THE ORIGIN OF PACIFIC ISLANDS

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SOUTH PACIFIC APPLIED GEOSCIENCE COMMISSION (SOPAC)

Suva, Fiji Islands

Press Release August 27, 1999

Russell Howorth, SOPAC Program Manager

Much of the discussion at the recent Forum Economic Ministers Meeting (FEMM) held in Apia, Samoa, focused on the islands economic reform process. Listening to these discussions had my mind wandering from "the economic reform process" to the "physical formation process" and the origins of Pacific Islands.

Pacific Islands, literally meaning peaceful islands, is far from a reality, when we study the origins of many of them. Many islands rising out of the Pacific Ocean owe their origins to one of the most physically energetic and often awesome and destructive processes of Mother Nature – volcanic activity. And what better example than Savai'i in Samoa.

The volcanic heritage of the islands in the Pacific is vividly illustrated by reference to the one country which takes it name from this very heritage and the host of the 1999 FEMM, namely Samoa. The name comes from the words sa ia moa in the Samoan language. According to Samoan legend, "the rocks cried to the Earth, and the Earth became pregnant. Salevao, the god of rocks, observed motion in the moa, or center of the Earth. The child was born and named sa ia Moa from the place it was seen moving."

Historic eruptions on Savai'i are not uncommon. Several periods of lava flows in different parts of the island are known to have occurred over the past three hundred years. Early settlers established that Samoan tradition recorded extensive eruptions about 1760 in the northwest of the island from Maunga Afi crater and destroyed several coastal villages. In 1902 a small eruption occurred from Maunga Mu just to the east of Afi.

The latest period of activity began on August 5 1905. The lava erupted from Matavanu crater at a height of 600 meters (1,980 feet) high up on the north side of the island and flowed 20 kilometers (12 miles) down to the coast and into the sea.

The lava reached the coast in December of that year. The beginning of 1906 saw a dramatic increase in activity and lava flowed into the sea more or less continuously for the following five years.

Four coastal villages were evacuated before being destroyed. The villages have never been rebuilt and the villagers relocated themselves on nearby Upolu. Fumaroles, or steam vents, depositing sulfur marked the latter stage of activity, the sulfur crystals deposited were still being collected by the villagers as recently as the past ten years for medicinal use.

Eyewitness accounts indicated that where the coast was bordered by coral reef, the lava quickly filled up the lagoon and flowed out over the reef, thereby extending the coastline seawards. Much lava flowed out into deep water through gaps in the reef during the years of the eruption.

Savai'i is the largest of the two major islands in Samoa. It has a population of nearly 45,000 all living in coastal villages. Beautiful pocket beaches of white sand derived from the reef contrast with the black volcanic basalt lava flows, which form the headlands that separate the beaches.

The island of Savai'i represents the uppermost part presently exposed above sea level of Savai'i Volcano, a huge pile of volcanic rocks built upon the surrounding deep sea floor from a depth of 4,000 meters (13,200 feet) below present sea level over the past two million years. The island presently rises to a height of 1,858 meters (6,132 feet) at Mount Silisili, making the total height of the volcano nearly 6,000 meters (20,000 feet).

By comparison, two of the largest active volcanoes in New Zealand are Mt. Ruapehu, which rises to a height of close to 2,000 meters (6,600 feet) from the surrounding Central Volcanic Plateau, and Mt. Taranaki (Egmont), which rises approximately 2,500 meters (8, 250 feet) from the surrounding coastal lowland.

Many active volcanoes occur in the Pacific, in what is commonly referred to as the Pacific Rim of Fire, which surrounds the Pacific Ocean. Hawai‘i and Savai'i are not in the Rim of Fire. Typical of the more violent eruptions of volcanoes on the Pacific Rim is at Rabaul, at the eastern end of New Britain Island in Papua New Guinea. Rabaul town is a community of nearly 100,000 people living inside a large crater which is full of water, since its is open to the ocean and provides an excellent harbor.

In contrast to eruptions from volcanoes in the Pacific Rim of Fire, eruptions on Savai'i, like in Hawai‘i are from small cones and craters, often aligned along cracks or fissures in the ground. The lava flows spew out quietly and with little violent explosive activity. Savai'i flows are typically very thin, usually only two to three meters in thickness and flow very easily out to cover vast areas as they did during the historic periods of eruption.

At the time of the 1905-1911 eruption most buildings in the villages were constructed of timber and burned. The only permanent building in each of these villages was the church. The cement walls of one church remain intact. The lava flowed into the church by way of the main door and filled the church to a depth of about one meter. Today you can just walk upright into the church through the center of the arched doorway. Evidently everything in the church caught fire, including the timber frame roof. Pieces of bent corrugated roof iron can still be clearly seen, now welded into the flow inside the church.

Today on Savai'i each and every person is exposed to the risk of such an event occurring again. Inevitably it will, and hopefully the results of a recently completed SOPAC survey of the volcanic hazards of Savai‘i by volcanologist Paul Taylor will provide the basis for improved disaster management in the light of future activity.

It is perhaps ironic that rocks erupted from basalt volcanoes when they are exposed at the surface of the Earth and weather over time to produce some of the most fertile soils in the world. These in their turn attract agriculture and, of course, people to live on the flanks of such volcanoes.

Here in the Pacific Islands, as learned in the case of the latest eruption of Savai'i, preparedness plans to cope with such disasters must include evacuation strategies and maybe permanent relocation of communities, a problem not easy in Pacific Islands where land ownership can be a contentious issue. Equally important is the total loss of very large acreages of what may be fertile land for agriculture and forestry together with lagoon and reef fishing grounds.

As part of this preparedness, island governments of the region should be encouraged to develop and continue to provide information through public awareness programs and prepare and promote natural hazard maps drawn at the appropriate scale. In order to accomplish this many governments have access to additional resources through membership of SOPAC, which stands ready to assist its member governments with the collection and presentation of this data when requested. Such was the case with the recently completed work on Savai'i.

For more information, contact: Russell Howorth SOPAC Program Manager Tel: (679) 381-377 Fax: (679)370-040 E-mail: russell@sopac.org.fj

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