The Maroa Caldera (Maroa Volcanic Centre) is approximately 16 km × 25 km (9.9 mi × 15.5 mi) in size and is located in the north-east corner of the earlier Whakamaru caldera in the Taupo Volcanic Zone in the North Island of New Zealand.

Maroa Caldera
Maroa Caldera approximate location and boundaries contained within the older Whakamaru Caldera. The Ohakuri Caldera which had a paired eruption with the Rotorua Caldera is to its north and was not recognised as a separate caldera historically. To its west is the oldest Mangakino Caldera of the old Taupō Rift (yellow shading). Also shown is the modern Taupō Rift (red shading), Hauraki Rift (purple shading) and landmarks of Lake Taupō and Lake Rotorua
Highest point
Peak	Maroanui
Elevation	897 m (2,943 ft)
Coordinates	38°31′11″S 176°01′19″E
Dimensions
Length	25 km (16 mi)[1]
Width	16 km (9.9 mi)[1]
Geography
North Island
Country	New Zealand
Region	Waikato
Range coordinates	38°25′12″S 176°4′48″E
Geology
Age of rock	300,000 to 14,000 years[2]
Mountain type	Caldera
Volcanic region	Taupō Volcanic Zone
Last eruption	14,000 years ago[1]
Climbing
Access	State Highway 1 (New Zealand)

Geography

Its northern rim is to the south of the Waikato River at Atiamuri. At Atiamuri the Ohakuri Caldera which had a paired eruption with the Rotorua Caldera is to its immediate north. The eastern boundary is also defined by the present Waikato River and it extends as far south as probably opposite Orakei Korako on the river. The southern boundary is somewhat ill defined given the subsequent deep deposits from the Taupō Volcano but includes a number of domes of which the highest is Maroanui at 897 metres (2,943 ft).

Eruptive history

The Maroa Caldera's last major eruption produced 140 km³ (33.6 cu mi) of tephra about 230,000 years ago (230 ka).[2] Its earliest eruption was about 300 ka with decreasing frequency and volume to as recently as 16.5ka[3] when an eruption of about 0.25 km³ (0.1 cu mi) occurred from the Puketarata volcanic complex (38°33′02″S 176°03′16″E to distinguish from another older volcano of this name near Te Kawa).[3][4] The caldera is now mainly dome lava in filled.[1] In summary going back in time: [1]

• 16,500 years ago Puketarata tuff ring formed with total volume of 0.25 km³ (0.060 cu mi)[4] in a complex series of eruptions including maar formation[3]
• 229,000 to 196,000 Pukeahua deposits and dome building
• 220,000 unclear where Mokai ignimbrite that outcrop in some of Maroa area comes from
• 229,000 ± 12,000 Atiamuri deposits from northern Maroa
• 251,000 ± 17,000 onward two large parallel dome complexes developed
• 256,000 ± 12,000 Orakonui pyroclastics from a central Maroa source
• 272,000 ± 10,000 Putauaki pyroclastics from a central Maroa source
• 275,000 to 240,000 years ago small-scale pyroclastic eruptions
• 283,000 ± 11,000 Korotai deposits from northern Maroa
• 305,000 ± 17,000 oldest Maroa dome

References