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.
CONAF has asked us to take a native guide with us each day. This serves two purposes. First, the guide will keep an eye on us and make sure we don't do anything we shouldn't -- there are so many archaeological artifacts and sites here, this is more useful than it may sound. Second, the guide knows the island extremely well. It was suggested that we take a guide named Zoro who has worked with scientists and archaeologists his whole life, going all the way back to William Malloy (still regarded as the greatest archaeologist to work here). I was briefly resistant to the idea of having a guide that doesn't speak hardly any English (because we speak hardly any Spanish), but amazingly we seem to understand each other very well because of his experience working with scientists. Nevertheless, I am making it a priority to try to learn some more Spanish as fast as possible.
Today we looked at Rano Aroi and other depressions on the largest mountain on the island. These depressions collect the sediments we want to bring back to the lab to analyse. The depressions here will help us understandithe highest elevation areas, which we think were the last to be deforested. Previously, work here has focused on the crater at Rano Aroi which has a large swamp. Unfortunately, there was an effort to clear away the upper meter of peat some years ago and previous results suggest that it may or may not still contain sediments that will give us the results we want. Luckily in several hours of walking, we found areas that appear likely to give us excellent records from the last 1000 years.
We then proceeded into the crater at Rano Raraku, where the moai (statues) were made. This site has proven most popular to core, for reasons that may be obvious from today's photo - be sure to note the moai in the background. With a lake sediment core, we look backward in time as we go down. In each layer of sediment from the lake, pollen, soil and all sorts of other biological and chemical markers tell us what the surrounding environment was like when that layer formed. So, it has proven possible to work back through time, identifying when the forest around the lake was cleared, and when massive statue building activity was underway, as well as when European introductions of trees and grasses occurred.