Krakatau – Part 2

Dr G Trevor Watts

In the fisrt part of this article (Kratatau – Part 1), I started to describe the geology of this famous volcano and also my visit to it. I now continue and you find me on fresh scoria and sulphurous steaming rock, standing on the rim of Anak Krakatau. There is a drop – it is steep, but not vertical – down into the depths. The crater is perhaps 100m deep, with reddish slopes, patched with areas of sulphur (Fig. 1). At the bottom, there is a black pit, about 20m deep.

One boulder, the size of a double-decker bus, rests precariously on its edge. Nothing appears to be emanating from the abyss, but it has an active, ominous feel about it. The black hole seems to shimmer from time to time, as if with radiated heat. To our right and directly opposite, the slopes are intermittently shrouded with fumarolic vapour.

Despite my fervent prayers and beseechings, and a couple of large boulders rolled into the crater, Anak Krakatau didn’t erupt – not even the little burp that I would have been content with. Doni assured me that it was just as well, as the eruptions usually deposit large, glowing cinders all over the area where we were standing. He insisted that this really wasn’t a place where I would want to be during an eruption of any size, even the little one I craved.

Saving his strength and nursing a sprained ankle, my guide decided that I was old enough to be allowed to wander around on my own, wherever I wanted. However, he asked me not to do anything too silly, as he would have to explain to my wife and innumerable officials concerned with tourism and vulcanology what had happened.

So I wandered off to the north-east, anti-clockwise along the crater rim and headed towards the highest point on the island (Fig. 2).

It is a breath-taking experience. On the right, there is a long, convex slope down to the sea, scattered with lava bombs and emitting wisps of fumes. To the left, the land drops steeply into the crater and, all around the faint trail, there are areas of fumaroles and sulphur crystals (Fig. 3).

The walking was easy and the views spectacular in every direction. I could see the nearby island remnants of the former volcano and fresh-looking lava flows down to the sea (Fig. 4).

There were shrouds of steam and fumes, and wide areas of a white crystalline crust, as well as brilliant yellow sulphur patches and hissing vents (Fig. 5).

From the highest point, you can look directly down into the most active area of fumaroles within the crater (Fig. 6).

Beyond that point, approximately opposite to where I started, the rim is shattered into a section of tumbled rocks that drops precipitously. There is only a very narrow and broken edge that might or might not have been negotiable. From above, it looked very unstable. I decided not to risk it, and started back to where I had left Doni resting.

After a chat with my very laid-back guide, we decided that there was no hurry to return to the camp, so I carried on around the rim. I went clockwise this time, passing over the lowest sections where the rim had collapsed inwards, following the most recent eruptions of lava. Soon, I reached the steep part on the opposite side where I had previously baulked at the prospect of the descent.

However, from this lower perspective, the ascent looked easier than the descent had done. It was still narrow and shattered, with a precipitous sulphur slope into the crater on the right and an equally precipitous slope to the left, a thousand feet or so down to the 2001 lava flow and the sea but, nevertheless, still easier going up than down! After a ten-minute scramble, I was at the top of this steep and rocky section (Fig. 8).

From there I could see a ledge cutting across the inner wall of the crater about a third of the way down the steep face. It didn’t look too risky, so I scrambled down inside the crater. Cutting across loose cinders and rock, as well as more sulphur deposits and hissing steam vents, I reached the ledge at a point where it broadened out to form a shoulder of rock about 40 metres below the rim. From the lowest point I got a real feeling of being inside the crater, with the steep walls rising all around me, the sulphur fumes drifting by spasmodically, and periodic blasts of very hot air circling around (Fig. 9).

Although the view upwards was awesome in all directions, the view into the depths wasn’t as good as it was from the rim, because the slope was slightly convex, and the deepest part of the inner pit was hidden beyond the curving slope. This low section of the rock shelf was almost blocked by a scree of loose rocks that had fallen down the inner face. It looked as though a descent any deeper into the crater would have been pushing my luck a bit too much, so I offered up a few more heart-felt prayers for a token eruption. However, these again went unanswered, so I collected some small samples of cindery lava and climbed back up to the spot where I had started the descent, rather than crossing the loose debris on the shoulder and ascending on the opposite side (Fig. 10).

Once I had returned to the rim, I continued on round the edge of the crater, again passing the highest point, and stopping to photograph one of the patches of sulphur deposits that was 20 or 30m across. In these areas, all the loose rocks that had been hurled out of the crater were glued together by swathes of sulphur that formed a crust over and between them.

The sulphurous smell wasn’t as strong as I expected: the main sensation was the pervasive heat that was coming from the ground all around me. In some places, the rocks were too hot to touch and, when my foot went through the fragile crust of layered sulphur deposits at one point (Fig. 11), the heat was unbelievable. As Doni had said earlier, the volcano was exhaling, and this was a whiff of its hot breath. The heat from the ground was supplemented by the heat that was rising from the crater: this section of the rim, although high, was the downwind part of the walk.

The breeze, which had been so welcome during the climb, was now swirling around inside the crater and was rising up from the depths. It seemed to be funnelling towards this small section of the edge, which it hit like the blast from a gigantic oven door being opened. It was absolutely stifling, worse than when I had been inside the crater. This was no place to linger for more than a few moments to take a photograph or have a quick swallow of warm water.

I collected a few more pieces of multi-coloured mineral crust and also some bright sulphur crystals and cinders, then went back to where my guide was waiting (Fig. 13). A cold drink was very welcome and, as I drank it, I offered the volcano one more chance to do the right thing and erupt, just a little bit. Then it was time to return to the beach.

Again, the trekking poles proved their worth on the treacherously loose, downward slopes. Over some sections of the descent, it was possible to ‘scree-run’ in an ice-skating style. However it’s not something I’m keen on, as a blow from a single rock can break a leg, or glass-sharp, volcanic scree can fly into your face. Even so, the return took less than an hour. It was after 4pm by then and the heat had gone from the sun, especially as the main slope was in shade. Lower down, the breeze vanished as we dropped into the lee of the rounded slope and the tropical heat descended on us for the rest of the journey.

Once on the beach and with feet blackened by dust, it was time for a dip in the sea. It wasn’t safe to venture too deep, as there was a strong rip current and this was clear from the change in wave pattern, about 30m out from the shore. In fact, it was sometimes possible to hear the current’s ‘zipping’ noise as it clashed with the calmer, in-shore waters. The evening’s entertainment consisted of the university contingent trying to put up hammocks between the trees, and eventually settling for tarpaulins on the sand. Supper was garlic rice, with freshly baked fish from our unscheduled stop in the Sunda Strait, as I mentioned in the first part of this article.

One of life’s great pleasures was introduced to me that evening – cold Bintang – the local beer. Very fine it is too, especially when it’s been kept in an ice-filled cooler on a hot and dusty day. A long evening chat was a more sober but no less pleasant affair for my guide and the boat’s crew. As the evening drew out and we chatted round a paraffin lamp, the fishing boats along the beach began to light up and set out to sea for the night’s fishing. They took up station perhaps a kilometre offshore, forming a line of lights about a 100m apart. They mainly catch squid and a local variety of mackerel, but are happy to take anything that arrives in their nets in the darkness.

It was obvious when it was bedtime – the beer ran out. As the air was still warm and humid, I decided to spurn my tent and sleep on a plastic sheet and blanket, with an unzipped sleeping bag across me. I was warned of large lizards, about a metre long, being loose on the island (Fig. 14). Apparently, they venture onto the beach at night, scavenging for washed-up food, and they are rumoured to be curious about anything they find. The stars were incredibly bright and the Milky Way so clear. It really was like a great, pale-silver banner across the black sky.

Lizards did not disturb us during the night, although we did see track-marks further along the beach in the morning. As I lay in my bed, the sound of crashing waves, a few metres away, was alternately soothing and disturbing when the wind picked up towards morning. To my surprise and delight, there was a large, black, swallow-tailed butterfly on my sleeping bag when I finally awoke, but follow it as I might, I couldn’t get a decent photo as it fluttered along the beach on the fringe of the forest.

The sea was very choppy between the islands – across to Panjang, there were waves two metres high. They weren’t bad on the beach, as they were coming from the south and we were in a protected lee. However, the weather forecast told of increasing winds and rough seas, and we were due to go to Panjang for views back to Anak Krakatau and an hour or so of snorkelling. After a coffee and having de-rigged the tent we decided that the waves and wind really were picking up and it would be safer getting out of the inter-island channel before things got too bad and we were marooned on the island (Fig. 15). So, the snorkelling was abandoned in favour of a quick dash back to Anjer.

It was not to be. Leaving the beach was no problem in the shelter of the southern point, but as soon as the boat got into the main channel between the islands, the waves hit us. We were battered and tossed about from all directions, and were drenched in salt spray, and green water was coming over the side and stern.

It was rather nerve-wracking for the first half hour, as we tried to keep clear of the cliffs of the outer islands while not being too exposed to the main run of waves that were forcing their way between the islands. Then, we were in the open sea of the Strait and our troubles really began. The wind was force six and the waves more than two metres high, coming at us from the starboard bow. It was purgatory, crashing into the fronts of waves, then lurching down the other sides, endlessly repeated, until… one engine faltered… and then the other.

Twenty minutes of searching and discussion from the crew failed to produce any fuel from the ether. We had run out of petrol, in the middle of the Sunda Strait, in a near gale force wind and there was no vessel or land in sight. This was the downside of the accidental diversion we had taken on the way out – too much fuel used then and not enough left now. Doni took it very philosophically and went to bed. I tried to keep fixated on the horizon, which seemed to wallow in all directions now the boat was without power and unable to keep its nose into the waves.

The crew dropped a sheet anchor overboard in an effort to improve the vessel’s stability and then cast out with fishing lines. Their unhappiness stemmed from their lack of cigarettes more than the lack of fuel. Fortunately, the heavy swell was dying down to a slow, gentle lurch, but an hour’s wallowing and rolling didn’t help a lot. I was developing a deep feeling of queasiness by the time a tiny boat appeared on the horizon. Hurtling across the wave tops, it was a speedboat no bigger than a rowing boat, and it carried a couple of barrels of petrol and a bottle of two-stroke mixture. The crew had been busy on their cell phones and had managed to get through to Anjer. They cheered up immensely as their friends drew closer and quickly reeled in the fishing lines, having had no luck.

Two fifty-litre drums of petrol, the two-stroke mix and a packet of cigarettes were passed between boats with consummate skill. As the tiny boat pulled away, the crew urgently called it back – they needed matches for the cigarettes. Five minutes later, the fuel lines were dropped into one of the open drums, one crewmember sucked the petrol through and they all calmly lit their cigarettes. It became a race back to Anjer between our saviours and us.

This was headlong, jarring stuff, and we held onto anything that was fixed. However, the smaller rescue boat couldn’t keep up the same speed going into the waves, as it had done on its approach. Soon, we saw the Anjer lighthouse looming up out of the midday haze. By then, the waves were smaller, so the sharp turn into the harbour entrance wasn’t too hairy and we were very soon moored alongside the jetty with our gear being unloaded. Two minutes later, the smaller boat pulled alongside us, with everyone laughing and joking.

The trip of a lifetime? It was certainly memorable. Maybe Krakatau hasn’t got the awesome pit of Telica, the fumaroles of Kawah Ijen or the night displays of Arenal, but it does have one thing the others don’t: pedigree. It has to be the most famous volcano on the planet. It staged the first ‘World Event’, because the 1883 eruption was at the time of the early telegraph connections around the world. And this was the first occasion of worldwide interest, so news of it was flashed around the globe virtually as it happened. The volcano’s fame was great then, especially as it was credited with slightly raised tides the world over and reddened sunsets for two years. And its fame lives on, in international folklore (Fig. 16).

The day after our trip, we visited the seismology monitoring station south of Anjer. The revolving drums on which seismic tremors are recorded showed clear records of the recent earthquakes off the Sumatran coast (Fig. 17). But there was no indication of any of the eruptions on Krakatau reported by the university research party when they said they had seen the sky lit up, and the sound of explosions. However, a revival of eruptions was expected, as it is believed that Krakatau is linked to the same Sumatran subduction zone that had caused the earthquakes.

On the walls of the seismological station, there were several framed pictures of the volcano erupting in 2001. Unfortunately, the dust and coffee splashes on the glass didn’t make it easy to look at them, but the faded pictures conveyed some idea of the considerable size of the eruption.

The expected eruptions actually began a few weeks later on 22 October 2007 (Fig. 19). I received emails and photographs from Doni, telling of new activity on Anak Krakatau. We had been there less than a month before. The area of fumaroles on the flank where we had walked on the final stretch up to the crater had suddenly erupted, forming a new crater below the main one. The volcano hadn’t stopped breathing – in fact, it was coughing.

Since then, the eruptions have been getting stronger in cycles of greater and lesser intensity. They began as small explosive bursts that scattered showers of rock across the slopes. Columns of ash were reaching 800m into the air throughout December 2007 and there were frequent fountains of rock and cinder. This activity cleared a large area of the southern flank of Anak Krakatau, and created an explosion hole, into which a circular section of the volcano flank collapsed. This completely obliterated the area where our path rose to the main crater rim.

By the end of December 2007, the rock fountains were no longer composed of mainly the existing country rock being excavated into the atmosphere: they then comprised Strombolian fire fountains of incandescent spatter bombs, from deeper within the volcano. The ash columns were then reaching 3,000m in height, lava flows were visible from the surrounding islands and volcanic debris was being deposited over all of Anak Krakatau. There was an ‘orange’ alert level of three (with four being the highest level of danger) and a two-mile exclusion zone around Anak Krakatau. The beach sands were heating up, and camping was out of the question, as was the fishing by the locals.

This situation has continued through 2008. Anak Krakatau continues to erupt spasmodically. In mid March there was a significant increase in eruptive activity which peaked with around 80 shallow earthquakes in the week to 16 March. Glowing rocks and incandescent plumes of gas were reaching up to 3.3 km into the atmosphere, often accompanied by deafening explosive sounds. At times, the whole of the south and eastern slopes were ablaze with falling incandescent cinders and lava bombs.

Spectacular pictures of these can be seen on the Internet, including on the sites run by ‘Volcano Discovery’, the USGS and the Smithsonian Institute. Now, in the middle of June 2008, reports indicate that the eruptions have again renewed their strength, with frequent Strombolian eruptions sending ash and cinders a kilometre high. These explosive fountains of blazing rock are sometimes so dense that the whole south-east of the island again appears to be on fire, with lava flows reaching the sea. However, it seems probable that these ‘lava flows’ are not solid flows, but a coalescence of tumbling lava bombs and fiery blocks.

The company that I went with, Volcano Discovery, has organised recent trips to view the eruptions. These involve several nights’ camping on the nearby islands, as the exclusion zone and high alert level are still being enforced. The Indonesian authorities seem to be monitoring the situation closely, and they adjust the level of alert and the extent of the exclusion zone regularly. Volcano Discovery is proposing another visit for early July, camping on Sertung. I expect there will be more visits later in the year by this company, and probably by other companies as well.

Further reading

For up-to-date information on the Internet about eruptions and possible visits, try:

• Volcano Discovery (http://www.volcanodiscovery.com/).
• Volcano News (http://www.volcanolive.com/volcanolive.html).
• Global Volcanism Program (http://www.volcano.si.edu/world/volcano
• KRAKMON Online, which has links to the three seismic stations on Anak Krakatau, as well as one on Sertung, and a digital camera.
• What on Earth (http://www.whatonearth.co.uk/).

Many books about volcanoes deal with Krakatau. I suggest you try:

• Volcanoes by John Francis.
• Krakatoa by Rupert Furneaux.
• Krakatoa – the day the World exploded by Simon Winchester.

Other parts of this article:
Krakatau – Part 1
Krakatau – Part 2