Ngauruhoe Volcano - John Seach


North Island, New Zealand

39.16 S, 175.632 E
summit elevation 2291 m

Ngauruhoe is a stratovolcano located between Tongariro and Ruapehu volcanoes. Tongariro volcano is located 17 km NNE of Ruapehu, and about 260 km SSE of Auckland.

Ngauruhoe is a young cone with a 30 degree slope. The active vent is about 150 m wide crater of a scoria which formed on Ngauruhoe summit between 1954 and 1975. The cone is located within a 400 m wide, older crater. Ngauruhoe covers an area of 15 sq km and has a volume of 2.2 cubic km. The cone is well preserved and hasn't undergone significant mass wasting.

Ngauruhoe volcano - John Seach (2011)

Ngauruhoe volcano
Ngauruhoe volcano - John Seach

ngauruhoe volcano
Ngauruhoe volcano from Tongariro alpine crossing

Ngauruhoe volcano - John Seach

Eruptions at Ngauruhoe have rarely been more than nine years apart.
The volcano has been quiet since 1975 – the longest break in activity in its recorded history. Eruptions at Ngauruhoe are noted for their diversity. No single eruption type dominates. A single eruption can exhibit several eruption styles. This is similar to Lopevi volcano in Vanuatu.

2006 Earthquakes
Ngauruhoe was raised to level 1 alert in June 2006 due to an increase in earthquakes under the volcano. Earthquakes peaked in early June at about 50/day. The location of the earthquakes were about 1 km beneath the N flank. Temperature and gas emission from the summit remained unchanged. The maximum fumarole temperature near the summit was about 85°C.

1975 Eruptions
On 19th February 1975 an eruption produced pyroclastic flows and a 10km high ash plume. Blocks were ejected 2.8 km from the vent at velocities up to 400 m/s.

1974 Eruption
Explosive activity occurred at Ngauruhoe volcano between 27-30 March 1974. The activity lasted for a few hours and produced a cloud which reached altitude of 6000 m. Some incandescent blocks fell close to the cone. A study of eruptions from 1972-74 showed that a significant number were grouped around the fortnightly earth tidal maximum.

1973 Eruption
A new period of magmatic eruptions began at Ngauruhoe volcano on 2nd January 1973. Further small eruptions occurred in September and October.

1954-55 Eruptions
Strombolian eruptions occurred at Ngauruhoe volcano on 4th June 1954 after ash and block emissions for the previous few weeks. Over a period of 4 months at least 10 aa lava flows occurred. Eruptions ceased during September 1954 then resumed between December 1954 and March 1955. Atmospheric shock waves were observed in 1954.

1949 Eruption
An eruption of Ngauruhoe volcano began on 9th February 1949 after an hour of tremor. At the beginning of the eruption the crater filled with lava and overflowed the northwest side of the cone. Pyroclastic avalanches moved over a mile down NW side of the cone.

1948 Eruption
Large explosive activity occurred at Ngauruhoe volcano in April–May 1948. Ash rose 3000 m above the summit and explosions were heard 8 km away. Hot blocks up to 6 m in diameter were ejected on the north-west side of the cone, and rocks ‘the size of a small house’ were thrown out from the crater.

1870 Eruption
Two lava flows occurred at Ngauruhoe volcano on 7th July 1870. Explosive eruptions of incandescent scoria and short-lived ash plumes occurred. Loud explosions were heard 190 km away.

Ngauruhoe Volcano Eruptions

1975-77, 1972, 1968-69, 1962, 1958-59, 1956, 1948-54, 1939-40, 1937, 1934, 1931, 1924-28, 1917, 1913-14, 1909-10, 1904-07, 1897-98, 1892, 1883, 1881, 1878, 1875, 1869-70, 1862-64, 1857, 1844, 1841, 1839, 550 BC ± 200