Rotomā Caldera
{{Short description|Volcanic caldera in the North Island of New Zealand}}
{{Use New Zealand English|date=April 2024}}
{{Use dmy dates|date=June 2022}}
{{broader|Ōkataina Caldera}}
{{Infobox mountain
| name = Rotomā Caldera
| other_name= Rotoma Caldera, Rotomā Embayment
| photo =Lake Rotoma, Bay of Plenty, New Zealand, 3 April 2008.jpg
| photo_caption =Lake Rotomā fills the Rotomā Caldera
| map=New Zealand#North Island
| elevation_m =316
| elevation_ref =
| prominence =
| location = North Island
| country = New Zealand
| region = Bay of Plenty
| coordinates = {{coord|38|05|S|176|35|E|format=dms|display=inline,title}}
| range_coordinates =
| topo =
| type = Caldera
| age = approximately 9,000 years
| width = {{convert|5|km|abbr=on}}
| length =
| volcanic_region = Taupō Volcanic Zone
| last_eruption = 7412 BCE
| access =State Highway 30 (New Zealand)
}}
File:Paeroa-Ngapouri-Rotomahana Faults.jpg
The relatively small Rotomā Caldera (also known as Rotomā Embayment,{{cite journal|first1=Ery C. |last1=Hughes |first2=Sally |last2=Law |first3= Geoff |last3=Kilgour |first4= Jon D. |last4=Blundy |first5= Heidy M. |last5=Mader |title=Storage, evolution, and mixing in basaltic eruptions from around the Okataina Volcanic Centre, Taupō Volcanic Zone, Aotearoa New Zealand |journal=Journal of Volcanology and Geothermal Research |volume=434 |year=2023 |issue=107715 |ISSN=0377-0273 |doi=10.1016/j.jvolgeores.2022.107715 |url=https://www.sciencedirect.com/science/article/pii/S0377027322002463)|hdl=20.500.11820/9f5c151c-1f2e-47ed-a264-7649eacdf669 |hdl-access=free }} Rotomā volcanic complex, and spelled Rotoma) is in the Taupō Volcanic Zone in the North Island of New Zealand.
Geography
The Rotomā Caldera is located halfway between the city of Rotorua and town of Whakatāne, with its in filling Lake Rotomā being the easternmost in the chain of three volcanic lakes to the northeast of Lake Rotorua. The other two are Lake Rotoiti and Lake Rotoehu.
=Geology=
The Rotomā Caldera is immediately to the northeast of the area previously called the Haroharo volcanic complex, and now known as the Haroharo vent alignment."[https://www.gns.cri.nz/Home/Learning/Science-Topics/Volcanoes/New-Zealand-Volcanoes/Volcano-Geology-and-Hazards/Okataina-Volcanic-Centre-Geology Okataina Volcanic Centre Geology]," GNS science. Retrieved 11 June 2022. This is now regarded as part of the much larger Ōkataina Caldera ( Ōkataina Volcanic Centre).McKinnon, M., "[https://teara.govt.nz/en/map/15134/okataina-caldera-and-its-neighbours Okataina caldera and its neighbours]," Te Ara - Encyclopedia of New Zealand, 1 May 2015. Retrieved 11 June 2022. It has been usually classified as part of this volcanic structure,{{cite journal
|last1=Smith
|first1=Victoria
|last2=Shane
|first2=Phil
|last3=Nairn
|first3=I.A.
|last4=Williams
|first4=Catherine
|date=2006-07-01
|pages=57–88
|title=Geochemistry and magmatic properties of eruption episodes from Haroharo linear vent zone, Okataina Volcanic Centre, New Zealand during the last 10 kyr
|volume= 69
|issue=1
|doi=10.1007/s00445-006-0056-7
|journal=Bulletin of Volcanology
|url=https://www.researchgate.net/publication/226293147_Geochemistry_and_magmatic_properties_of_eruption_episodes_from_Haroharo_linear_vent_zone_Okataina_Volcanic_Centre_New_Zealand_during_the_last_10_kyr
}}{{Cite journal |last1=Cole |first1=J. W. |last2=Spinks |first2=K. D. |s2cid=131562598 |year=2009 |title=Caldera volcanism and rift structure in the Taupo Volcanic Zone, New Zealand |publisher=Geological Society |place=London |journal=Special Publications |volume=327 |pages=9–29 |doi=10.1144/SP327.2 |url=http://sp.lyellcollection.org/cgi/content/abstract/327/1/9 |issue=1|bibcode = 2009GSLSP.327....9C |url-access=subscription }} but given the evidence that it is a region of structural collapse beyond the Ōkataina Caldera rim is perhaps best called an embayment. It is associated with the northern fault boundary zone (Rotoehu Fault, Manawahe Fault, North Rotomā Fault, Braemar Fault, Mangaone Fault) in the Whakatāne Graben part of current rift activity in the Taupō Volcanic Zone. The caldera is likely overlying the former drainage valley that historically Lake Rotorua used before the Rotoiti eruption of the Ōkataina Caldera 47,400 ± 1500 years ago.{{Cite journal |last1=Gilgour |first1=G.N. |last2=Smith |first2=R.T. |journal=New Zealand Journal of Geology & Geophysics |year=2008 |volume=51 |pages=367–378 |title=Stratigraphy, dynamics, and eruption impacts of the dual magma Rotorua eruptive episode, Okataina Volcanic Centre, New Zealand|url=http://web.gps.caltech.edu/~jstock/Ge121a/nzjgg_2008_026_Okataina.pdf}} The Rotomā volcano's most prominent feature Lake Rotomā was formed within the Rotomā caldera when lava flows following a large crater explosion blocked its outlet. The major eruption episodes were about 7412 BCE with about {{convert|8|km3|abbr=on}} of material erupted from 3 different magmas from several different vents. This eruptive sequence was associated in time with ruptures in the Manawahe Fault about {{convert|10|km|abbr=on}} to the north-east.{{cite journal|first1=P. |last1=Villamor|first2= N.J. |last2=Litchfield|first3= D. |last3=Gomez|first4= F. |last4=Martin |first5= B. |last5=Alloway |first6= K. |last6=Berryman|first7= K. |last7=Clark|first8= W. |last8=Ries|first9= A. |last9=Howell |first10= B. |last10=Ansell |title=Fault ruptures triggered by large rhyolitic eruption s at the boundary between tectonic and magmatic rift segments: the Manawahe Fault, Taupo Rift, New Zealand |journal= Journal of Volcanology and Geothermal Research | year=2022 |doi= 10.1016/j.jvolgeores.2022.107478 |url=https://www.sciencedirect.com/science/article/pii/S0377027322000099|hdl=2292/59828 |hdl-access=free }} It is known that the changes in vegetation following the eruption, while significant, were short-lived. Pre-eruption forest and mire vegetation recovering to former levels within about 106 years.{{Cite web|last1=Giles|first1=Teresa Mary|title=Volcanic emissions and distal palaeoenvironmental impacts in New Zealand|url=https://pearl.plymouth.ac.uk/bitstream/handle/10026.1/2176/TERESA%20MARY%20GILES.pdf|year=1999|access-date=2022-06-19}}