5 May 2018
A 6.9 quake hit the Big Island of Hawaii Friday afternoon as lava fountains erupted in a housing development near Volcanoes National park. The NPS has now closed the park and the area has been evacuated. Kilauea is a shield volcano and not like Mt. St. Helens which is a strato-volcano. While a Strato-volcano can have an explosive eruption that throws ash miles into the air, shield types volcanos tend to produce large lava flows.
The big Island sits atop a “hot spot” in the mantle and volcanoes will erupt as the Pacific plate passes over this spot. The Big Island is now on top of this hot spot but Maui once was and so was Oahu. Looking at the direction of the Hawaiian Islands actually shows you the movement of the Pacific tectonic plate!
These quakes indicate that magma (Lava that has not degassed at the surface) is moving and certainly a large quake like this is not good news. When was the last quake this big in Hawaii you ask? The answers to all of those questions are in an excellent pdf from the USGS and it’s worth a read here.
The image below from the USGS. Today’s 6.9 quake was in almost the very same spot as the last quake that was stronger, a 7.1 in 1975.
The quakes around the volcano are happening at a frequency of about one per minute tonight with a mag 4 every hour or so! This certainly is worth paying attention to.
Note: We have some excellent geologists who blog here on the AGU Blogosphere and being a meteorologist, this is not my expertise. I know enough to know when to ask an expert. Check back here this weekend and I suspect some more info will be coming. Hopefully, this answers some of the basic questions.