Around 12:37pm Hawaii time (6:37pm Eastern) a large earthquake struck the southeast portion of the Big Island of Hawaii.
This earthquake is the largest in a sequence accompanying a major eruption of the Kilauea Volcano’s East Rift Zone that began May 3. Most of the volcano is a national park. The East Rift Zone, unfortunately, has neighborhoods on top of it, and the latest eruption is breaking out in the middle of one of them.
Scientists from the Hawaiian Volcano Observatory flew over the new eruption soon after it started and captured pictures and video of the eruption. The first thing to notice is that the area has not seen an eruption in a long time. The landscape is forested and, unfortunately, also developed. Houses are sprinkled throughout the trees in this subdivision, and much like the homes at Kalapana, these homes are now in direct danger of being destroyed by lava flows. Luckily, these lava flows are sluggish so far, so no people are in danger and the subdivision is currently being evacuated. The subdivision has over 700 building and 1700 residents. Looking at the USGS map of Kilauea, it appears that there haven’t been eruptions in this part of the East Rift zone since 1955 and most of the flows in the area date from the 1840s and 1790s.
The quake appears to have opened further rifts in the Leilani Estates neighborhood already threatened by lava flows. It is worth noting that the entire southeast of the Big Island is slowly rifting away and separating from the rest, and at some point in the geological future, will fall into the ocean. This is known as the Hilina Slump. Earthquake are part of that process. This has happened in the distant past and appears to be common with hotspot islands like the Hawaiian Islands (the Canaries and Azores too are surrounded by ancient undersea landslides). You can read an overview here at Volcano Cafe (the comments are some of the few on the net that are safe too).
This part of the Big Island was last threatened by lava flows in 2014.
Kilauea is capable of eruptions more violent than the one ongoing. In or around the year 1790, the volcano erupted violently, with pyroclastic flows not typical of Hawaiian volcanoes, killing part of an army fighting during the unification wars in the islands. The eruption was unusual enough that the Hawaiian people kept it as part of their oral histories, and the footprints of the army were left behind in the ash and rediscovered in 1919. At some point in the future, Kilauea will return to that eruptive pattern.