations Ngauruhoe
1948 Apr 30 1948 May Confirmed 2 Historical Observations Ngauruhoe
1940 Sep 1940 Oct Confirmed 2 Historical Observations Ngauruhoe
1939 Aug Unknown Confirmed 2 Historical Observations Ngauruhoe
1937 Jan Unknown Confirmed 2 Historical Observations Ngauruhoe
1934 Dec 1935 Feb Confirmed 2 Historical Observations Ngauruhoe
1934 Jun Unknown Confirmed 2 Historical Observations Ngauruhoe
1931 Feb 1931 May Confirmed 2 Historical Observations Ngauruhoe
1928 Jul Unknown Confirmed 2 Historical Observations Ngauruhoe
1928 Mar 3 Unknown Confirmed 2 Historical Observations Ngauruhoe
[ 1927 ] [ Unknown ] Uncertain 1   North flank (Ketetahi)
1926 Dec 21 1926 Dec 30 (?) Confirmed 2 Historical Observations Ngauruhoe
1926 Apr 16 1926 Jun Confirmed 2 Historical Observations Ngauruhoe and Red Crater
1925 Nov 1925 Dec Confirmed 2 Historical Observations Ngauruhoe
1924 Oct 1924 Nov Confirmed 2 Historical Observations Ngauruhoe
1924 May 22 Unknown Confirmed 2 Historical Observations Ngauruhoe
1924 Jan 9 1924 Jan 30 Confirmed 2 Historical Observations Ngauruhoe
1917 Oct 1917 Nov Confirmed 2 Historical Observations Ngauruhoe
1914 Sep 1914 Oct Confirmed 2 Historical Observations Ngauruhoe
1913 May Unknown Confirmed 2 Historical Observations Ngauruhoe
1913 Jan Unknown Confirmed 2 Historical Observations Ngauruhoe
1910 Oct 1911 Jan Confirmed 2 Historical Observations Ngauruhoe
1910 Jan Unknown Confirmed 2 Historical Observations Ngauruhoe
1909 Mar 1909 Jul Confirmed 2 Historical Observations Ngauruhoe
1907 Nov Unknown Confirmed 2 Historical Observations Ngauruhoe
1907 Feb 1907 May Confirmed 2 Historical Observations Ngauruhoe (south sub-crater)
1906 Mar Unknown Confirmed 2 Historical Observations Ngauruhoe
1905 Unknown Confirmed 2 Historical Observations Ngauruhoe
1904 Nov 22 Unknown Confirmed 2 Historical Observations Ngauruhoe
1898 Jan Unknown Confirmed 2 Historical Observations Ngauruhoe
1897 Unknown Confirmed 2 Historical Observations Ngauruhoe
1896 Nov 1896 Dec 26 ± 5 days Confirmed 2 Historical Observations NE flank (upper Te Mari Crater)
1892 Nov 30 Unknown Confirmed 2 Historical Observations NE flank (upper Te Mari Crater)
1892 Nov 1892 Dec Confirmed 2 Historical Observations Ngauruhoe
1892 Feb 1892 Mar Confirmed 2 Historical Observations Ngauruhoe
[ 1890 Mar ] [ Unknown ] Uncertain 1   SSE flank (Red Crater)
1886 Jun Unknown Confirmed 2 Historical Observations NE flank (upper Te Mari Crater)
1885 ± 1 years 1887 Confirmed 1 Historical Observations SSE flank (Red Crater)
1883 Apr 25 ± 5 days Unknown Confirmed 2 Historical Observations Ngauruhoe (south sub-crater)
1881 Jul 6 Unknown Confirmed 2 Historical Observations Ngauruhoe
1878 Sep 1 ± 120 days Unknown Confirmed 2 Historical Observations Ngauruhoe (NW sub-crater)
[ 1875 Oct 1 ± 90 days ] [ Unknown ] Uncertain 2   Ngauruhoe
1870 Apr 1870 Aug Confirmed 2 Historical Observations Ngauruhoe (NW sub-crater)
1869 Aug Unknown Confirmed 2 Historical Observations Ngauruhoe
1869 Unknown Confirmed 2 Historical Observations NE flank (Upper Te Mari Crater)
1864 Dec 1865 Jan Confirmed 2 Historical Observations Ngauruhoe
1863 1864 Apr Confirmed 2 Historical Observations Ngauruhoe
1862 Jan Unknown Confirmed 2 Historical Observations Ngauruhoe
1859 Apr 21 Unknown Confirmed 1 Historical Observations SSE flank (Red Crater)
1857 Feb 1857 Mar Confirmed 2 Historical Observations Ngauruhoe
1855 Unknown Confirmed 2 Historical Observations SSE flank (Red Crater)
1844 Oct 1845 Jan Confirmed 2 Historical Observations Ngauruhoe
1841 Unknown Confirmed 2 Historical Observations Ngauruhoe
1839 Feb 1839 Mar Confirmed 1 Historical Observations Ngauruhoe
1500 ± 50 years Unknown Confirmed   Tephrochronology Upper Te Mari Craters
0550 BCE ± 200 years Unknown Confirmed 5 Radiocarbon (uncorrected) Ngauruhoe and Red Crater
9350 BCE (?) Unknown Confirmed 5 Tephrochronology Tama Lakes to Te Mari
9450 BCE (?) Unknown Confirmed 5 Radiocarbon (corrected) Saddle cone area to Half Cone
9650 BCE (?) Unknown Confirmed 5 Tephrochronology Saddle Cone to Half Cone
9850 BCE (?) Unknown Confirmed   Radiocarbon (corrected) UT1 tephra

This compilation of synonyms and subsidiary features may not be comprehensive. Features are organized into four major categories: Cones, Craters, Domes, and Thermal Features. Synonyms of features appear indented below the primary name. In some cases additional feature type, elevation, or location details are provided.


Cones

Feature Name Feature Type Elevation Latitude Longitude
Ngauruhoe
    Auruhoe
Stratovolcano 2291 m 39° 9' 24" S 175° 37' 57" E
Pukekaikione Cone 1680 m 39° 9' 0" S 175° 34' 0" E
Pukeonake Cone 1225 m 39° 9' 0" S 175° 36' 0" E

Craters

Feature Name Feature Type Elevation Latitude Longitude
Blue Lake Crater 1686 m 39° 8' 0" S 175° 40' 0" E
North Crater Crater 1830 m 39° 7' 0" S 175° 41' 0" E
Red Crater Crater 1860 m 39° 8' 0" S 175° 41' 0" E
Te Mari
    Te Maari
    Puia Hou
    Sulphur Lagoon
Crater 1500 m 39° 7' 0" S 175° 40' 0" E

Thermal

Feature Name Feature Type Elevation Latitude Longitude
Ketetahi Thermal 1400 m 39° 6' 0" S 175° 41' 0" E
This telephoto view looking SW across Lake Taupo, the southernmost major caldera of the Taupo volcanic zone, shows several major peaks anchoring the southern end of the Taupo volcanic zone. The broad forested peak below the center horizon is the Pleistocene Pihanga volcano. The steep-sided cone on the horizon to its right is Nguaruhoe, the youngest volcano of the Tongarior complex. The broad massif to its right is Tongariro. The snow-capped massif on the left-center horizon is Ruapehu.

Photo by Tom Simkin, 1986 (Smithsonian Institution).
Pyroclastic flows sweep down the flanks of Ngauruhoe volcano on February 19, 1975, as a powerful, ash-laden eruption column rises above the summit crater. This eruption was one of the largest of Ngauruhoe in historical time. The eruption column rose 12 km above the vent, ash fell 160 km away on Hamilton City, and pyroclastic flows reached the base of the cone. Explosive activity had begun on the 12th and continued until the 23rd.

Photo by Graham Hancocks, 1975 (New Zealand Geological Survey).
A vulcanian explosion from Ngauruhoe volcano in New Zealand on February 19, 1975, ejects a dark, ash-laden cloud. Large, meter-scale ejected blocks trailing streamers of ash can be seen in the eruption column. Blocks up to 20 m across were projected hundreds of meters above the vent.

Photo by Ian Nairn, 1975 (New Zealand Geological Survey).
An aerial view from the south in the late 1970s shows a close-up of an explosion crater that cuts a flat-lying former lava lake on the summit of the North Crater cone of the Tongariro volcanic complex. The explosion pit which makes up the bulk of the slide is 400 m diameter.

Photo by Ian Nairn, late 1970s (New Zealand Geological Survey).
Two large andesitic volcanic massifs anchor the southern end of the Taupo volcanic zone. Tongariro, in the foreground, is a cluster of about a dozen composite cones dominated by the symmetrical Ngauruhoe stratovolcano. Ruapehu, in the background to the south, contains a frequently active crater lake. The two volcanoes have been the most active in New Zealand during historical time.

Photo by New Zealand Geological Survey, 1981.
The SE wall of Red Crater is cut by a vertical volcanic dike that fed eruptions along a NE-SW-trending fissure. Magma at the outer part of the dike cooled against the red scoria walls of Red Crater, while magma at the center of the dike partially drained away, leaving this cavity. Ngauruhoe stratovolcano towers in the background; it and Red Crater are two of the more than a dozen composite cones forming the Tongariro volcanic complex.

Photo by Jim Cole (University of Canterbury).
The black lava flows extending from the summit of Ngauruhoe volcano to its flanks were erupted in 1954. An eruption that began with explosive activity on May 13, 1954, was followed on June 4 by the emission of lava flows that traveled down the NW flank until September 26. Explosive activity, which constructed a cinder cone in the summit crater, continued until March 1955, and incandescent lava was present in the crater until June.

Photo by Jim Cole (University of Canterbury).
An ash plume on March 29, 1974, is deflected by the wind from the summit of Ngauruhoe volcano one day after powerful explosions that were accompanied by pyroclastic flows. Intermittent explosive eruptions had been occurring since November 22, 1972, and continued until August 19, 1974. Eruptions in January and March 1974 were the largest in two decades from Ngauruhoe.

Photo by Jim Cole, 1974 (University of Canterbury).
A roadcut along the desert road between Waiouru and Turangi exposes some of the tephra layers erupted from the Tongariro volcanic complex during its early stage of development. Conical Ngauruhoe volcano, which formed during the past 2500 years, rises in the background.

Photo by Jim Cole (University of Canterbury).
Lower Tama Lake, on the NE flank of Ruapehu volcano (upper left), was formed late in a series of eruptions that began about 10,000 years ago from vents ranging from the summit craters of Ruapehu to Te Mari craters of the Tongariro volcanic center. The Tama Lake eruptions included the emplacement of two lava flows from upper Tama Lake with a combined volume of 0.2 cu km and a smaller lava flow from lower Tama Lake.

Photo by Jim Cole (University of Canterbury).
An ash-rich eruption column ascends above Ngauruhoe volcano on January 26, 1974 in this view from the west. Small pyroclastic flows descend the upper flanks of the cone. Eruptions January 26-28 and March 27-29, 1974, were the most powerful at Ngauruhoe in two decades. Explosive activity had been occurring since November 1972, and lasted until August 1974. The dark streaks descending to the base of the cone at the left are lava flows from the 1954 eruption.

Photo by D.L. Homer, 1974 (New Zealand Geological Survey).
Snow-capped Ngauruhoe is a small 2291-m-high stratovolcano that was constructed during the past 2500 years. The symmetrical volcano, seen here from the NE, rises 800 m above its surroundings and is the highest peak of the Tongariro volcanic center. Tongariro is a large andesitic volcanic massif, located immediately NE of Ruapehu volcano, that is comprised of more than a dozen composite cones. Frequent explosive eruptions have been recorded from Ngauruhoe since its first historical activity in 1839.

Photo by Don Swanson, 1984 (U.S. Geological Survey).
Snow-capped Ngauruhoe volcano rises above the Mangatepopo track on the NW side of the volcano. The dark lobe in the right foreground is a deposit produced by lithic-rich pyroclastic flows during the 1975 eruption. Meter-scale ballastic clasts from powerful vulcanian explosions during the 1975 eruption were ejected to distances of 2.8 km, beyond the location of this photo.

Photo by Don Swanson, 1984 (U.S. Geological Survey).

The following references have all been used during the compilation of data for this volcano, it is not a comprehensive bibliography. Discussion of another volcano or eruption (sometimes far from the one that is the subject of the manuscript) may produce a citation that is not at all apparent from the title.

Cole J W, Graham I J, Hackett W R, Houghton B F, 1986. Volcanology and petrology of the Quaternary composite volcanoes of the Tongariro volcanic centre, Taupo volcanic zone. Roy Soc New Zeal Bull, 23: 224-250.

Cole J W, Hochstein M P, Skinner D N B, Briggs R M, 1986. Tectonic setting of North Island Cenozoic volcanism (Tour Guide C1). New Zeal Geol Surv Rec, 11: 5-60.

Graham I J, Hackett W R, 1987. Petrology of calc-alkaline lavas from Ruapehu volcano and related vents, Taupo Volcanic Zone, New Zealand. J Petr, 28: 531-567.

Green J, Short N M, 1971. Volcanic Landforms and Surface Features: a Photographic Atlas and Glossary. New York: Springer-Verlag, 519 p.

Hackett W R, Houghton B F, 1986. Active composite volcanoes of Taupo volcanic zone (Tour Guide C4). New Zeal Geol Surv Rec, 11: 61-114.

Hobden B J, Houghton B F, Lanphere M A, Nairn I A, 1996. Growth of the Tongariro volcanic complex: new evidence from K-Ar age determinations. New Zeal J Geol Geophys, 39: 151-154.

Hobden B J, Houghton B F, Nairn I A, 2002. Growth of a young, frequently active composite cone: Ngauruhoe volcano, New Zealand. Bull Volc, 64: 392-409.

IAVCEI, 1973-80. Post-Miocene Volcanoes of the World. IAVCEI Data Sheets, Rome: Internatl Assoc Volc Chemistry Earth's Interior..

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Shane P, Doyle L R, Nairn I A, 2008. Hetergeneous andesite-dacite ejecta in 26-16.6 ka pyroclastic deposits of Tongariro volcano, New Zealand: the product of multiple magma-mixing events. Bull Volc, 70: 517-536.

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Volcano Types

Stratovolcano(es)
Pyroclastic cone(s)

Tectonic Setting

Subduction zone
Continental crust (> 25 km)

Rock Types

Major
Andesite / Basaltic Andesite
Minor
Basalt / Picro-Basalt

Population

Within 5 km
Within 10 km
Within 30 km
Within 100 km
27
286
7,591
81,567

Affiliated Databases

Large Eruptions of Tongariro Information about large Quaternary eruptions (VEI >= 4) is cataloged in the Large Magnitude Explosive Volcanic Eruptions (LaMEVE) database of the Volcano Global Risk Identification and Analysis Project (VOGRIPA).
WOVOdat WOVOdat is a database of volcanic unrest; instrumentally and visually recorded changes in seismicity, ground deformation, gas emission, and other parameters from their normal baselines. It is sponsored by the World Organization of Volcano Observatories (WOVO) and presently hosted at the Earth Observatory of Singapore.
EarthChem EarthChem develops and maintains databases, software, and services that support the preservation, discovery, access and analysis of geochemical data, and facilitate their integration with the broad array of other available earth science parameters. EarthChem is operated by a joint team of disciplinary scientists, data scientists, data managers and information technology developers who are part of the NSF-funded data facility Integrated Earth Data Applications (IEDA). IEDA is a collaborative effort of EarthChem and the Marine Geoscience Data System (MGDS).
Smithsonian Collections Search the Smithsonian's NMNH Department of Mineral Sciences collections database. Go to the "Search Rocks and Ores" tab and use the Volcano Name drop-down to find samples.