Professor Cook says the tree-ring records show periods of wet and dry weather.

VOA: special.2010.05.25

Indonesia is on the so-called Pacific Ring of Fire where several tectonic plates meet and often cause earthquakes.

VOA: standard.2009.09.03

Using a hollow tube, they drill into the tree and extract a 5-mm wide cylinder that shows each ring starting with the most recent, just under the bark.

VOA: standard.2010.04.05