After G W Bush's "mission accomplished" event on the deck of the aircraft carrier involved in the Iraq invasion, I'll never utter these words without a question mark after them. With the question mark added, they are apt for our last day here. We think we've got a great set of samples to bring home. The map I'm including shows they're well distributed across the island. But until we do the work in the lab, we won't really know if we've accomplished the mission.
Dave's idea of packing for a big overseas field trip is to find old shoes that are about die, and to wear them until they die. This seems risky to me, but at least means he doesn't have to clean them to get back into NZ.
Today was our last full day on the island, so Dave went for a long hike. When he returned, he pronounced his shoes to be dead.
Today was our "day off" again, which meant we started packing and writing our report.
I thought I'd tell you about the mana vai which the people of Rapa Nui used, and still use, to grow crops. Within stone walls, the plants are well protected from the wind; this conserves water (vai). This is very helpful for the more tropical plants brought from Polynesia. Here our guide Soro has ginger in one hand and a sugar cane in the other. Mark and John were impressed, and there's more sugar cane behind John.
The other photo shows a much tidier mana vai, which we saw in the same area while we were looking for places to sample soil.
Today we sampled a site quite some distance around the north coast. Here's a view of our site (with a calf for scale), which contained about 2 meters of nearly rockless soiI. It took researchers a long time to recognize that all these rocks were put in place by people to reduce water losses from cultivated plants. Amazing, eh?
Today we're continuing with more soil coring. I'll post some photos of this tomorrow.
I thought I'd post today about improvisation. Working in a remote place often involves some improvisation. There have been many ways we've improvised on this trip, and here's one. Normally, we like to dry samples in nice ovens, or better yet in freeze dryers. For samples that had to be dried here, I "built" this cute little oven. It consists of a box with a hole cut in the bottom to go over a light. With the help of a tripod and an extra bed, the box was stable for an
overnight drying session. And as you can see from the lower reading, it hit my target range of 35-40°C nearly perfectly.
Warning: be careful with heat. I checked the temperature around the light bulb quite a few times to be sure I wasn't a fire hazard. John reports that an older tactic was to use a candle as a heat source, and he caught his plant samples on fire once!
As our soil sampling has proceeded, we've been able to refine our visual target for sites. We're trying to find sites that naturally collect sediment from a significant uphill area with both human occupation and agriculture. As we've proceeded, our skill has improved at finding sites that collect sediment efficiently without being scoured out during major floods. This site was nearly ideal. It samples a large area upstream of gorge in the background.
The exact location we sampled showed evidence of almost continuous soil burial, but had to be chosen carefully because areas directly downstream of the gorge appeared to be scoured out during floods.In the sample shown, the core is composed entirely of material dark enough to be a topsoil, but the sample is from 1.2 - 1.5 m below the soil surface. Throughout most of the island, soils at this depth would be light reddish brown.
Studies of lake sediments and climate at Rano Raraku -- the crater where nearly all the moai (statues) have been carved -- have suggested that lake level was once higher (at the end of the last glacial period). In the process of identifying soils to sample, we've stumbled onto what seems to be previously overlooked evidence for a high stand of lake level. In addition to large areas of "ironpan" development consistent with a vegetated peaty lakeshore, we found large numbers of fossil roots which we can use to partially identify the plants that once occupied the lakeshore.
With the benefits of good access and additional help, we were pleased to finish off our coring here in only two days. Here you can see our coring raft on the lake.One of the most remarkable aspects of the crater (after the moai of course) is the rapidly eroding red soils. The red soils are diagnostic of volcanic terrains in the tropic and subtropics. The erosion here is interesting, because it is relatively rare to see such pronounced erosion on the island -- despite the reputation Easter Island has for erosion, I remain unconvinced the problem is as serious as in many other parts of the world. In Rano Raraku however, I'm amazed by he energetic herds of wild horses with dust flying behind them. They must be both drawn and energized by the water source. As Mark puts it, they are "just horsing around."
Today, we began coring Rano Raraku, the crater lake around which almost all the moai were carved. Rano Raraku has been cored more than any other lake on the island, partly due to interest in the statues and partly because it yields beautiful sediment cores. Most of all, access is easy.
For us, Rano Raraku meant a contrast from working in the open on a floating vegetation mat. We were cooped up on a very small raft for the entire day. Today's photo shows a silhouette of David efficiently operating the corer. In the background, you can see the open 9-10m core and 9m of core neatly stacked in boxes.