During a 36-day eruption in 1959, the Hawaiian volcano Kilauea produced rivers of red-hot lava that filled the adjacent crater, Kilauea Iki, to a depth of 135 m (440 ft) and created a lake of molten rock. The Kilauea lava lake provided scientists with a natural laboratory and a rare opportunity: a chance to observe lava slowly crystallizing. From 1959 through the early 1990s, they closely monitored the lake as it cooled and solidified.

		Surface In August of 1967, geologists prepare to drill through the crust of the partly solidified lava lake.
		48.3 Meters This sample, which was relatively close to the lake’s surface, had completely crystallized by 1979. The large white crystals are olivine. They are surrounded by smaller crystals of pyroxene (brown), prismatic plagioclase (white), and titanomagnetite (black).
		51.9 Meters At this depth, the lava still contained 18 percent liquid (now brown glass) in 1979. Mineralogy is the same as for the uppermost specimen.
		53.1 Meters Deeper and hotter, the lava was 24 percent liquid (now brown glass) in 1979. Mineralogy is the same as for the uppermost specimen.
		55.6 Meters Deep within the lake, the lava was 31 percent liquid (now brown glass) in 1979. Notice that the black titanomagnetite visible in the other photos had not yet started to crystallize. Otherwise, the mineralogy is the same as described for the uppermost specimen.