Volcanoes - Ministry of Civil Defence and Emergency Management

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This article outlines how the ‘Contingency Plan
for the Auckland Volcanic Field’ and other preparedness
measures provide a framework to manage these unique
circumstances, and minimise the risk to Auckland
communities.
THE AUCKLAND VOLCANIC FIELD
The earliest eruptions of the monogenetic
Auckland Volcanic Field (AVF) are estimated to have
occurred 150,000 years ago. Since this time, another 49
basaltic volcanoes have been created. During the last
20,000 years eruptions have been more frequent with
events occurring, on average, once every 1000 years.
Therefore there is a 5% probability of an eruption from
the AVF within the next 50 years. The most recent
and largest eruption occurred approximately 750 years
ago. It created Rangitoto Island, a volcano that erupted
approximately 1/3 of the total magma extruded from the
Auckland Volcanic Field.
There are no written or scientific records of
an eruption from the Auckland Volcanic Field, and
therefore limited knowledge of the length of warning
that eruption precursors (eg. volcanic earthquakes) will
give. Geological evidence indicates that volcanic activity
will give rise to a number of hazards which will have
minor to severe impacts both in terms of damage and
geographic extent.
VOLCANIC HAZARDS
The areal extent of the AVF Volcanic hazards,
described in Table 1, may be greater should there be
more than one eruption vent active at a time. Vents in a
multi-vent episode are expected to develop within a few
kilometres of one another.
The highly developed nature of metropolitan
Auckland, and the reliance of its residents on
continuance of infrastructural services, makes this city
vulnerable to eruptive events.
A number of preparedness measures have been
established to reduce the risk to Auckland communities
from an Auckland Volcanic Field Eruption.
READINESS MECHANISMS
Preparedness mechanisms established to
minimise risk from an AVF eruption include:
• Seismic Monitoring: Monitoring of the Auckland
Volcanic Field using a network of permanent
seismometers.
• Volcanic Contingency Plan: Establishes a framework
to enable a coordinated civil defence emergency
management response and identifies roles,
responsibilities and actions for organisations that
will contribute to response to, and recovery from, an
eruption.
Auckland, with the Auckland Harbour Bridge in the foreground is home to about 1.3 million people. Photo: GNS Lloyd Homer.
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TEPHRA
June 2004