For me, it’s Chile: there are over 100 active volcanoes, most of which have never been studied. The part where I am working now, in the south between about volcan Llaima and volcan Hudson, is also ideal for three other reasons:
– the volcanic chain runs approximately north-south, while the winds usually blow west to east. So it’s quite easy to find ash deposits from each volcano, and to start to put these into a time sequence;
– there are a lot of lakes in the region. Any ash that falls into these lakes is preserved as a layer in the sediment, and slowly gets buried over time. We can use mud cores collected from these lakes to study the record of past volcanism (ash layers) and climate (from the mud layers, and lake fossils) over the past 20,000 years.
– the region was covered in ice sheets until 15-20,000 years ago; the ice then retreated at the end of the ice age. This is an ideal place to see what happens to volcanoes when they are first covered in ice, and then what happens as that ice is lost.