features, geologically-speaking, the Savute Marsh, the sand ridge, the Savute channel and some isolated rocky outcrops. The large number of dead trees is surprising. Although the Savute Marsh becomes marshy temporarily in the wet season, this is insufficient to explain the wooden graveyard. In fact, at certain times water has flowed in through the Savute Channel flooding the marsh and killing the trees. The channel is known to have been dry between about 1888 and 1957. After that it flowed until 1979, except for 1966-7. Since then it has been dry, but it continues to support highly nutritious grasses which attract thousands of herbivores. It is believed that the erratic flow is caused by tectonic plate movements. The channel has a slope of only 18cm per kilometre, so it takes little movement of the earth to stop, or start, the flow.