Abstract
This paper describes the results of analogue experiments of the inflation and deflation of a vertically elongated magma chamber. The model comprised a balloon (analogue magma chamber) buried in starch powder (analogue crust).
The main results of the experiments are as follows:
1. Minor funnel collapse (apical-graben type) is caused by inflation of a vertically elongated magma chamber. The diameter of the collapse zone is 0.8-1.6 km in natural scale, possibly too small to be considered a caldera.
2. The deflation of a vertically elongated magma chamber produces a flat-floored caldera with a small area of central collapse. The natural size of the caldera is estimated to be 0.9-4.4 km in diameter and 200-400 m in depth. This model may provide an analogue of the Kilauea caldera.
3. Compared with a purely deflation model, a smaller amount of caldera subsidence results from inflation and subsequent deflation of the magma chamber, probably due to crustal dilatancy following pre-caldera doming.
