HVO reported that at about 0330 on 23 July increased earthquake activity and abrupt ground deformation around Kilauea’s upper East Rift Zone likely indicated the movement of magma in the subsurface. The Volcano Alert Level was raised to Watch (the third level on a four-level scale) and the Aviation Color Code was raised to Orange (the third color on a four-color scale) at 0406. The seismicity was centered near Pauahi Crater. During 22-23 July there were about 357 earthquakes beneath the upper East Rift Zone mainly at depths of 0-4 km. Most of the events were smaller than M 2, though 13 of the earthquakes were larger with magnitudes of M 3-3.4.

Geological Summary. Kilauea overlaps the E flank of the massive Mauna Loa shield volcano in the island of Hawaii. Eruptions are prominent in Polynesian legends; written documentation since 1820 records frequent summit and flank lava flow eruptions interspersed with periods of long-term lava lake activity at Halemaumau crater in the summit caldera until 1924. The 3 x 5 km caldera was formed in several stages about 1,500 years ago and during the 18th century; eruptions have also originated from the lengthy East and Southwest rift zones, which extend to the ocean in both directions. About 90% of the surface of the basaltic shield volcano is formed of lava flows less than about 1,100 years old; 70% of the surface is younger than 600 years. The long-term eruption from the East rift zone between 1983 and 2018 produced lava flows covering more than 100 km2, destroyed hundreds of houses, and added new coastline.

Source: US Geological Survey Hawaiian Volcano Observatory (HVO)