Minecraft wiki entry for Obsidian_farming, associated text: In the Overworld, lava primarily occurs deep underground or at the bottom of ravines. Sometimes part of these pools will be drenched by a natural water spring. However, it can occasionally also be found in small lakes, at or near the surface. It is also possible to find small lava springs, but since these typically only contain a single source block, they are not particularly useful. It also occurs at the bottom of ocean ravines, where it is normally immediately drenched by the water over it.