Volcano of the week!

16/12/2013-22/12/2013

This week’s ‘Volcano of the Week’ is:

Yasur

Location: Tanna, Vanuatu

Type: Stratovolcano

Elevation: 1184 ft, 361 m

Last Eruption: 2013 (continuing)

Status: ACTIVE

Details:

Yasur is situated on an Indo-Australian and Pacific subduction zone and is one of the most accessible active volcano in the world. It has a pyroclastic cone with a crater measuring 400m in diameter. Although some uncertainty lies in the dates, according to radiocarbon dating, eruptions have occurred in 0550, 0850 (± 300 years) and 1150. Since the first witnessed eruption by Captain Cook in 1774, Yasur has been active. Activity has been of Vulcanian or Strombolian in nature and 2 or 3 on the VEI scale.

Shown below are a few photos of Yasur.

                                Photo by Tom Pfeiffer: Lava bombs at Yasur

                                Photo by Tom Pfeiffer

The most recent activity at the volcano began on 3^rd November when a new phase of ash emission started. It is likely that this ash emissions will continue for weeks to come, however activity remains low and the current Alert level remains at 1. Vanuatu’s Geohazard Observatory has advised villages in the Red and Yellow Hazard Zones to expect ash falls during this ongoing activity.

Earlier in 2013 Yasur also had increased activity. Ash fall was widespread across the island of Tanna and affected numerous nearby villages, lava bombs were ejected and an eruption plume rose to a height of 1.8km affecting the aviation industry in New Caledonia,located 430 km west. A 500 m exclusion zone was put in place to restrict visitors. The Alert level was increased to 3 in May and July.

Yasur has been associated with various hazards in past eruptions including; tephra, volcano bombs, pyroclastic flows and ash fall. A number of hazard and risk maps have been created by scientists to show the potential impacts from future cataclysmic eruptions. An example is shown below.

Hazard zones developed for the potential impacts from Yasur (Source: Monzier and Robin, 1996)

When activity is low, it is possible to go near the crater of the volcano. Since this is a major tourist attraction, risk reduction measures have been put into place. When activity increases Vanuatu’s Geohazard Observatory increases the Alert level so no tourists can enter the restriction zones. The table below shows Vanuatu’s Volcano Alert Levels used by the Observatory.

VVAL	Frequently Active Volcano Group (Yasur, Lopevi, Ambrym)	'Dormant' Volcano Group (Ambae, Gaua, Vanua Lava)
Lvl.?	Insufficient Monitoring to make assessment
Lvl.0	Normal low-level activity.	Normal, quiet.
Lvl.1	Increased activity, danger near crater only.	Signs of awakening.
Lvl.2	Moderate eruptions, danger close to the volcano vent, within parts of Volcanic Hazards Map Red Zone.	Confirmation of awakening, Minor eruptions and danger near to crater.
Lvl.3	Large eruption, danger in specific areas within parts of Volcanic Hazards Map Red and Yellow Zones.	Moderate to large eruption, danger in areas near crater and along main stream valleys.
Lvl.4	Very large eruption, island-wide danger (including areas within Red, Yellow and Green Zones).	Very large eruption, island-wide danger and potential impacrs on neighbouring islands.

Source: Vanuatu’s Geohazard Observatory http://www.geohazards.gov.vu/

Vanuatu’s Geohazard Observatory has also created a hazard map shown below. The high, medium and low hazard zone categories are shown in red, yellow and green as shown on the legend.

Source: volcanic.massey.ac.nz