The Dieng Plateau is also a volcanic landscape (technically a "complex volcano", an "an extensive assemblage of spatially, temporally, and genetically related major and minor volcanic centers with their associated lava flows and pyroclastic rocks [Francis, 1994]), and the tell-tale features that provide a clue to the tectonic violence just beneath the surface of the Earth are a significant attraction here as well. There are a couple of stratovolcanoes ( including the Sumbing and Sondoro volcanoes)here and a number of craters. Other features include fumaroles, which are volcanic openings in the earth's crust where gas and steam escape, and solfataras, which are fumaroles that emit sulfurous gases (2). All of these features suggest that the Dieng area has been affected by numerous phreatic eruptions. Phreatic eruptions happen when magma rising from below comes into contact with water beneath the surface. This causes the water to quickly turn into steam, which increases the pressure below the ground. When enough pressure builds up there is a violent, explosive eruption that sends steam, ash, rock, and water everywhere. As you can imagine, the Dieng plateau can be a very dangerous place, not just for the phreatic eruptions but also due to the fumaroles. For example, in 1979 149 people were killed when they tried to flee the area. For several days there had been signs of an impending eruptions, so some villagers decided it was a good time to head for the hills (3). Several days later the villagers were found dead on the trail, lined up as though they were walking. Authorities presumed they all suffocated when a cloud of poisonous gas descended upon them. But despite the dangers, the Dieng plateau, because of its cooler temperatures and rich soils, is an important agricultural region. The government has also initiated a geothermal project to generate electricity. We stopped at a hot spring where water and gas bubble up from below. If you've ever wondered what it smells like when the earth farts, you should visit this place. The smell comes from sulfur, one of the principle substances ejected from volcanoes and springs. I've included a video clip of the bubbling pool for your viewing pleasure. Unfortunately the blogging software doesn't come equipped with Smell-O-Vision.
One of the best things about the trip, though, was getting there. During the 3 hours it took to go from Jogja to the plateau we passed through some stunning scenery. Climbing into the mountains you'll pass miles and miles of vegetable farms. The milder climate allows farmers to grow a wide variety of produce, including potatoes. But the striking thing about the agricultural landscape is the density of it; virtually every nook and cranny is planted with some sort of vegetation. Entire hills have been completely given over to terracing. And while this enables increased agricultural production, the environmental consequences are very apparent: slope failures that have resulted in landslides. I've included a series of photos to the right to give you an idea of how this happens. In the first picture (sorry about the blur; I took it from the car) you can see a farmer working on freshly terraced area. Terraces are created by removing all the vegetation and cutting into the mountain to create a level surface for planting. This has two very negative effects: 1) the trees and other vegetation serve as anchors for the soil; their roots help keep the soil in place, and 2) the walls of the terrace increase the slope of that part of the hillside to nearly 90 degrees, which increases "shear stress" and weakens the structure of the slope. In the second picture you can see an entire hill covered with terraces. Nearly all of the original vegetation has been removed and only a few trees remain. In the third picture you can see the unfortunate results of this farming strategy: a landslide. The one in this picture is a relatively small one, but in some cases a significant portion of the hill comes tumbling down. Although the farmers construct rock walls to reinforce some of the terraces, it's usually just a matter of time before a landslide happens in this very rainy environment.
(1) For a short time between 1811 and 1818 the British controlled Java. This was a part of the Napoleonic Wars in Europe. France's Napoleon conquered the Netherlands, and thus took over all the Dutch colonies. France's enemy, England, then invaded Java and after 45 days took control. The English ceded control back to the Dutch at the end of the war.
(2) The name solfatara comes from a crater of the same name near Naples, Italy. Although the volcano is dormant, it still emits sulphurous gas.
(3) Or, in this case, out of the hills...
Francis, P. 1994. Volcanoes: A Planetary Perspective. Oxford University Press, New York, 443pp. Via Oregon State's Volcano World site.
Van Bergen, Manfred, Alain Bernard, Sri Sumarti, Terry Sriwana, and Kastiman Sitorus. 2000. Crater Lakes of Java: Dieng, Kelud, and Ijen. Excursion Guidebook for IAVCEI General Assembly, Bali 2000. Find Here....