Highly educational

28 07 2008

After last week’s intense office work, I was dying to get back in the field. Since my knee wasn’t cleared until Saturday, my field experiences would have to be tame. Still, that doesn’t mean they were boring! Since there are a good number of pictures, I’m going to break things up into Thursday and Friday. Tonight’s post will cover last Thursday.

My boss organized a field trip for anyone interested to Kona’s Gold Coast. 13 of us set out from HVO early Thursday to begin a day of learning in the best way possible – while standing in front of the subjects of our study! The first stop was Rainbow Falls outside of Hilo.

While the average tourist might have stopped here to marvel at the falls themselves (and the tiny rainbow you can just glimpse at their base), we were here to look at the volcanic stratigraphy. Behind the mist of the falls it’s possible to glimpse columnar basalt. Lava flows of several different ages are visible here.

The next stop was at Kaumana Cave, a well-known skylight in a massive lava tube created by the 1881 eruption of Mauna Loa. The tube is about 25 miles long, and definitely illustrates the hazards posed by lava flows. The guy at the bottom of the picture is a visiting scientist from Japan, and the guy on top of the tube is one of our preeminent seismologists.

While stopped at a kipuka for some geologic question and answer time, I spotted this plant that was reveling in the morning dew. Just thought you might like some Hawaiian foliage to brighten your day! If any of you biologically-inclined sorts know what kind of plant this is, do tell.

This is an incredibly interesting thing to geologists. It’s called a xenolith, which translates from Latin as “foreign rock.” That’s exactly what it is. This particular xenolith is dunite, a rock that is composed of coarse grains of olivine and originates in the earth’s crust. Essentially, the basalt grabbed the piece of dunite from where it formed deep below the surface and carried it upward, where it came to rest inside the flow. This particular lava flow is one of the best sources of xenoliths in the entire world. It is from Hualalai volcano, and the eruption took place in 1800. There were plenty of other xenoliths nearby ranging from clinopyroxene to gabbro and more. This is amazingly interesting for someone who is captivated by crust-eruption interactions (yeah, that would be me).

Our trip informed us in detail about Kilauea, Mauna Loa, Mauna Kea, and Hualalai. The only volcano we didn’t touch on was Kohala, the oldest one on the island. My boss is so knowledgeable on all things Hawai`i that it blows my mind. I know he was born and raised on the islands, and that he’s been working at HVO for over 20 years…but still! He’s brilliant. Here is where I ought to mention that he’s the scientist who proved that Kilauea volcano has a deep plumbing system. This is critical to our understanding of the volcano’s eruptions. This is such an amazing opportunity.

After our long day of learning, we headed down to Mauna Loa’s 1881 lava flow on the western portion of the island. The flow took 8 days to reach the coast, and reach the coast it did. It travelled over 31 miles, and this is how it looks today.

Not too shabby, is it? The grass is a pretty nasty invasive species and is resistant to fire. Eradicating it is nearly impossible, but at least it makes the pictures look good. We ended the educational portion of our trip at Anaehoomalu Bay (known as A Bay by people who don’t want to attempt THAT tongue-twister). You can just look at the water and guess what we did when we got there. I’m not going to give away all of our secrets.

Tomorrow will be pictures and talk about Friday’s gravity survey. This Thursday I’m going to the southern end of the island to collect samples from littoral cone deposits on Mauna Loa’s Southwest Rift Zone. I’m ready and waiting for the fieldwork to begin anew!

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One response

19 08 2008
KonaK

If it’s the flow next to Kiholo Bay, I think you mean the 1859 Mauna Loa flow. Nice pictures.

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