A raised lava lake, described by volcano scientists as looking "somewhat like an above-ground swimming pool," has been building since lava returned to Pu‘u ‘O‘o crater in March, scientists from the Hawaiian Volcano Observatory reported.

The rim of the raised lava lake was about 30 feet higher than the surrounding crater floor, which was 170 feet below the eastern crater rim as of Wednesday.

The rim has been progressively built up by overflows of lava that have cooled and solidified. A few breaches of the fragile upper rim have allowed lava to pour into the surrounding low areas between the crater walls and the perched lake before resealing itself.

On Friday, the Hawaiian Volcano Observatory released a time-lapse thermal image of the lava in Pu‘u ‘O‘o, which shows the lava lake forming over the past two months.

Lava drained from Pu‘u ‘O‘o on March 5 during the Kamoamoa fissure eruption and remained absent for several weeks. The thermal camera images show the abrupt return of lava to the crater floor on March 26, followed by activity that led to the development of the lava lake.