This open access book summarizes the findings of the VUELCO project, a multi-disciplinary and cross-boundary research funded by the European Commission's 7th framework program. It comprises four broad topics: 1. The global significance of volcanic unrest 2. Geophysical and geochemical fingerprints of unrest and precursory activity 3. Magma dynamics leading to unrest phenomena 4. Bridging the gap between science and decision-making Volcanic unrest is a complex multi-hazard phenomenon. The fact that unrest may, or may not lead to an imminent eruption contributes significant uncertainty to short-term volcanic hazard and risk assessment. Although it is reasonable to assume that all eruptions are associated with precursory activity of some sort, the understanding of the causative links between subsurface processes, resulting unrest signals and imminent eruption is incomplete. When a volcano evolves from dormancy into a phase of unrest, important scientific, political and social questions need to be addressed. This book is aimed at graduate students, researchers of volcanic phenomena, professionals in volcanic hazard and risk assessment, observatory personnel, as well as emergency managers who wish to learn about the complex nature of volcanic unrest and how to utilize new findings to deal with unrest phenomena at scientific and emergency managing levels. This book is open access under a CC BY license.

This volume aims at providing answers to some puzzling questions concerning the formation and the behavior of collapse calderas by exploring our current understanding of these complex geological processes. Addressed are problems such as:
- How do collapse calderas form?
- What are the conditions to create fractures and slip along them to initiate caldera collapse and when are these conditions fulfilled?
- How do these conditions relate to explosive volcanism?
- Most products of large caldera-forming eruptions show evidence for pre-eruptive reheating. Is this a pre-requisite to produce large volume eruptions and large calderas?
- What are the time-scales behind caldera processes?
- How long does it take magma to reach conditions ripe enough to generate a caldera-forming eruption?
- What is the mechanical behavior of magma chamber walls during caldera collapse? Elastic, viscoelastic, or rigid?
- Do calderas form by underpressure following a certain level of magma withdrawal from a reservoir, or by magma chamber loading due to deep doming (underplating), or both?
- How to interpret unrest signals in active caldera systems?
- How can we use information from caldera monitoring to forecast volcanic phenomena?
In the form of 14 contributions from various disciplines this book samples the state-of-the-art of caldera studies and identifies still unresolved key issues that need dedicated cross-boundary and multidisciplinary efforts in the years to come.
* International contributions from leading experts
* Updates and informs on all the latest developments
* Highlights hot topic areas and indentifies and analyses unresolved key issues