We describe volcanic inverted relief sites around the world, making a comparative
analysis of those most significant sites found from literature and our own search
on imagery and global topographic maps. Over fifty significant areas of volcanic inverted
relief were found. The comparative analysis is based on geoscience values defined
by the main geological and landscape elements that define inverted relief. This subjective
analysis is open and can be verified and extended if other significant sites emerge,
thus forming the basis of a future, exhaustive global comparison of this important
geomorphological feature. Inverted relief occurs when valleys transform to ridges
due to differential erosion of relatively resistant valley-fill, and weaker slope
lithologies. It is found in various geological settings, and it is very common in
volcanic terrains, especially monogenetic volcanic fields, where most examples are
inverted lava flows. Relief inversion provides a clear indication of slow geological
changes and landscape evolution through erosion and can be thought of in popular terms
as a geological clock. Volcanic inverted relief was recognised in the 18th - 19th
centuries in the Chaîne des Puys (Auvergne, France), and used as evidence to first
support plutonism by Nicolas Desmarest and then support uniformitarianism by George
Poulett Scrope. We review the geological and geomorphological features of volcanic
inverted relief world-wide, with an emphasis on the classical Auvergne. We explore
how volcanic relief inversion chart geological changes, and their value for studying
geological systems and landscape evolution. With our comparative analysis we can propose
sites with the greatest geoheritage potential for representing inverted relief globally
and suggest how this can be valued as geoheritage. As volcanic inverted relief is
an important sub-set of all inverted relief, and is generally associated with important
surface, volcanic and tectonic processes, and is often ongoing, it can be an important
geoheritage component in natural sites. We suggest that it should should be present
in the International Union of Geological Sciences (IUGS) Global Geosite list, can
be a component of geosites in UNESCO Global Geoparks. It is also a feature for geological
criteria (viii) in UNESCO World Heritage sites, where it fulfils all the requirements
being both a major geomorphological feature and a fingerprint of significant geological
processes in Earth evolution.
