Bali Hai - Ambae...for a generation or more it has conjured visions of mystique, of a magical primitive Paradise. Ambae is an exceptionally beautiful island and its legendary disappearing act is quite true. When seen from the east coast of Santo, the island is a clear blue pyramid rising from the ocean in the early morning light. But as the sun climbs higher, except for rare, clear days, the island quickly disappears behind a glare of sea haze.

Ambae's pyramid shape is due to its volcanic origins. By far the largest of the Vanuatu volcanoes (its base is 3,000m below Sea Level!) after a slumber of 400 years, Ambae shocked its inhabitants by awakening in 1991.

Twin crater lakes adorn this jungle isle. The distinctive bright blue and green lakes are rarely see, for the tall island (4,907 ft) is perennially capped in rain clouds, a micro climate formed in part by the verdant tropical rainforest. On the few days in the year the lakes can be seen from the air, they are stunning jewels nestled in a verdent setting.

But on July 13, 1991, a Vanair (domestic airline) pilot was more than a little shocked to see three unusual "boiling" areas with large bubbles (10 m in diameter) and burned vegetation along the edges of Lake Voui. The pilot had last seen the area green and lush just two months before.

On 24 July 1991, an aerial survey revealed three areas of discolored water in Lake Voui, and burned vegetation, most likely by sulfur dioxide discharge, all the way up to the crater rim, 120 m above the lake water. Unnoticed by island residents, this event marked the end of a long time of quiescence.

Over the next three years an increase in the number and intensity of earthquakes and unusual frothing and high temperatures of the lake water were sufficient for an evacuation plan to be set in place. More than 3,500 people live within 10 kilometers of the vent. Mud flows (lahars) had been known to wipe out entire villages, so the warnings were taken very seriously. Evacuation plans included moving inhabitants from those areas of the island that might fracture in the event of a full scale eruption (see the description of Ambrym eruption in 1913), to outright removal from the island.

Although the lake temperatures declined and activity seemed to quieten, the inhabitants and the National Disaster office were not fooled into thinking all was well. Then on March 1, 1995 a VANAIR pilot noted Lake Voui was calm with gas escapes in numerous places, but the following day, the lake was steaming all over, bubbling up in the centre. Its surface was rough and blowing out black sediments. Early in the morning of March 3, people of Santo, 70 km away, saw a gas plume rising up to 2 - 3 km above Lake Voui. Simultaneously, crustal seismicity (shallow, localised earthquakes associated with volcanic activity) was recorded.

From 4 to 6 March, geophysicists from ORSTOM, Port-Vila, moved to Ambae and recorded strong and continuous tremor at Ndui Ndui, about 9 km NW from the main crater. Their readings indicated a possible imminent eruption with a VEI of 3.5 to 4. The chances of eruption? 70%.

Following a few false alarms, Ambae soon proved, once again, how inexact a science predicting volcanic eruptions is. It has fallen into a slumber and has remained quiescent until this writing (early 1999), however Ambae, Bali Hai, is currently considered the most dangerous of Vanuatu's volcanoes.

Update: Ambae again erupted in December 2005. For more information on this volcano, contact Esline Garae, Vanuatu's manager of geology hazards.