Final answer:
Among the options given, basaltic (mafic) lava would be the least expected to find at Mount Vesuvius, as Vesuvius is known for more explosive eruptions producing felsic rather than mafic lava.
Step-by-step explanation:
The violent eruption of Mount Vesuvius in 79 C.E. led to the burial of Pompeii under vast amounts of volcanic material. Given the catastrophic nature of this eruption, one would expect to find evidence of volcanic ash, pyroclastic flows, as well as the solid remains resulting from these, like pumice and other types of tephra. However, based on the composition of lavas typically emitted during these types of highly explosive eruptions, which is usually felsic due to the high viscosity and trapped gases, one would least expect to find basaltic (mafic) lava at Vesuvius."
Basaltic lava is typically associated with less explosive, more effusive eruptions, characterized by lower gas content and higher temperatures, which makes it much more fluid. Vesuvius, on the other hand, is famous for its more silicic, rhyolitic lava, which contributes to the explosive nature of its eruptions due to higher silica content, making it more viscous and trapping more gases. In the eruption of 79 C.E., the presence of pyroclastic flows, volcanic ash, and the preservation of Pompeii and Herculaneum support the expectation of rhyolite rather than basaltic lava.