Sunda Strait harbors Mother Nature's mysteries

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.