Coromandel Volcanic Zone
The Coromandel Volcanic Zone (CVZ) was a formerly active volcanic field on the North Island of New Zealand .
geography
The area of the Coromandel Volcanic Zone extends from the Great Barrier Island over the Coromandel Peninsula to the southern end of the Kaimai Range and includes the islands east of the Coromandel Peninsula such as Cuvier Island , Mercury Islands , The Aldermen Islands , Slipper Island , Mayor Island and Motiti Island .
The island of Little Barrier Iceland , although volcanic origin, 18 km west of Great Barrier Iceland location is so far a special feature and is not to Coromandel Volcanic Zone counted, as they in the Hauraki Rift is (ditch) and has a different history.
geology
The geological history of the Coromandel Volcanic Zone can be divided into five sections. The first two phases affect New Zealand as a whole, when the base rock of the greywacke formed and New Zealand with Zealandia separated from the supercontinent Gondwana around 80 million years ago and was mostly below sea level around 30 million years ago.
In the third phase, which began around 25 million years ago, the area around today's Coromandel Peninsula came into the tension field of the two converging continental plates , the Pacific plate and the Australian plate , resulting in volcanic activity, which began 18 million years ago, initially in the area of Great Barrier Island and in the northern part of the Coromandel Peninsula and lasted around 14 million years with the formation of andesite rocks.
In the fourth phase, which began 12 million years ago, the chemical composition of the emerging lava slowly changed , which included the formation of rhyolite . The volcanic activities, which were comparable to those of the Taupo Volcanic Zone with its hydrothermal activities of today, also migrated to the east side of the Coromandel Peninsula , where rhyolite cores from former volcanoes can still be found today.
In the fifth and final phase, local volcanic fields formed in Northland , in the Auckland and Mercury Islands area with basalt rock.
Evidence of former volcanoes
Calderas
On the Coromandel Peninsula there are calderas of former volcanoes in four places , in Waihi , where gold and silver are mined in the Martha Mine , near Whiritoa the Tunaiti caldera , northwest of Whangamata the Wharekawa caldera and the Kapowai caldera , west of Tairua .
Likewise, a 2.0 km to 2.8 km wide caldera of the 320 m high Tutaretare can be visited on Mayor Island .
Lava domes
A well-known lava dome in New Zealand is Mount Maunganui , near Tauranga . With a height of 231 m , the core of the former volcano, located directly at the entrance to Tauranga Harbor , is visible far beyond the coast and has become a symbol of Tauranga .
Another lava dome can be seen in Tairua on the east coast of the Coromandel Peninsula . The mountain called Mount Paku , which lies directly at the entrance to Tairua Harbor , has two peaks of former volcanic cores, of which the higher has a height of 179 m .
Thermal springs
One of the most famous hot springs on the Coromandel Peninsula is located on Hot Water Beach , 12 km southeast of Whitianga . In some places right on the beach, water up to 64 ° C rises through the sand to the surface and mixes with the seawater. Tourists like to create small depressions in the sand there and use the warm water to swim and linger.
Another well-known thermal spring with pools up to 39.5 ° C is located in Athenree .
literature
- RM Briggs, BWJ Fulton : Volcanism, structure, and petrology of the Whiritoa-Whangamata coastal section, Coromandel Volcanic Zone, New Zealand: Facies model evidence for the Tunaiti caldera . In: New Zealand Journal of Geology and Geophysics . Volume 33 , 1990, pp. 623–633 , doi : 10.1080 / 00288306.1990.10421380 (English, online [PDF; 1.5 MB ; accessed on May 31, 2018]).
- Peter Ballance : New Zealand geology: an illustrated guide (= Miscellaneous Publication No. 148 ). Geoscience Society of New Zealand , Auckland 2009, ISBN 978-0-473-41925-7 (English, online [PDF; 23.5 MB ; accessed on May 31, 2018]).
Individual evidence
- ^ Ballance : New Zealand geology: an illustrated guide . 2009, p. 105 .
- ^ Ballance : New Zealand geology: an illustrated guide . 2009, p. 115 .
- ↑ a b Ballance : New Zealand geology: an illustrated guide . 2009, p. 107 .
- ^ Ballance : New Zealand geology: an illustrated guide . 2009, p. 108-110 .
- ↑ Briggs, Fulton : Volcanism, structure, and petrology of the Whiritoa-Whangamata coastal section, Coromandel Volcanic Zone ... . 1990, p. 624 .
- ↑ Coordinates and longitudes were determined using Goggle Earth Pro Version 7.3.1.4507 on May 31, 2018
- ↑ Topo250 maps . Land Information New Zealand , accessed May 31, 2018 .