English: A simplified version of the conceptual models showing typical CO₂ emission patterns from volcanic and magmatic systems. CO₂ may be sourced from magma bodies deep in the crust, whereas other volatiles may remain largely dissolved in magma until much shallower depths. Visible plumes are typical for active volcanoes, whereas CO₂ degassing from dormant/inactive volcanoes and hydrothermal systems is less obvious. Low-temperature degassing may or may not result in a visible plume even when CO₂ is present. Significant quantities of CO2 are emitted from areas of diffuse degassing, and CO₂ also reacts with groundwater.