Alexandra Volcanic Group
Extinct volcanoes in the Waikato Region, New Zealand / From Wikipedia, the free encyclopedia
The Alexandra Volcanic Group (also known as Alexandra volcanic lineament or Alexandra Volcanics) is a chain of extinct calc-alkalic basaltic stratovolcanoes that were most active between 2.74 and 1.60 million years ago but is now known to have had more recent activity between 1.6 and 0.9 million years ago.[1] They extend inland from Mount Karioi near Raglan with Mount Pirongia being the largest,[3] with Pukehoua on the eastern slopes of Pirongia, Kakepuku, Te Kawa, and Tokanui completing the definitive lineament. The associated, but usually separated geologically basaltic monogenetic Okete volcanic field (also known as the Okete Volcanic Formation or Okete Volcanics), lies mainly between Karioi and Pirongia but extends to the east and is quite scattered.
Alexandra Volcanic Group (including Okete volcanic field) | |
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Highest point | |
Coordinates | 37°59′35″S 174°59′0″E[1] |
Geography | |
Geology | |
Age of rock | Miocene to Pliocene(2.74–0.9 Ma)[2] |
Mountain type | Volcanic field |
Type of rock | Basalt |
Last eruption | 0.9 Ma[1] |