For reasons I am not going to go into, I have been pretty much restricted to the indoors for the better part of a month. So, with geology friends visiting (from back when I was a wee undergrad), I ran back outside!
I figured what better place to take some fellow Geos than a place on the island that is NOT basalt! I am talking about the trachyte cinder and pumice cone and associated flow named Pu'u Wa'a Wa'a (pronounced Pu'u Va'a Va'a). This amazing cone is touched on in passing in my Roadside Geology of Hawaii
(1) (pgs 109-11, 122) but is one of my favorite spots. I have seen the name translated as "many-furrowed hill" and is, I believe, a Hawai'i State forest reserve. It is open weekdays only (which is why I haven't gone as many times as I would like).
There are a few trails in the reserve (ok 2 really) but we always end up on top. But enough text right? You want pretty pictures!
But first, directions!
From Mamalahoa Hwy & Waikoloa Rd, HI
Head south on the Mamalahoa Hwy for approximately 12 miles
You will enter a small town with the Big Island Country Club and Pu'u Lani Ranch
Next you will descend down the side of the lava flow
The turn is an unmarked rd on the left at the bottom of the flow
There are two large white posts on either side of the gate
From Kailua
Take Palai Rd N and up the hill to the Mamalahoa Hwy and head north
You will continue for around 14 miles North on the Hwy
You will be able to see the road going up the lava flow
the turn is on your right before you go up the flow
There are two large white posts on either side of the gate
Also it is in
Google Maps
Here is the trail map
Starting point of the hike. Hunter Check station, with Pu'u Wa'a Wa'a visible in the distance. The first part of the hike is on an old road. Pu'u Wa'a Wa'a is approximately 105,000 years old and the volume of the cone and flow combine for an estimated 5.5 km3 and according to Moore et al., (1987) (2) this makes it the "largest volume single eruption known on the island".
Trachyte! Beautiful exposed not-basalt as we lovingly call it. I looked it up in my Volcanoes in the Sea(3) book, since there wasn't much in my roadside. While the majority of Hualalai Volcano is characterized by small amounts of differentiation, the pumice cones and trachyte flow of Pu'u Wa'a Wa'a and Pu'u Anahulu are clearly different. according to Volcanoes in the Sea it is possible that these lavas are from another magma storage area separate from the main Hualalai storage area, or they may have migrated from Kohala volcano (the northern most volcano in Hawaii Island).
I was under the impression that this was the only occurrence of trachyte on my lovely Big Island however, as I continued reading I discovered that there are in fact several small domes on Kohala, as well as Pu'u Anahulu.
The cinder done itself is mostly pumice although there are scattered tryachite obsidian blocks which make up about 5 percent of the deposit, the largest of which are around 30 cm (4).
Looking back you can see the trail, the lava flow, and below that, the beach. Near the old quarry there are two abandoned buildings and the trail turns from an old road into a more classic trail. The trachyte flow you see here is almost 300 meters thick (compared to an average thickness of 5 meters for its Hawaiian basaltic cousins (3)). The flow extends 9.5 km from the cone.
Just a bunch of geologists heading up the trail. On our right in this photo is the quarry area. This is the only known source of obsidian in Hawaii. However, it is believed that this source was not utilized by native Hawaiians, as it was only exposed when the quarry was started to mine road fill (4).
There are two "humps" on the top of the cone, and this is looking back at the northern one. See that rain cloud? 5 minutes after I took this we got hit with a downpour that followed us all the way back down! I was unable to provide a lecture on the geologic history sitting on top of Pu'u Wa'a Wa'a in the rain and I hope if you are reading this Steve that I have answered any questions you had. If not, you know how to find me!
But enough about rocks you say? What about wildlife?
There are cows, sheep and, goats OH MY! We also saw horses on the way back down but it was raining too hard for me to take my camera out.
I leave you with a photo of 5 geologists, soaking wet after getting dumped on. Is this Hawaii!? Did we get transported back to the Pacific Northwest!? Aloha and mahalo for reading!
Oh hell, I can't resist adding the goofy one too!
Peace, Love, and Rocks!
1 Hazlett, R. W., and Hyndman, D. W., Roadside Geology Of Hawaii, 1996, Montana Press Publishing Company
2 Moore et al., (1987) Hualalai Volcano: A preliminary summary of Geologic, Petrologic, and Geophysical data, In: Volcanism in Hawaii, USGS Professional Paper 1350, pages 571-585
3 Macdonald, G. A., Abbot, A. T., and Peterson F. L., Volcanoes In the Sea the geology of Hawaii, second edition, 1986, University of Hawaii Press
4 HVO website, Volcano Watch, September 4, 2004 (accessed 130528)
http://hvo.wr.usgs.gov/volcanowatch/archive/2004/04_09_02.html