СИ-2017

[Евгений Машеров]

"На диване" на вопрос 2-400 я ответил "углекислый газ", выслушав ответ, отметил неполноту своих знаний, но на всякий случай полез в энциклопедию.
Углекислый газ и метан.

In Lake Kivu's case, methane and carbon dioxide due to lake water interaction with a volcano. The amount of methane is estimated to be 65 cubic kilometres. If burnt over one year, it would give an average power of about 100 gigawatts for the whole period. There is also an estimated 256 cubic kilometers of carbon dioxide. The water temperature is 24 °C, and the pH level is about 8.6. The methane is reported to be produced by microbial reduction of the volcanic CO2. The risk from a possible Lake Kivu overturn is catastrophic, dwarfing the historically documented lake overturns at Lakes Nyos and Monoun, because approximately two million people live in the lake basin.

Сероводород не упоминается.