Improving forecasting of the timing, location, size, and impact of eruptive hazards is a top priority of the volcanological community. Surface deformation in volcanic systems can give insights into sources of volume or pressure change in the subsurface and allows us to develop hypotheses of likely drivers of that change. Large questions remain, including: When is deformation caused by magma? When does deformation lead to eruption? How does frequently changing deformation impact an eruption? Additional datasets such as gravity, topographic change, and seismicity can complement surface deformation data to begin to answer some of these questions. In this dissertation, I investigate the use of surface deformation and topographic change datasets in studying volcanic activity and how they could be related to an eruption. First I seek to answer questions about the nature of magma versus volatile movement in the volcanic system of the restless Pleistocene volcano Uturuncu (Bolivia) to better understand if the unrest could lead to an eruption. I track Uturuncu’s recent deformation using interferometric synthetic aperture radar (InSAR) data and the global navigation satellite system (GNSS) station UTUR, located near Uturuncu’s summit and find evidence of shallow and deep sources of activity. I use these data along with a subsurface resistivity model to develop a conceptual model of a transcrustal magma system at Uturuncu. I attribute the surface uplift to pressurization from ascending gasses and brines from magmatic reservoirs in the midcrust and the surface subsidence to a collapsing network of brine lenses in the shallow hydrothermal system. I then take a global approach to investigating the spatial and temporal scales of topographic change during eruptions. Up-to-date topography data are essential for forecasting volcanic hazards and monitoring deformation. Digital elevation models are used to quantify eruption rates, model flows, and accurately process other monitoring datasets. Despite this global need, we do not know the characteristics of topographic change at volcanoes over a given time interval. I generate a database of volcano topography change over the last forty years of large eruptions and develop recommendations for optimal spatial resolutions and frequencies at which to collect these data. I conclude with two chapters on the 2016-2022 Nevados de Chillán, Chile eruption. This complex eruption has multiple phases of surface deformation and effusion, which I document with ground-based, aerial, and satellite data. There were a total of four domes and eight flows erupted through the course of the eruption. I combine a decade of pre-, co-, and post-eruptive InSAR time series data with 4.5 years of co-eruptive data at five local GNSS stations to define three distinct periods of co-eruptive surface subsidence and three periods of co-eruptive surface uplift. I model the surface deformation during the eruption, generate a conceptual model of the sources driving deformation, and use effusion rate and seismicity to better understand the physical drivers of changing behavior. This collection of global and case studies adds to the scientific understanding of the scales and complexity of activity we see at volcanoes. The combination of ground-based, airborne, and satellite-derived datasets provide temporally and spatially dense information about volcano and eruption evolution, bringing us closer to understanding the physical mechanisms that drive changes in behavior.