volcanologists

"Volcanic ash, despite the name, is dense as rock and can cause significant damage to structures, power lines and communications. It is also toxic because it contains chemicals such as sulfur, chlorine or fluorine, and it can therefore affect water supplies."

"When (volcanic) ash falls into the ocean, it brings with it nutrients. For example, It can bring iron, which is usually quite low in the ocean. It can suddenly create a bloom of plankton, which then go through the food chain, creating a population boom later on the fish and other lives too."

"At the recent La Palma eruption in the Canary Islands, we had a classic signal that something's going to happen (on its volcano). There was a scattering of earthquakes slowly moving up towards the surface to a particular spot. There also could be gas emissions, or increased temperatures of surface water, or the ground inflating slowly­ – these things can be detected by satellite. But most of the data that serve to warn scientists of an impending eruption are collected by instruments around the volcano. (However) Gathering that data is very difficult in the case of submarine systems (2022 Tonga volcano eruption case)."