Sunda Strait harbors Mother Nature's mysteries

Today marks the 112th year since the deadly eruption of Mt. Krakatau. It is one of the most violent explosions known to man and brought about global environmental changes in the 19th century, including a 0.5 degree centigrade drop in temperature until 1888. The bang reverberated as far as Saigon, now Ho Chi Minh City, and Perth. MMI Ahyani, a final year student of the Geophysics Department, Bandung Institute of Technology, reveals what happened the day the famed volcano erupted, explores what the Sunda Strait hides below the surface and investigates how the volcano is monitored.

BANDUNG (JP): "To develop tourism in West Java, or on Sumatra's east side, it would be impossible to leave out the name Krakatau. The history of these regions was greatly influenced by Mount Krakatau," said Dr. Axel Ridder, a German socio- anthropologist who managed a hotel on Carita Beach in West Java.

Dr. Ridder based his opinion on studies conducted in the 1970s about the region's development prospects in relation to its social history. It turned out that Dr. Ridder's analysis was near the truth.

A rift developed between West Java and Lampung because both claimed the famous volcano. Geographically, the cluster of Krakatau islands is located in the administrative zone of Lampung. But, it is better connected to Serang, Pandeglang, Labuhan, Anyer and Merak in West Java.

Krakatau can be reached by a four-hour boat trip from Carita Beach in Java or by a six-hour voyage from Kalianda Beach in Sumatra to Sebesi Island and then on to the Krakatau islands.

The Aug. 27, 1883, eruption of Krakatau had many implications. A city known as Caringin Site completely disappeared and a study team from Harvard found that the destruction of certain species of what? animals? birds? trees? appears to have created new species.

The Sunda Strait's geodynamic attraction is its tectonic activities. The complexity of a tectonic situation can be explained by means of the plate tectonics concept, which indicates that a transitory region of two plate subductions can be found. The Indo-Australia plate is moving to the north, where it plunges under the Asia plate.

The Sunda Strait between Java and Sumatra is widening towards the west, 25 km between Anyer in West Java and Bakauheni in Lampung, 100 km between Ujung Kulon (West Java) and the most southern part of Semangko Bay (Lampung). Mount Krakatau is located smack in the center.

Based on the topography of its bottom, the Sunda Strait consists of two regions divided by Mount Krakatau. To the east of Krakatau, the ocean is 120 meters deep, while in the west it is 500 meters.

To monitor Krakatau, a telemetric quake measuring observation system has been fixed around the very active volcano. Aside from research conducted by the Directorate of Volcanology, scientists from the National Institute of Sciences and the Agency for the Application and Assessment of Technology and universities also study Krakatau.

Another team of the Gadjah Mada University led by Kirbani Sri Brotopuspito and Waluyo from Gajah Mada's School of Mathematics and Physics has established an observation station on Carita Beach. Sensory equipment has been fixed on Anak Rakata and Carita and in Kalianda, Lampung. More will be buried on Panaitan Island, Ujung Kulon.

"Data from each station will be correlated with information from other stations. This is possible since on-the-spot data is available," he said.

Anak Rakata re-emerged in 1927 and now reaches 250 meters above sea level. The eruption points, named after the years they blew in 1979, 1988 and 1992, seem to continuously move. Observations are not restricted to these three cauldrons, eruption points buried under lava are also studied.

Igan Sutawidjaya, the chief of the West Java and Sumatra Volcano Observation Section, estimates that Anak Rakata has erupted 75 times. Blowups occur routinely once every eight years.

The eruption between November 1992 and April 1994, yielded 13 million cubic meters of material.

"This is the reason behind the speedy change of Anak Rakata's topography. It would be extremely dangerous for the inexperienced to land on Anak Rakata. They don't know where or in which direction the eruption point are found," he said.

This ignorance killed an American tourist and wounded his five companions when they tried to land on Anak Rakata.

"His head was struck by a red hot burning piece of lava. These red glowing volcanic bombs are extremely dangerous," warned Igan.

It is suggested that tourists watch Anak Rakata's activities from Pulau Sertung, located a safe distance from the flying lava.

If the team of the Directorate of Volcanology stresses research and observation for disaster mitigation, college and institution researchers are conducting complementary research to reveal the geophysical innards of the Earth, including studies on seismicity, gravity and geoelectricity.

It is hoped that a model of the Krakatau eruption can be reconstructed from the results.

"This model will, of course, benefit forecasting eruptions to mitigate the dangers. Besides, the equipment on location will be tested," said Kirbani Sri Brotopuspito, who is also chairman of the physics department at Gajah Mada's School of Mathematics and Physics.

The equipment must be tested because the environment, with sudden differences in temperature, can be very corrosive.

It is hoped that the natural laboratory of Krakatau will divulge data to help humans interpret the happenings in the inner most depths of the Earth.