Ngakuru Graben
| Ngakuru Graben | |
|---|---|
| Whirinaki Valley | |
.svg)  Ngakuru Graben   Ngakuru Graben Ngakuru Graben (North Island) | |
| Length | 19 km (12 mi) approximately |
| Width | (4.5 km (2.8 mi)) 15 km (9.3 mi) Much current work as of 2022 refers to wider width |
| Geology | |
| Type | intra-rift garben |
| Age | 61,000 years |
| Geography | |
| Country | New Zealand |
| State/Province | Waikato |
| Coordinates | 38°19′05″S 176°12′29″E / 38.318°S 176.208°E[1] |
| River | Totara Stream, Rehi Stream, Whirinaki Stream, Rotohouhou Stream |
The Ngakuru Graben is an area of tectonic ground subsiding as originally defined between the Ngakuru Fault to the east and the Whirinaki Fault in the west both in the Taupō Fault Belt.[2] It was originally defined in 1959[3] but many other geological terms for local features are no longer in use, and some were misinterpretations. Within this 4.5 km (2.8 mi) wide Ngakuru Graben are also to the west the Maleme Fault (Zone), which as a zone also contains the Mangaete/Lakeside Fault and to the east the Hossack Road Fault and the Te Weta Fault.[2] Some authors have defined a wider 15 km (9.3 mi) wide area so as to include all of the low-lying areas associated with the Taupō Fault Belt immediately south of Rotorua so this includes the more eastern Paeroa and Ngapouri Faults and much of the Kapenga Caldera.[4] Unhappily both definitions as to width seem current in the literature.
The tectonic activity is driven by the ground subsiding at a rate of 3–4 mm/yr since 61,000 years ago with largely orthogonal rifting associated with subduction and the clockwise rotation of the northern North Island allowing the rift to open.[2]
References
- ^ NZTopoMap
- ^ a b c Loame, Remedy Charlotte (2016). Using a tephrostratigraphic framework to determine the past 40,000 yrs of fault rupture and paleohydrothermal activity on the east strand of the Whirinaki Fault, Ngakuru Graben, central Taupo Volcanic Zone (PDF) (Thesis).
- ^ Grindley, G. W., 1959, Geological Map NZ 1:63360,Sheet 8, Waiotapu. DSIR.
- ^ Villamor, Pilar; Nairn, Ian; Seebeck, Hannu (2015). "FIELDTRIP 2 EARTHQUAKES AND ERUPTIONS AT OKATAINA VOLCANIC CENTRE" (PDF). Retrieved 30 August 2022.
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