Mossy pool, warm and still, where geothermal waters seep up.
Thermal Spring is a muted green, close to teal.
It can be described as muted, dull, matte and soft.
Set in black, because black reads best on it.
A hot spring, thermal spring, hydrothermal spring, or geothermal spring is a spring produced by the emergence of geothermally heated groundwater onto the surface of the Earth. The groundwater is heated either by shallow bodies of magma or by circulation through faults to hot rock deep in the Earth's crust.
Read on WikipediaA thermal column is a rising mass of buoyant air, a convective current in the atmosphere, that transfers heat energy vertically. Thermals are created by the uneven heating of Earth's surface from solar radiation, and are an example of convection, specifically atmospheric convection.
Read on WikipediaNoun