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will have low Q unless the supply rate is particularly high. Estimates of eruptive
volumes and Q can also be used to give rough estimates of age. In the LVF, the
total volume of erupted magma is estimated to be approximately 12 km 3 . This
estimate must be regarded as a minimum value as eroded material is neglected
in the calculation. Some cinder cones and maars, and most of the tephra pro-
duced during explosive eruptions, are also usually neglected. The age of the LVF,
assuming a constant Q over the lifetime of the volcanic field and no major hia-
tus in volcanism, agrees closely with estimates based upon maar morphology
(14 000--40 000 years BP).
Pollen records
Pollen records, in association with geologic records, can help to identify
major episodes of volcanism. Stratigraphic analysis incorporating tephrostrati-
graphic records in the North Island of New Zealand show that the region has
experienced a violent volcanic history throughout the Quaternary. The main vol-
canic centres are Okataina, Taupo, Maroa and Mayor Island. The Kaharoa tephra
layer dated to 665 ± 15 years BP highlights one of the more recent of these major
eruptive episodes. The tephra layer was ejected from the Tarawera volcano in the
Okataina Volcanic centre and consists of a sequence of fine ash overlying coarse
ash. Giles et al .(1999)foundthat this eruption and others like it have had a pro-
found effect on New Zealand vegetation communities. Immediately following
deposition of the tephra layer, the pollen record indicates significant distur-
bances. The levels of broken and degraded pollen grains increase and there is a
sharp rise in pollen from species that are assumed to be invaders following the
disturbance. There is also an increase in pollen levels from some tree species that
thrive on fresh volcanic surfaces. Likewise, there is a decline of previously domi-
nant species following the deposition of the tephra layer. Other mechanisms for
thedramatic change in vegetation communities based upon the pollen record
cannot specifically be ruled out; however, the scale and nature of the change
strongly suggests that volcanic eruptions are the most likely cause.
Conclusion
Volcanic eruptions leave an indelible imprint in the landscape, both
human and natural. The classic studies of Pompeii and Herculaneum after the
eruption of Vesuvius are well documented, but other investigations such as that
by Ford andRose(1995) where they examined volcanic material within pottery
made by the Mayans in central America also throw light on the nature of vol-
canism in that region. Likewise, mythology offers glimpses into major volcanic
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