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Hawaiian Volcanoes Field Course 2010


By Erica Mitchell, Megan Young, and Jorge Perez

After our near brush with death at the 'beach' yesterday, we bandaged up, saddled up, and set out for our next day of geological adventure.  Putting aside our physical discomforts, we skipped along to the Kaumana Caves, headlamps and field notebooks in tow, our digital SLR cameras bouncing on our chests.  In the middle of a lush rainforest, the cave opened to two entrances. We bravely delved into the blackness gingerly holding our electronics, headlamps winking like eyes of the Cheshire cat.

Stop 1: Kaumana Caves N 19.69002  W 155.13051
Once we descended into the dark, cool abyss we felt like we were walking into another world.  Even though we had headlamps and flashlights, it was still easy to trip on collapsed rocks and bang our heads on low hanging ceilings.  We couldn't see the end of the tube, but we could sense fresh air blowing toward us.  This cave was once an underground river of molten magma.  It was shaped like a train tunnel, but in some places the ceiling was so low that we had to duck, and in other places it was as high as the vaulted ceiling of a church.  The texture of the ceiling was drippy.  Where drips of magma fell to the floor they were frozen solid in their tracks.  On the sides of the tube was a shiny, smooth ledge.  In some places, this smooth layer looked like it was coating the cave in chocolate.  We deduced that this layer was also once a lava flow.  It was allowed to cool extremely slowly because it was insulated by the tube walls, and this gave the bubbles inside time to coalesce and eventually come out.  In fact, this insulation is so good at keeping the magma hot that the majority of lava erupted is transported by lava tubes, not by flows on the surface of the Earth. 

Stop 2: Kipuka Pu'u Huluhulu N19.68847  W 155.46681
We crawled our way out of the cave, piled back into the vans and zoomed up between the flanks of Mauna Loa and Mauna Kea.  We stopped at a tall hill covered in native trees and surrounded by a fresh looking black lava flow.  We wondered what it would have been like to be trapped on that island while it was nearly engulfed in molten rock.  On our way up to the cone shaped hill we saw a rock wall that was engulfed almost everywhere by the unstoppable flow.  We learned that it was actually built to be a lava diversion, but it didn't work out so well.  Once we were close to the hill we could notice its cone-like shape and what it was made out of.  Most of the cone was made out of small, rough vesiculated scoria, which is a super bubbly and frothy type of basalt.  Some of the cone was layered, and the layers tilted inward, in the shape of a cone.  We also observed some large, fist-sized lumps of lava in the walls. These are known as 'cow patties,' and were formed when chunks of molten lava fell and splattered on the side of the cone.  There were also solid slabs on each side of this cone that had scratch marks, which either could have been from the slabs being pushed upwards by some force or something on the outside being pulled down. After this outcrop, we trudged up the hill with our packs to have lunch. We could feel the thinness of the air as we reached the top, thanks to the 8500 foot elevation. 

Stop 3: Mauna Loa Flow Mapping N 19.58521  W 155.44997
After our scoria cone lunch, we drove farther up the flanks of Mauna Loa.  The skinny one lane road wound its way through an extremely rough sea of A'a lava. We stopped the vans, grabbed our colored pencils, and were presented with an aerial photograph of the area. We were given the task of identifying our location and the relative ages of the numerous piled up lava flows.  We devised a strategy- first to take a few widely spaced GPS coordinates at notable features to get our bearings.  Then, we found areas where two flows contacted each other.  We recorded that flows on top were younger than flows on bottom.  Then, we colored in each distinct lava flow.  By the end of the exercise, we had brightly colored pieces of art.  This exercise is important because finding relative flow ages is the first step in determining the volcano's past flow behavior.  This information can be used to warn local residents of impending fiery destruction.