In Kilauea volcano in Hawaii Island (Fig. 1), a fissure eruption occurred in lower Puna district on the foot of the East Rift Zone on May 3, after a collapse occurred at Puu Oo crater on April 30, 2018 (United States Geological Survey). On 17th, an explosive eruption occurred at Halemaumau crater which lies in the caldera on the summit of Kilauea. Even after this, the fissure eruption in lower Puna district continued causing many cases of damage including burning-down of houses in the vicinity.
Fig. 1. Locations of Kilauea volcano and the East Rift Zone. The size and range correspond to that shown on the images of "Shikisai" in Fig. 2.
Images of "Shikisai" were able to observe those activities of Kilauea volcano. Fig. 2 shows occurrences of lava flows observed by the infrared images. In the image on May 5, thermal anomalies are noticed in the caldera on the summit of Kilauea (including Halemaumau crater) and in PuuOo crater. These seem to be due to temporary increase in thermal emission in the areas relating to the collapse or eruption events. In addition, weak thermal anomalies (arrows) lined in the east-northeast - west-south-west direction, the same direction as that of the East Rift Zone, is recognized in the lower Puna district. These are considered to be the occurrence point of the fissure eruption and its deposits in the early stage. In the image on 16th, it is observed that the thermal-anomaly areas expand and extend east-northeastward, which suggests that the activity is becoming active. Furthermore, it can be seen that the flow front of a lava flow turning southward and starting flowing down on the slope. In the image taken in late May, the lava flow that flowed down southeastward on the slope is noticed to have come close to the coast. There, the lava flowing into the ocean (ocean-entry) occurred. The shapes and locations of thermal anomaly areas are different depending on the date of images taken, it shows that the lava flows effused repeatedly with changing effusion points and flow-down paths little by little. In the meanwhile, in Fig. 3, the plume (which contains volcanic ash and so look dark) which is caused by the lava fountain and white smoke originating from vapor produced by the ocean-entry of lava (whitish tone due to the main contents of water droplets) are observed by the visual images. Furthermore, discolored water (due to the components of iron, aluminum, silica, etc. originating in the lava) caused by the ocean-entry of the lava flow are also observed (Fig. 4).
Fig. 2. Occurrences of the lava flow of Kilauea volcano in Hawaii, observed by "Shikisai" Images taken on May 5, 16, 20, 23, and 27, 2018 (brightness temperature images produced from the thermal infrared images with spatial resolution of 250 m. Temperature unit K: Kelvin = Celsius deg. C + 273.15). An enlarged image of the lower Puna district is shown on the right side.
（Author: Takayuki Kaneko, Earthquake Research Institute, The university of Tokyo, June 13, 2018)