Hot and toxic - hydrothermal vents

Hot vents occur where there are volcanoes in the ocean. How hydrothermal vent evolve is described here: Seawater (1) infiltrates deep down into the Earth’s crust through cracks and fissures in the so-called recharge zone (2). Close to the magma chamber it gets extremely heated. Metals and hydrogen sulfide get dissolved out of the rock. The thermal fluid rises in the so-called discharge zone and gushes out of the rock as hot vent. The hydrothermal fluid with its temperature up to 350° - 400° Celsius mixes with the cold seawater. Gypsum and metal sulfides, like iron sulfide (pyrite or fool’s gold) precipitate (forms into particles). Chimneys are formed this way and hot hydrothermal fluid with black precipitates (called Black Smoke) gushes out of the chimneys. When the thermal fluid already mixes with seawater in the Earth’s crust, warm thermal fluid pours out of the basalt. This vent then is called a warm vent.

The hydrothermal fluid also contains a lot of the gas hydrogen sulfide. This gas is poisonous for most creatures, including human beings. Our scent detects this poison even at very low concentrations and warns us. It smells like rotten eggs. Most of the animals of hydrothermal vents live at warm vents.