Minecraft wiki entry for Lava, associated text: Lava's melting pattern for snow and ice.
A natural lava spring near a waterfall.
The lava "ocean" layer of caves.
A naturally-occurring stream of lava next to diamond and iron ore.
The warning in Legacy Console Edition when trying to place lava near the spawn point.
A running lava source (origin not seen) uncovered six blocks below the surface of desert terrain.
The inside view of lava with the night vision effect.
Ladders can stop lava from flowing.
A lava spring.
Lava spreading into dirt.
Lava in a ravine.
Lava found in a snowy ravine.
Lava generates on bedrock.
Lava being extinguished near bedrock.
Lava pool and water pool meeting each other naturally.
Two lava springs meeting water in a savannah plateau.
Lava spreading in the Overworld.
A lava spring spreading into a lava lake.
Sugar cane growing with lava flowing around it.
Tall lavafall flowing into ravine.
Ravine with multiple ores, water and lava falls, and stronghold bridge over it.
Another example of underground lava lake.