Obsidian is a volcanic product that forms under particular geological conditions, and hence occurs in limited areas of the Earth. In ancient times, obsidian was used successfully by various peoples to produce artistic artefacts, but also to make tools and weapons used in everyday life. For this reason, obsidian was transported from geological sources to other locations. The study of methods used to identify the provenance of obsidian artefacts has become crucial for understanding commercial relations between distant ancient populations. Other volcanic products, generally associated with obsidian, are volcanic glass shards. Glass shards were used in Mexico as aggregates to produce plasters, and recent studies have shown that they were also transported along commercial routes. This chapter presents an introductory overview of the sources of obsidian in the Tyrrhenian area, showing how minor, trace and rare earth elements can be used to solve provenance problems. A case study regarding the provenance of glass shards inside archaeological plasters taken from Teopacazco (Teotihuacan, Mexico) is also presented.

Geological mapping of the island of Lipari at 1:10,000 scale was performed by adopting a stratigraphic approach based on the integrated use of lithostratigraphic units, lithosomes, and unconformity-bounded units. This approach allows the geological peculiarity of this volcanic area to be reproduced through documention and interpretation of the different rock types (using lithostratigraphic units), and definition of the geometry of rock bodies (using lithosomes), with emphasis on unconformities in the volcano-sedimentary architecture (using unconformity-bounded units). In particular, by concentrating on accurate tephrostratigraphy and deposits formed during periods of prolonged volcanic quiescence (e.g., marine deposits and epiclastic products), unconformity-bounded units provide the main stratigraphic constraints at a regional level. Two first-order unconformities (U I and U II ), represented by surfaces of erosion bounding marine deposits emplaced during marine oxygen isotope stage (MIS) 5, can be correlated across most of the Aeolian archipelago. Furthermore, four second-order and seven third-order unconformities represented by erosion and non-deposition surfaces formed during main periods of dormancy or minor sea-level fluctuations of MIS 5 are introduced. The reconstructed unconformity-bounded stratigraphy, together with other rock-stratigraphic units, provides an effective reconstruction of the geological evolution of Lipari, ranging between ca. 220 ka and the present time, as the result of the interplay among volcanic activity of local and external provenance, sea-level fluctuations, and regional fault systems. In this framework, Lipari's eruptive history encompasses five successive eruptive epochs characterized by distinctive centers of eruption (eastwards shifting), eruption type (from mainly strombolian to hydromagmatic), and chemical composition (from calc-alkaline basalt-andesite to high-K calc-alkaline rhyolite).

Silicic volcanism in the central Aeolian Islands of Lipari and Vulcano has followed a consistent pattern during the past 22,000 years. Active eruptive cycles generally began with hydrovolcanic breccias, surge beds, and ash-fall deposits. They ended with magmatic effusions that formed lava domes and short coulees. Long repose periods separated shorter active cycles. Eruptions occurred from both isolated vents located along fissures (e.g., domes of southern Lipari) and central vents with a long history of activity and repose (e.g., Fossa cone of Vulcano). The compositions of the juvenile products include leucite tephrite, trachyte, and rhyolite. The average volume of silicic products in an eruptive cycle on Lipari and Lentia was about 5 × 10 8 m 3 of juvenile magma. The repose period between major active periods was about 4,000 years. The production rate for the period of 22,000 years ago to the present was 10 5 m 3 per year. The average volume of erupted material in an active cycle at Fossa (other than the Punte Nere cycle) was about 2 × 10 7 m 3 of juvenile magma. Repose times between cycles range from 300 to 800 years. The rate of magma production for the entire Fossa cone during its 6,000-year growth was 5 × 10 4 m 3 per year. Vulcanello produced about 3 × 10 7 m 3 of tephritic to trachytic magma in the past 2,100 years, a production rate of 1.5 × 10 4 m 3 per year.