Gede Pangrango National Park

Gede Pangrango National Park consists of twin volcanoes: Gede 2,958 m asl, and Pangrango, 3,019 m asl. The mountains slopes are very steep and are cut into by rapidly flowing streams which carve deep valleys and long ridges. Such features are typical of a young and highly erosive landscape. Generally, the area within the National Park is well drained but the few swamps that do occur - Rawa Gayonggong, Rawa Denok and Situgunung - enrich the variety of habitats. What a first glance appears ageless, actually results from the continuing interpay of powerful, dynamic, natural forces: on the hand, the folding of the earth's crust and volcanic activity buliding up the mountains, and, on the other, the destructive forces of the atmosphere - water and wind - cutting into the rocks and transporting away vast quantities of eroded material.

While impressive in their own right, Mts Gede and Pangrango are merely the latest eruption

points on older volcanic complexes. Pangrango is perched on the very top of a huge crater

rim known as Mt Mandalawangi. Over time this parent volcano has been eroded away, as the presence of many dissected river valleys readily testifies. Even so, the outline of its 3.3 km-wide caldera (giant crater) can still be mad out, stretching away southward. The steep slopes of Pangrango, in contrast, are still relatively unweathered, indicative of their more recent origins.

Pangrango evokes aesthetic feelings of what a graceful volcanic cone should like and, reflecting its tranquil appearance, the mountain is classed as extinct. On the other hand, Gede is a very dangerous volcano. Currently deceptively quiet, viewed over time Mt Gede is one of the most active volcanoes on Java. The Directorate of Volcanology is certainly not complacent about the risk it poses, and maintains a monitoring station near the Puncak Pass. The new Gede summit also sits on an older volcanic complex. The original Gede caldera measured 1.8 km in diameter. A newer, slightly smaller crater rim of 1km diamete, has built up on the floor of the old caldera: the old and new rims forming two overlapping circles.

Geology - How the Mountains Formed

There are about 40 major volcanoes scattered along the length of Java, they form part of the Pacific Rim of Fire: over 30 may still active but 17 are officially listed as such. These volcanoes have been formed during the Quarternary period, around one million years ago to the present time. Pangrango and Gede are thus comparatively new mountains.

"Sleeping" volcanoes that emit steam and gas, such as Gede, are described as being in a "normal active state". Gede's well-defined if irregular crater area is devoid of thick vegetation: vents, termed solfataras, release poisonous, sulphur-rich gases which inhibit plant growth. In the past, volcanologists mapping Gede carried up like chickens to make sure that the air was safe to breathe. People venturing close to sulphurous-steam vents can run into serious trouble, particularly when the wind changes direction, finding themselves enveloped in a choking cloud of sulphuric acid, sulphur dioxide, hydrogen sulphide and carbon monoxide. Not for nothing are the areas around such vents called death valleys.

The modern theory of plate tectonics has done much to explain the natural processes that result in volcanic eruptions such as those of Gede-Pangrango. The earth's surface is like that of a cracked egg. Each "shell" fragment is called a plate. Java lies right on the edge of the Eurasian plate, and running all along Sumatra and Java's south coast is a "crack" or plate boundary; the boundary has formed where the Eurasian continental plate "bumps into" the oceanic plate carrying Australia. Oceanic plates are made of heavier rocks than those continental in nature. Hence, where the two plates meet the margin of the Australian oceanic plate sinks (subducts) beneath the lighter Eurasian continental plate. The subduction zone is the principal cause of both earthquakes and eruptions on Java.

As the edge of the oceanic plate descends, it drags down surface debris including fragments from the edge of the overlying continental plate. As all this material sinks below the Earth's crust, it becomes very hot and melts. This now "molten rock", derived from the Earth's crust, is less dense than surrounding material. It consequently rises upwards and melts a row of holes, causing a series of volcanic "hot spots", one of which is Gede-Pangrango.