Understandable Earth Science

Welcome to Part 3 of my blog sharing some of my Indonesian fieldwork experiences as part of the Soa Basin Project. My previous post described life on the archaeological excavations in the Soa Basin, but a lot of the work I did was spent further afield, hunting down layers of volcanic deposits that could be used to correlate between different excavation sites. Most of the time, I was working with my colleague Ruly, a geologist at Badan Geologi (The Geological Agency of Indonesia) and University of Wollongong PhD student, who appears in many of the photos below. This blog entry describes some of the fieldwork conditions; I’ll cover more about the geology and volcanoes of the area in a later blog post.

Out in the field, it was hot. So hot that I started strapping bottles of water to the outside of my bag and by lunchtime it was warm enough to make a decent cup of coffee with. One of the first rules of working in the tropics is to seek out shade wherever possible. You know the way a cat will find and sit in the patch of sunlight coming through a window? In the field, we do the opposite. That wasn’t always possible, and we would sometimes have to collect pumice samples from white cliffs of volcanic tephra in direct sunshine. Needless to say, it was hot and sweaty work! But it turns out that volcanic dust makes an excellent sunscreen – I never got sunburnt on sampling days.

Lunch in the field was usually similar to dinner – sandwiches aren’t really a thing in Indonesia, so we would pick up a bag of rice and baked fish and / or chicken in the morning to take with us. On particularly hot days the food would be hot by lunchtime, as though it had only just been cooked within the last half an hour  (thankfully and surprisingly, we didn’t get food poisoning).

There were two main types of field terrain in my field area. The centre of the Soa Basin is generally flat, but with deeply incised river canyons; a lot of vegetation had been cleared in the past for farming and cattle grazing, giving a dry, scrubby grassland that is easy to navigate. The edge of the basin is host to many volcanoes – some of which have erupted historically and some of which are probably extinct. Much of the area around these volcanoes is densely vegetated jungle, probably because the volcano flanks are so steep they aren’t worth clearing for agriculture.

01c SoaVolcanoes

Google Terrain map showing the volcanoes surrounding  the Soa Basin

During my first field season, we thought it would be a good idea to explore the surrounding volcanoes to collect samples and start building up a geochemical database of local volcanism. Most of these volcanoes are steep sided and covered in tropical rainforest or tall grass and a lot of the time was spent hunting for rock exposures (sometimes without success). I didn’t have my own machete (not the easiest thing to take on a plane…) and so Ruly did most of the Bushwhacking; seeing his back disappearing into the jungle became a very familiar sight.

The grass on many volcano flanks was deceptive. From a relatively close distance, it looked short and easy to walk through and there were many times when we aimed for this kind of terrain (like the hill in the background above-left), thinking it would be easy walking. But when you get closer, the grass turns out to be 1-2 m high and even harder to walk through than the jungle-vegetation.

One day, we spent over 2 hours fighting our way through just 400 m of this grass to reach some rocks exposed at the top of a small satellite cone on the flanks of Keli Lambo. (Annoyingly, we then had to make the same journey back again, but this time laden with rock samples). Another day, we were lucky enough to find an irrigation channel running through the jungle inside Welas Caldera, that we were able to walk along the top of, with minimal bushwhacking. We managed to not fall into the channel, but unfortunately didn’t find any rock exposures to investigate.

Often the best exposures were in river channels and these sometimes contained spectacular dried up waterfalls. I was itching to get a closer look at the stratigraphy exposed in these cliffs, and sometimes we were able to safely find our way to the base of the exposure, but often they were too steep to access without rock climbing equipment. Sometimes, the jungle in these dried up river canyons was so dense that we struggle to get a GPS reading once we had managed to find some rock exposures to sample.

Other times, rocks were exposed in rivers that hadn’t dried up, and these often gave us some fun close encounters with the local “wildlife”.

Away from the rivers, wildlife encounters were still common, especially with arthropods. I learnt early on to be very careful when handling interesting looking rocks, after finding a scorpion on the underside of a rock I had picked up to look at more closely (I probably should have already realised this, after finding a scorpion in my bed).

Then there were the spiders! Apart from the Huntsmen that hung around one of the houses we stayed in, I didn’t see many spiders on Flores. But the ones I did see were impressive. I have seen the stripy orb-weaver spiders before and *almost* find them more beautiful than I find them scary. I saw a couple of these hanging on webs in dried grass, usually next to a path.

The only other spiders I saw in the field were so terrifyingly big, they stopped me from sampling a lava flow exposed in a stream cutting. We were looking for rock exposures to sample on Ambulobo and spotted an exposed lava in a dry waterfall behind a bridge. We spotted a route down from the road to the river bed, but there was a massive spider web hanging over the gap in vegetation that would be the river in the wet season. On this web were three absolutely massive spiders – each had a leg span of about 20 cm (take a ruler, look at how big 20 cm, and then imagine the above photo as that size!). They were black and red and looked evil (although I have since been told that that they are just harmless orbweavers). I decided that we could probably manage without that lava sample. Ruly was much braver than me!

Other encounters included a creature that built itself a cage before turning into a chrysalis, and giant grasshoppers.

Most of the time it was just me and Ruly in the field along with our driver (one of the local people who owned a 4WD truck and hired it out to the Soa Basin project). But we often met people while in the field, even in the middle of the jungle. It wasn’t uncommon to find a family farm, or even a small traditional village. Most of the time people were friendly and helpful and we sometimes hired them for a few hours to show us the way to rock exposures. One family fed us cups of tea and deep fried peanuts while we were waiting for our driver to pick us up, and the mother gave me a beautiful tobacco bag that she had made. Another time, while we were examining an exposure fairly close to a road, a truck full of people spotted us, stopped and then insisted we take their photo(?).

Overall, the fieldwork was hard work, under quite difficult conditions. But the friendly people we met in the field, combined with the consistently stunning landscapes of the area made the work enjoyable (even when I spent all day becoming increasingly covered in volcanic ash whilst sampling).




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