Edge of the Volcano

You stand on the Western rim of an active caldera, facing South.

Behind you is a glowing orange portal that prevents you from walking along that side of the rim. If you understood the Professor correctly, entering the portal will probably reset this puzzle.

The rim continues South, and the non-lava side of the mountain is to your West. It looks too steep to climb down right here, however.

Walk South along the rim.

Why not jump into the lava and go for a swim?

Head North back into the portal.