Volcanologist.
A geologist or marine geologist would study underwater volcanoes. They would analyze the eruptive history, composition of the lava, and the geological processes involved in the formation of underwater volcanic structures.
A paleontologist would generally study paleontology.
The type of investigation would be fieldwork.
Oceanogarphers study the oceans geography, but there are many other types of jobs that study things such as fish and volcanoes under the waves.
A volcanologist or a geologist specializing in volcanoes would be most likely to study the cooling of lava after a volcanic eruption. They would investigate the physical and chemical properties of the cooling lava to understand its behavior and how it solidifies over time.
Geologist - specifically a 'Vulcanologist'
a physicist
zoologists
An archaeologist
Geologists study the Earths surface
all of them
BIOLOGISTS ...