East Rift zone, upper vs lower?

[Ccat]

I have a question about the Kilauea east rift zone:  where is the dividing line between upper and lower sections of the east rift zone?

Thanks to all,

Ccat

[MyManao]

I think of the subaerial part of Kilauea’s East Rift Zone in three segments, upper, middle and lower, though I know of no firm line that would mark the boundaries between each.

The Upper East Rift is the section that is driven through on the Chain of Craters Road, and predominately features smaller craters and shorter lived events.

As the rift turns to the East, and leaves the road at about Pauahi Crater, the style of eruptions change to longer lived, and the number of craters diminish as cones and shields become the dominate features. And, the craters that are there are much larger. There are two large craters, Makaopuhi which is assumed to be a collapse feature associated with the Kane Nui o Hamo vents, and Napau which is a mile or so up rift from Puu Oo. There are no larger craters East of that point.

I have always considered this transition from craters to cones is the transition between Upper and Middle rift. Puu Oo is the largest feature in that middle section. Below Puu Oo there is a stretch that’s a bit odd to about where highway 130 crosses the rift. In that area the predominate feature is the Heiheiahulu complex of cones. The interesting, and unique, feature in that area is a large series of fractures running parallel with the rift North of Heiheiahulu.

I think of the area below Heiheiahulu, where there are but a few smaller craters, and no evidence of long, many years, lasting eruptions. as the Lower East Rift Zone. Green Mountain, in that it was a phreatic eruption, introduces another difference and as such is not as easy to draw comparisons to other events mauka. 

Although the Chain of Craters has always been referred to as the Upper, and the Puu Oo eruption in the middle, and the 2018 event in the lower, I can’t find a definitive explanation of the three sections, nor a map showing firm boundaries between each.

Another difference that might play a role in their definition is the path the magma takes to erupt in each stretch of the rift. Though that is a much larger, and more speculative discussion, it does seem as though there is some difference between the three sections on that accounts as well.

All told, I hope this helps, though stimulates more thought rather than actually provides definitive answers.

[Olohana 1790]

map of the rift zones... Kilauea and Mauna Loa
https://static.temblor.net/wp-content/up...waii-5.jpg

[Ccat]

I ask this because of the way the HVO reports on upper vs lower east rift zone activity (seismic, earthquake, lava, deformation, etc.).  I have posted this question to them but haven’t gotten an answer yet.

Ccat