es ault kaimai -...
TRANSCRIPT
1 million years ago to present
DepositionErosion
Deposition
Covering upLater more explosive rhyolite eruptions in the Rotorua area (and
possibly within the Tauranga Basin) spread vast amounts of hot
rocks and ash – known as ignimbrite – out over large parts of
the land. Some ignimbrite deposits were relatively small - like the
Aongatete Ignimbrite which covered this area. Others were much
larger, such as the Waiteariki Ignimbrite which is up to 220 metres
thick. Local rhyolitic eruptions also formed hills like the Kaimai
Dome at the headwaters of the Wairoa River and Mt Maunganui
(Mauao) on the coast.
Lifting upStarting about 7 million years ago, massive tearing in the Earth’s
crust made what is now called the Hauraki Fault. Although it
took millions of years to form, most movement happened about
1-2 million years ago when the Kaimai volcanos on the east of the
Hauraki Fault were uplifted (in places up to 4 kilometres higher
than the west). As well as creating the mountain range, the
faulting also tilted the Waiteariki Ignimbrite to form the
gently-inclined fertile plateau of the Tauranga Basin.
Filling inOver the last million + years, the low land in and around what is
now Tauranga Harbour has been filled slowly with river
sediments, swamp deposits, dunes and volcanic ash up to 50 m
thick in places.
The low areas west of the Hauraki Fault were also filled up with
ignimbrites and sediments to form the Hauraki Plains.
TheKaimai
Range Making mountainsThe Kaimai Ranges are made up of a series of volcanos (mostly
andesitic-dacitic cones) which erupted between 4 and 5.6 million
years ago. They are the southern end (and youngest) of a line of
progressively older volcanos which extend up to the northernmost
tip of the Coromandel Peninsula.
3.9 - 2 million years ago
Aongatete ignimbrite
Waiteariki ignimbrite
coast
2 - 1.2 million years ago
Ignimbrite rock sample
Hauraki Fault
5.6 - 4 million years ago
Greywacke basement rocks
Kaimai Volcanos
Fact A New Zealand geologist
named this type of rock –
it means ‘fiery rock dust’
Ignimbrite
Andesite rock sample
FactThe names comes from ‘The
Andes’ in South America, where
this type of rock is common
Andesite
Ha
ura
ki P
lain
sH
au
rak
i F
au
lt
Ka
ima
i R
an
ges
Tuapiro F
ault
Whakamarama PlateauTilted 3-5o
YOU ARE HERE
Tauranga
Kaimai Dome
Mamaku Plateau
Wairo
a Riv
er
Aongatete RiverMount Maunganui
Papamoa Range
The big picture