Written by: Professor I.W.B Thornton/Zoology Department/La Trobe University, Melbourne University
A GUIDE TO KRAKATAU
The Director General of Tourism is encouraging all those associated with the tourist industry, to make known worldwide, Indonesia’s potential for tourism and scientific study. One of Indonesia’s treasure is, of course, the Ujung Kulon National Park which extends across the Sunda Strait to include the active “Krakatau” volcano.
No visit to Indonesia can be complete without a visit to Krakatau, “ the volcano shook the world”. A television film has been made about the fatal eruption, identifying environmental repercussion to date. It has shown worldwide since 1983.
Your visit will be be adventure tourism, starting with a 2 hour boat trip to Krakatau departing from Carita Beach. Professor Thornton has produced a recommended itinerary for your visit which will minimize any risks involved with your adventure.
We ask your cooperation however in preserving this unique natural monument to nature. Continuing study and research into this naturally developing ecosystem demands the utmost care by tourists not to drop litter or destroy developing life. Future generation will wish to travel to Krakatau to enjoy the awe inspiring silence and moonlike landscape of Anak Krakatau during its “sleeping” period.
We hope you have a good journey.
To anyone interested in natural processes, Krakatau is one of the most fascinating areas in the world. The cataclysmic eruption eruption of 1883 captures the imagination, and spectacular volcanic activity continues to the present. To those interested in biology and the way islands are colonized by plants and animals. – not only the islands from which life was eradicated by the 1883 eruption, but also the new island of Anak Krakatau – the area holds a unique attraction.
The Krakatau islands are part of the Ujung Kulon National Park. This park also includes the famous Ujung Kulon wildnerness area on the westernmost peninsula of Java – a reserve for the only remaining population of the Javan Rhinoceros.
The three outer islands of the present Krakatau group (Rakata, Sertung and Panjang) are thought to be the remnants of the one previous, huge volcanic island. Called “Ancient Krakatau”, it was some 11 km in diameter and 2 km high. According to records in the Javanese Book of Kings it exploded and collapsed, perhaps in prehistoric times but posiibly as recently as 416 AD. Three islands remained on the rim of its submerged, 7 km diameter, central caldera (collapsed crater). The southernmost of these, Rakata grew by volcanic activity until it was 830 m high and 5 km in diameter. Two smaller volcanic islands, Danan 450 m and Perbuatan 120 m, then developed in line and to its north, within the ancient caldera. The three islands later joined up into one, Krakatau. This was about 9 km long and 5 km wide. There are records of seven eruption of Krakatau between 9th and 16th centuries. By the 19th century it was regarded as dormant.
The 1883 explosive eruption
Volcanic activity recommenced in May, 1883 and continued into August, the first eruptions appearing on the northern, perbuatan volcano. The number of active vents increased on both the northern volcanoes. On the 26th and 27th August a series of cataclysmic explosions occurred which were heard as far as South Australia and Ceylon. They generated tsunami that were registered even in the English Channel, and which in the Sunda Strait area were devastating, killing more than 36,000 people. The total volume of material ejected by the eruption is estimated at some 18-21 cubic kilometers, with an ash cloud circling the earth several times, causing “blue suns” and “orange moon” in Europe and North America. The amount of the sun’s energy reaching the earth was reduced, in the year or two that followed, annual average temperatures in the northern hemisphere were lower than usual.
In the aftermath of the explosions only about a third of Krakatau remained. The northern two-thirds, including the volcanoes Perbuatan and Danan and the northern half of the Rakata volcano, were gone. In their place was collapsed crater (caldera) 200 m beneath the sea, covering an area of about 28 square km. the remaining, southern part of Rakata was left as approximate half-cone with an almost perpendicular cliff from the summit (813 m) to the sea, providing a natural, geological section through the volcano. The other two islands, Sertung and Panjang were enlarge considerably (Sertung doubled in size) by the glowing ash and pumice which smothered them to a depth of 30 metres. On Rakata, the south and west coasts were extended almost a kilometer seawards and ash layer reached a thickness of 60 m in some areas, although probably much shallower on the steeper slopes. Weeks after the explosion, rain water turned into steam as it trickled into crevices and even a month later the surface was too hot for bare feet. It is believed that all life, plant and animal was destroyed on the islands. Yet the three islands are now covered forest, and over 200 species of higher plants and 36 species of land birds have been found on Rakata in 1980s.
THE BIRTH OF ANAK KRAKATAU
40 years after the main explosion, in 1927, volcanic activity was seen in the sea covering the old caldera, between the sites of the two northmost former volcanoes of Krakatau, where the greatest activity had occurred at the time of the cataclysmic. A series of eruptions 185 m below the surface of the sea resulted in the emergence of three new islands, one after the other. They were all soon destroyed by surf. A fourth emerged from the sea on August 12th 1930. It remained above water, and was aptly named Anak Krakatau (Child of Krakatau). It grew by accumulation of ash, and suffered a devastating eruption in 1952, and another very destructive one in 1972. The northeast coast, north foreland, and east foreland are now vegetated; the succession of vegetation is still at an early stage, Casuarina equisetifolia (Cemara) being the dominant tree.
The journey to the islands takes about 2 hour on a good day by speedboat, and the best time of the year to make the trip is between May and October. During monsoon season (November to April) the time taken may be very much longer and the journey uncomfortable, although there may be storms in any month of the year, at this time they are frequent and the journey can be dangerous.
Keep your eyes open, and you may see a frigate bird soaring high overhead, flicking its scissor-like tail as it changes direction with hardly a flap of its wing. You will almost certainly spot flying fish making their long low glides above the sea’s surface. Some of them “fly” for ten metres and are airborne for several seconds. Approaching the Archipelago, group of dolphins often come to greet the boat and play alongside it or in front of the prow. You may also be lucky enough to see a White-Bellied Sea Eagle as you approach the islands. It has a slow, gliding flight with the wings held in a shallow “v” as it soars, searching for sea-snakes, fish and crabs swimming near the surface. As you near the archipelago, the triangular silhouette of Rakata looms ahead. The island takes its name from Krakatau’s largest volcano, of which it is the remaining half. Cloud often covers the peak down to about 550 m, and above this height the forest begins to take on a different character. Mosses festoon the branches of trees, which are stunted at the peak. To the south (near the left side of the island as you approach) is a bay in which a settler named Handl lived with his family for a few years from about 1915. There have been no other permanent inhabitants on the island since 1883, although fishingboats visit the archipelago reguraly, the water within the island group often being calmer than the open sea.
Panjang, formerly called Lang Island, and sometimes known as Rakata Kecil was never part of Krakatau, but was once a part of Krakatau’s huge predecessor, “Ancient Krakatau”. Like Rakata and Sertung, it was covered in tens of metres of hot ash in August 1883, and this has been eroded over the past century into v – shaped gulleys separated by sharp ridges. Like the other two islands, it is now covered in forest. Some of the valleys are now ‘hanging’, because the ash cliff has been cut back by the action of the sea so that the valley floor now open at a considerable height above the shore. To your right, on the south western point at Panjang, the lava rocks of “ Ancient Krakatau can be seen near the base cliff.
Now to your left as you round its northern point, Rakata’s huge vertical cliff tower above you. Again, towards its base, the layers of Ancient Krakatau’s lava rocks may be seen, with ash layers between them, evidence of successive eruptions centuries ago. Casuarinas (cemara) cling to the cliff. They cannot tolerate shade, and on most other parts of the island they have , been overgrown and thus eliminated by other forest trees. Landslides are frequent on this cliff, and the prominent groove down the cliff face is not the former vent of the volcano, but a landslide Channel from close to the summit, pile of rubble, the result of landslide, can be seen at the base of the cliff. At the far end of the cliff are the black rocks of Zwarte Hoek, where there is a small beach.
As the boat moves under the cliff, remember that you are traveling over the submerged caldera of Krakatau. The cliff continues almost vertically under the water below you to a depth of about 200 metres. To your right, if the is calm you may be able to see Bootsmanrots behind you. These rocks often with seabirds usually terns roosting on them are a favourite spot for shark fishermen, and shark’s fin can occasionally be seen cutting the water over the caldera. The rocks are Krakatau’s caldera rim which projects above the water at this point. Apart from Rakata itself, they are only other piece of Krakatau visible above water today. Of course, no one could have been in this place before August 1883. Your boat is travelling along a line which at the time would have been covered by thousands of tons of the island Krakatau, which extended far to the north beyond the island Anak Krakatau to you right.
Moving past Zwarte Hoek and heading towards Sertung, you will notice, beyond the point to your left, a long sandy beach where the green turtle (Chelone mydas) nests, and just out to the sea two large isolated ‘stacks’. One of which has been perforated by the sea. These light-coloured cliff stacks, and cliff along turtle beach are composed of ash deposited in the 1883 eruption of Krakatau, and give you an idea of the depth of ash that covered the island at the time. The stacks have been able to persist because they are on a basement of lava which has prevented the sea washing them away.
Ahead is Sertung, the third member of the trio of islands that remnants of the huge Ancient Krakatau volcano. Sertung was enlarged by Krakatau’s 1883 eruption to more than twice its size. And is now virtually composed of ash from that eruption.
To your right is the presently active volcanic island, Anak Krakatau “Child of Krakatau”. This is an apt name for the island emerged from the sea 1930 from Krakatau’s caldera, roughly in line with its three former volcanic craters and between the sites of the two northern ones. The lava field you see is composed of a number of different flow, the most recent one (1980) being the darkest. Lava di not appear until some time in the 1960s, and this important in protecting the rest of the island from erosion by the southwestern current. Before the 1960s Anak Krakatau had emitted ash only, but such a rate and frequently enough for it to grow, in spite of the marine erosion.
As you leave Sertung and move back towards the northern foreland of Anak Krakatau, with Rakata’s cliff looming up beyond in the middle distance, you are travelling over the northern and of the submerged remains of Krakatau itself. Anak Krakatau is largely barren, being made up of ash fields or lava, but on the northern foreland you can see a number of cemara trees and an extensive grassland of “Alang-alang” and wild sugarcane. This grassland was a very early stage (before cemara) in the plant colonization of the other islands, and the process is being repeated here on Anak Krakatau. Moving around to Anak Krakatau’s landing beach on the eastern foreland, you see more cemara woodland – this foreland is at a later stage of plant succession than the northern one.
Going ashore, you will notice other trees and saplings here and there among the cemara and wild sugarcane – the forest is beginning to change to mixed secondary forest. Two species of fig trees are present, they were first seen fruiting in 1985. There are three species of bats on the island (of a total of 11 on the archipelago). Two kinds of dog-faced fruit bat and a rousette. All three are fig eaters. Also two species of fruit-eating pigeons (pink-necked pigeon and cuckoo dove) as well as the yellow-vented bulbul and the striking, yellow and black, black-naped oriole now live on the island. These birds and bats spread figs by dropping or excreting their seeds, and probably were responsible for bringing the fig species to the Krakatau from the other islands. They will probably bring more fig species to Anak Krakatau, and the change towards mixed forest is likely to accelerate in the next few years.
You may see the bright yellow breast of the tiny olive-backed dunbird as it seeks nectar and insects, clicking as it goes, and perhaps, its nest hanging from a cemara branch. Keep alookout also for another very small, yellow-breasted bird, the flyeater, flying from branch to branch in the cemara, or small flock of a larger bird, the white-breasted wood – swallow, perhaps six or seven of them perching together along a high cemara branch. Almost certainly you will see and hear the collared kingfisher, greeny-blue with a white collar. This is one of the most successful colonists on the islands. It makes nest holes in the large spherical termite nests that you see here and there in the cemara tress, and noisily and aggressively defends its nes-site from other intruding birds, such as the wood – swallow.
Only about 14 hectares of Anak Krakatau of Anak Krakatau are vegetated, and you will get and an idea what a small part of the island this is if you climb to the marker on the rim of the the outer ash-cone, a strenuous walk, to be attempted at mid-day only by the fit. Yet this small area of woodland supports about 22 of the 36 species of land birds (not counting migrants) now known on the island. So of the 36 land bird species that have colonisted the islands from Java and Sumatra in the hundred years or so since 1883, 22 of them have managed to established themselves on Anak Krakatau’s eastern foreland in the past 30 years or so Anak Krakatau’s 1952 eruption destroyed all its vegetation. Three of the 9 species of reptiles on the islands have also become established on Anak Krakatau. The large, very common monitor (varanus salvator) a relative of the famous komodo dragon, is a good swimmer and feeds on crabs and turtle eggs. The common checkchak gecko (Hemidactylus frenatus) and the flying (really gliding) paradise tree snake (chrysopelea paradise) have also colonized Anak Krakatau, the last probably by means of floating vegetation or logs, which you will have already noticed are common on the beaches. Only one of the 19 species of land snails on the islands has yet reached Anak Krakatau – it was first noticed on Rakata in 1933. There are rats on the archipelago – the house rat (rattus rattus) on Rakata, and the country rat (R. tiomanicus) on Panjang and Sertung. Only one individual (a house rat) has ever been found on Anak Krakatau in 1985.
The tokay (geckko gecko), which is a gecko-eater, and black eagle, python and fasle vampire bat are present on the other islands but have not yet been found Anak Krakatau. Probably they have not colonized it because they do not yet have a sufficiently reliable food supply there. Also, several forest birds, such as the brown-capped woodpecker and orange-bellied flowerpecker, which require large trees, have not yet colonized this island although they are present on the others.
For the study of change, both physical and ecological change, the Krakataus are a natural laboratory – in fact two laboratories in one. Changes both in the archipelago since 1883, and on Anak Krakatau since 1930 are being studied. So that this work is not made more difficult by artificial changes brought about by humans, please keep to trails, do not wander about the archipelago without a guide, and make sure that you neither bring to, nor take from the island any living things (seeds, fruit, insect, etc). Please take your refuse back with you, so that the other visitor may enjoy the natural beauty and ponder on the fascinating history of this unique group of islands.