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Taupō Rift | |
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Etymology | Lake Taupō |
Coordinates | 38°23′0″S176°14′0″E / 38.38333°S 176.23333°E (extends 37°30′S to 39°30′S) [1] |
Country | New Zealand |
Region | North Island |
Characteristics | |
Part of | Hikurangi Margin |
Segments | multiple |
Length | 300 km (190 mi) [2] |
Strike | NE-SW (41°) [2] |
Displacement | 5 mm (0.20 in)/yr at southern inland limit to 19 mm (0.75 in)/yr at East Coast [2] |
Tectonics | |
Plate | Indo-Australian |
Status | Active |
Earthquakes | Mainly Tectonic |
Type | Intra-arc continental rift |
Movement | Possibly up to 7+ Mw |
Age | Miocene-Holocene |
Volcanic arc/belt | Taupō Volcanic Zone |
New Zealand geology database (includes faults) |
The Taupō Rift is the seismically active rift valley containing the Taupō Volcanic Zone, central North Island of New Zealand.
The Taupō Rift (Taupo Rift) is a 300 km (190 mi) [2] intra-arc continental rift resulting from an oblique convergence in the Hikurangi subduction zone. The present young, modern Taupō Rift is defined by events between 25,000 and 350,000 years [3] and the old Taupō Rift system, which can be defined by a gravity anomaly, is now located more to the north being created between 350,000 and 2 million years and is about 70 kilometres (43 mi) wide. [1] Consensus does not yet exist with regard to the cause of the Taupō Rift's extension or the exceptional volcanic productivity of the associated Taupō Volcanic Zone. Its geology and landforms are of worldwide interest, and it contains multiple significant faults and volcanoes, with some of the volcanoes having potential for worldwide impact. [4]
The recent volcanism of the Taupō Volcanic Zone has been divided into three segments, with a central rhyolitic segment, dominated by explosive caldera associated with more typical Island Arc type andesite-dacite stratovolcanoes in either surrounding segment. In the hundreds of faults and their segments, some have associations with volcanism, but most fault activity is tectonic. [2]
The rift is in that part of the continental Australian Plate associated with the largely underwater Zealandia continental tectonic plate region. The rate of spread of the rift varies from effectively zero, at its southern inland end where the South Wanganui Basin is forming an initial back-arc basin, and volcanic activity has not yet begun, [5] to in the Bay of Plenty as much as 19 mm (0.75 in)/yr. [2] [6] To the north east it is related tectonically to the Havre Trough off the continental shelf which is also an active rift structure. [7] The spread of the rift is associated with the basement graywacke rocks subsiding between the rift walls, so creating grabens infilled with volcanic deposits, sometimes from much higher volcanic mountains than the rift walls. Between 2016 and 2020 there was low volcanic activity in the rift except at Whakaari / White Island, and the areas of maximal satellite measured subsidence were confined to a small areas of about 30 mm (1.2 in)/year near the 2012 Te Māri eruptions site, or the rift geothermal power stations, while from Lake Taupō to the coast subsidence more usually peaked at about 15 mm (0.59 in)/year. [8] The majority of the fault activity is normal faulting. [6] While continental intraarc rifts such as this, and those associated with Mount Aso in Japan, and the Trans-Mexican Volcanic Belt result from a different tectonic process from the more studied intracontinental (intraplate) rifts it has been shown that the Taupō Rift displays all of the three modes of evolution. These are narrowing, lateral migration, and along-strike propagation, as found with intracontinental rifts. [1] The Taupo Rift is widening much faster that other continental intraarc rifts, which might drive this evolution during a relatively short geological timeframe. [1]
In the Bay of Plenty region the current active faults of the old Taupō Rift can align with those of the modern Taupō Rift. This was illustrated by the Edgecumbe Fault and the off sea White Island Fault in the Whakatāne Graben of the rift. [9] The parallel Tauranga Fault Zone to the north represents a now mainly inactive old Taupō Rift margin. [10] Further south, where more of the old Taupō Rift faults appear to be inactive, the active and very complex Taupō Fault Belt is orientated north-north-east. This is trending with the modern Taupō Rift alignment, which is not always quite parallel with the old rift alignment. [1] Beyond Lake Taupō to the south, there is a relatively narrow rifting segment in the Tongariro graben which considerably widens at the Ruapehu graben. South of Ruapehu the rift, and its normal faulting, terminates with east to west faulting in the Taupō Rift termination faults. At the scale of the tectonic plate boundary, the rift trends NE-SW (41 ± 2°) but within New Zealand this trend is presently at 30° south of Lake Taupō and is 55° at the Bay of Plenty coast. [2] A significant change in the mean fault strike occurs just south of the Ōkataina Caldera. [2] The normal fault trends range from N20°E in the south to N45°E in the central and northern sectors. [1] There is good evidence that the orientation of intra-arc strike and extension processes has been maintained for 4 million years in this region of New Zealand. [2]
The modern active rift ranges in width from 15 kilometres (9.3 mi) in the northern Bay of Plenty sector, to 40 kilometres (25 mi) beyond Lake Taupō. Significant faults may be separated by as little as 100 metres (330 ft) in the north but in the south increase to up to 10 kilometres (6.2 mi) separation. There are breaks in the intra-rift fault systems in the recently active central rhyolitic caldera segments at the Taupō Volcano and Ōkataina Caldera. In the later case, the strike of the basaltic dyke of the 1886 eruption of Mount Tarawera follows that of faults to the south and north, confirming other hints that orientation of volcanism is preserved. [2]
The modern Taupō Volcanic Zone starting forming 61,000 years ago but the modern Taupō Rift appears to only have intra-rift fault activity after the immensely disruptive Oruanui eruption. [11]
Earthquake activity in the Taupo Rift exhibits the entire spectrum of behaviour ranging from large, ground rupturing events to swarm activity comprising thousands of small events. In the time since Māori settlement these larger earthquakes can be speculated to have resulted in more indirect loss of life than volcanic activity, although as this is driven by oral tradition reports of hundreds dying in a relatively recent landslip on the Waihi Fault Zone south of Lake Taupō it may not be true. Certainly in the context that the Taupō Volcano has been responsible for the largest eruption of the last 30,000 years being the Oruanui eruption, [11] and the more recent smaller 232 ± 10 CE Hatepe eruption [12] [13] but both eruptions occurred before human settlement, the relative risk of earthquakes versus volcanoes depends upon time scale considered.
The Taupō Volcanic Zone (TVZ) is a volcanic area in the North Island of New Zealand. It has been active for at least the past two million years and is still highly active.
The Kapenga Caldera in New Zealand’s Taupō Volcanic Zone lies in a low land area immediately south of Lake Rotorua through the Hemo Gap in the Rotorua Caldera rim. At some time more than 60,000 years ago Lake Rotorua drained through the Hemo Gap and some of the Kapenga Caldera floor was likely occupied by a lake, that has been called Kapenga.
Ōkataina Caldera is a volcanic caldera and its associated volcanoes located in Taupō Volcanic Zone of New Zealand's North Island. It has several actual or postulated sub calderas. The Ōkataina Caldera is just east of the smaller separate Rotorua Caldera and southwest of the much smaller Rotomā Embayment which is usually regarded as an associated volcano. It shows high rates of explosive rhyolitic volcanism although its last eruption was basaltic. The postulated Haroharo Caldera contained within it has sometimes been described in almost interchangeable terms with the Ōkataina Caldera or volcanic complex or centre and by other authors as a separate complex defined by gravitational and magnetic features.. Since 2010 other terms such as the Haroharo vent alignment, Utu Caldera, Matahina Caldera, Rotoiti Caldera and a postulated Kawerau Caldera are often used, rather than a Haroharo Caldera classification.
The relatively small Rotomā Caldera is in the Taupō Volcanic Zone in the North Island of New Zealand.
The Waihi Fault Zone is a seismically active area of the central North Island of New Zealand whose earthquakes have been associated with significant loss of life.
The Poutu Fault Zone is a seismically active area of the central North Island of New Zealand.
The Hauraki Rift is an active NeS-to NWeSE-striking rift valley system in the North Island of New Zealand that has produced the Firth of Thames and the Hauraki Plains. It is approximately 25 kilometres (16 mi) wide and 250 kilometres (160 mi) long.
Maunga Kākaramea is a 743 metres (2,438 ft) high dacite volcano located between Rotorua and Taupō in the North Island Volcanic Plateau. It has multiple steaming features and a picturesque crater lake reached by a short walk from the nearest road and has a nearby geothermal area.
Maungaongaonga is an 825 metres (2,707 ft) high dacite volcano located between Rotorua and Taupō in the North Island Volcanic Plateau. The area of the mountain is a scenic reserve and some of its southern slopes are highly geothermally active.
The Paeroa Fault is a seismically active area in the Taupō District, Waikato Region of the central North Island of New Zealand.
The Ngapouri-Rotomahana Fault is a seismically and volcanically active area of the central North Island of New Zealand.
The Ōkāreka Embayment is a volcanic feature in Taupo Volcanic Zone of New Zealand. Its most significant recent volcanic eruption was about 15,700 years ago and this deposited the widespread Rotorua tephra that reached beyond Auckland.
The Horohoro Fault is in the old Taupō Rift of the central North Island of New Zealand and is associated with the spectacular Horohoro cliffs.
The Taupō Fault Belt contains many almost parallel active faults, and is located in the Taupō Rift of the central North Island of New Zealand geographically between Lake Taupō and the lakes of Rotorua, Tarawera, Rotomahana and Rerewhakaaitu. The potential active fault density is very high, with only 0.1 to 1 km separating the north-east to south-west orientated normal fault strands on detailed mapping of part of the belt. The Waikato River bisects the western region of the belt.
The Tikitere Graben is a intra-rift graben in the North Island of New Zealand that contains the Ohau Channel, which drains Lake Rotorua into Lake Rotoiti with a minimal drop between the lakes.
The Coromandel Volcanic Zone (CVZ) is an extinct intraplate volcanic arc stretching from Great Barrier Island in the north, through the Coromandel Peninsula, to the Kaimai Range in the south. The area of transition between it and the newer and still active Taupō Volcanic Zone is now usually separated and is called the Tauranga Volcanic Centre. Its volcanic activity was associated with the formation and most active period of the Hauraki Rift.
Much of the volcanic activity in the northern portions of the North Island of New Zealand is recent in geological terms and has taken place over the last 30 million years. This is primarily due to the North Island's position on the boundary between the Indo-Australian and Pacific Plates, a part of the Pacific Ring of Fire, and particularly the subduction of the Pacific Plate under the Indo-Australian Plate. The activity has included some of the world's largest eruptions in geologically recent times and has resulted in much of the surface formations of the North Island being volcanic as shown in the map.
The Manawahe Fault line is a seismically active area in the Bay of Plenty Region of the central North Island of New Zealand with the potential to be involved with other faults in an Mw7.0 event.
The Whakatāne Graben is a predominantly normal faulting tectonic feature of the northeastern aspect of the young, modern Taupō Rift in New Zealand. At the coast it is widening by about 7 mm (0.28 in)/year. This very geologically active graben was the site of the 1987 Edgecumbe earthquake, which caused up to 2 m of land subsidence. The discontinuity in the Taupō Volcanic Zone's faults imposed by the highly active Ōkataina Volcanic Centre, geography and geology mean the graben is usually regarded as including the actively expanding and lowering region onshore extending towards the coast. Some scientists have limited the Whakatāne Graben to only the offshore continuation of the Taupō Rift.
The Matata Fault zone is a seismically active area in the Bay of Plenty Region of the central North Island of New Zealand with potential to rupture as part of an Mw 7.0 event.