Since 1991 four deadly landslides or floods have struck the region and claimed thousands of lives.

In the latest disaster Friday one side of Mount Can-abag crashed onto the southern village of Guinsaugon, a settlement of about 3000 people.

The government's Mines and Geosciences Bureau launched a geo-hazard mapping project on southern Leyte following a series of landslides in the adjacent tiny island of Panaon that claimed about 200 lives in December 2003.

Their location on the edge of the highly unstable undersea Philippine Trench means the bedrock of southern Leyte and the northeast coast of the major southern island of Mindanao are "badly broken or fragmented" and are "prone to weathering and erosion," the study found.

When continuous rain falls, the water seeps into and saturates the rock fractures, creating a loose and unstable combination, experts say.

Leyte suffered its worst ever disaster in November 1991 when flash floods and landslides killed about 5000 people in Ormoc, its number-two city.

A landslide killed about 20 people earlier in the week in Sogod town, to the west of Guinsaugon.

Quake trigger

"The area could have really been ready for a landslide because of the amount of rainfall and if there was a minor earthquake, it might have hastened it"

Rene Solidum,
Philippine government seismology office

A mild 2.6-magnitude earthquake that struck nine minutes before the Guinsaugon landslide may have helped trigger off the wall of mud that crashed down on the village, said Rene Solidum, head of the government's seismology office.

"The area could have really been ready for a landslide because of the amount of rainfall and if there was a minor earthquake, it might have hastened it," Solidum said.

Leyte, which has a mountainous interior, and nearby Samar island are the gateways for the 19 typhoons and storms that on average batter the Southeast Asian archipelago every year.

The typhoon season is still some months away but rain falls on Leyte all year round.

The government weather office said 500 millimeters of rain had fallen on Leyte since February 1, nearly five times the normal amount, due to the weather phenomenon in the Pacific Ocean known as La Nina.

The environment and natural resources department said the natural forest cover of southern Leyte, which would have helped prevent erosion, has been replaced to a large extent by coconut plantations since the 1920s.

Pressure on the land

The encroachment of people in vulnerable upland areas has also been blamed for the frequent landslides in the Philippines.

A series of landslides on the mountainous east coast of the main island of Luzon in November 2004 claimed more than 1000 lives.

Out of the national population of 85 million, "around 24 million people are estimated to be living in the uplands and, as such, puts tremendous pressure in our forests," environment and natural resources assistant secretary Analiza Teh said late last year.

The upland population would double in 30 years at present trends, she added.