Taupo volcano's restless nature revealed by 42 years of deformation surveys, 1979-2021

Lake Taupo, New Zealand, conceals a large caldera volcano which last erupted in 232 AD. A surveying experiment in 1979 which utilised the surface of the lake for detecting small movements of the lakebed soon became a programme to monitor vertical deformation by making regular observations at 22 fixed points - survey stations - around the lake. The programme continues today with 4 surveys being made annually. In this paper, we review the methodology and present the 42 year-long dataset in graphical forms, and draw conclusions on its implications in terms of volcanic and tectonic deformation. We also make the dataset available for download. The dataset confirms that vertical deformation is occurring in the lakebed. Long periods of slow deformation, dominated by subsidence totalling 140 mm in the Taupo Fault Belt at the northern end of the lake, and to a lesser degree at the southern end, are interrupted by uplift episodes now reaching 160 mm in the northeastern sector containing the most recent active vents. We suggest that the subsidence is primarily tectonic while inflation episodes are driven by upward migration of magma to shallow levels during periods of unrest.