This study focuses on Ravenna during the period from its fall into the hands of the Lombards in 751 to the decline of Byzantine power in the West from the mid-eleventh century. It argues that Ravenna shared common features with a number of other cities in the upper Adriatic, for example Comacchio, Venice and Zadar. The city maintained its earlier economic and artistic ties with Istria and Dalmatia, but also with Constantinople. The ties to Byzantium were based on admiration, nostalgia or identity and were used as part of strategy of resistance to threatening outside forces. However, the increasing dominance of local landowning elite led to the local autonomy and the strongest Byzantine influence remained the social and cultural cachet of the empire.

This chapter reviews the systematics of partial melting of mantle lithologies – like peridotite and eclogite – in the presence of carbon dioxide. It discusses the composition of mantle-derived magmas generated in the presence of carbon dioxide and whether magmas erupted on Earth’s surface resemble carbonated magmas from the mantle. It reviews how the production of carbon dioxide-rich magma in the mantle varies as a function of tectonic settings – beneath continents and oceans and in subduction zones – and time.