Natural Sun Firefall
This is not Lava! It is the reflection of the sun. This was an amazing spectacle to witness. Happening only two weeks out of the year, the setting sun falls behind the vertical face of El Capitan, selectively lighting this waterfall with its orange sunset light.
Gradually growing in intensity and color for the last 5 minutes or so, it was like seeing a narrow strip of lava flowing down the face of El Capitan.