A temperature measurement probe into the melt of the Kilauea Iki Lava Lake in Hawaii

In October 1961 a hole was drilled through the 35-foot crust on Kilauea Iki lava lake, and a hollow stainless steel-mullite probe containing a thermocouple was forced 4 feet into the underlying melt. Observations made during emplacement of the probe permit the base of the crust to be identified as the 1065°C isotherm. The maximum temperature measured in the molten lava was 1106°C. The thermal gradient in the liquid was 5°C per foot, and the cooling rate for a 22-day period was 0.5°C per day at a depth of 39.2 feet. After the first 8.1 months, the average rate of crustal thickening for a 13.3-month period was 0.94 foot per month.