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Hawaiian Volcanoes Field Course 2010

East Rift Zone

    It started off as a nice sunny day as we drove and parked at the  Mauna Ulu parking lot. We began our epic 12 miles death march after a round of pep talk and potty break. Less than 15 minutes into the march it started drizzling. Ka’u desert looked vast and gloomy from where we first stopped by a Kipuka. This particular Kipuka, an island of old lava filled with lush vegetation in an active flow region, was where previous volcanologists observed the massive lava flow from the Mauna Ulu eruption period of 1969-1974.  


      All decked out in raingear, we braved the strong winds and slight rain towards our next stop onto the ridge in sight. Merciless, the wind blew hard on that ridge as we held on tight to our belongings and struggled to listen and write at the same time. Here, we observed an old ‘lava lake’ surrounded by a ridge or topographic high we were on. It seems like there is so much lava flowing in the area that it formed sheet flows. On the other side of the ridge where the Kipuka hill was however, there were ropey Pahoehoe all the way around the ridge to where we came from.


    As we proceeded on in the rain, we came across a collapse feature where there was an inflation event. As the hot thick lava flowed slowly over an old flow, there was a surge in lava, inflating the edges, pushing and breaking off the thick cooled outer layer that formed with contact to the atmosphere. The broken off slabs were lifted on one side but there was not enough magma influx to break off the slabs entirely. The bottom of the slabs was still attached to the lower floor.


   Going around the same collapse, we saw that behind the broken edges, there was a deflated area lower than the inflated ‘ridge’ but higher than the floor on the other side. This is due to the lack of magma to support the structure and as it cooled and deflate, the area collapsed, breaking off from the edges of the ridge.


    The rain ceased slightly and sheltered from the wind in the channel of the lava flow, we observed the big Pahoehoe flow on both sides of the channel. Mauna Ulu is one of the craters in the chain of craters on the east rift and was formed when the rift extended eastward. The main aim of the day was to head towards another one of these craters, the Napau crater where the 1983 Pu’o eruption began. The eruptions at this vent have been rather fluid and changes back and forth from the Pu’o site and the D vent. Currently, there is a lava lake at Pu’o and the D vent supplying the lava to the ocean entry at the coast.


    As the rain and wind whipped out their fury at us in the open grounds again, we trudged towards the Makaopuhi crater in sight. The front battalion took cover behind a thick pahoehoe flow and ate abit as they waited for the rest to catch up. The magnificent crater was melancholic in the mist and the sound of the harsh wind, as if sympathetic with our cold drenched souls. On a more geological note, we saw that the Mauna Ulu lava flow went down the side of the slope of the crater and there were steam coming out of slope, evidence for some steam vents.


    The Makaopuhi crater also signified the beginning of the forest trail where we would have good cover from the wind. Gratefully hiking along the dense forest path, the sun cheered up along with our moods and gave us the bits of warmth for the day. Chunky and mossy rocks signified an old flow on which the forest flourished, with beautiful orchids and bright red berries smiling at us. We passed through the calm arches of trees linked perfectly at their crowns while the wind blew the lush green leaves at the edge of the forest. Along the path was the Old Pulu Factory where ‘the soft, reddish-brown fiber covering the coiled fronds of the tree fern (Hapuu)’ and processed here between 1851 and 1884. One could easily see over the low stonewalls, within which trees and ferns grew into it, making the stonewalls seem natural to the forest.


     The calmness of the forest was made apparent as we crossed the more exposed patches of younger lava flow. Trekking on towards the Napau crater, the overgrown low ferns were making their marks on our lower legs, making some of us regret not wearing longer pants. The echos of ‘ouch!ouch!’ died down as we approached the overview of the Napau crater. Hungry, each of us settled down for lunch quietly and quickly while admiring the views and exchanging food. With a group photo, we set out on the way, satisfied.


     More surprises came our way as the sky brightened up. There was an odd stretch of old abandoned roads half covered with vegetation and the lava flow that destroyed it. The only sounds of cars were the honking from the troop imitating cars on this wide two-lane road. Moving away from this strange place, we came into an open lava flow field where some tree trunk casts were sighted along with nice lava entrails. A scout was sent out to test the ground where a collapse was.


    With a happier and more enthusiastic group, the Pacific Ocean came into view where the Hilina Pali was. As our footsteps quicken with our mood, we staggered down the last treacherous A’a flow onto a real road where the cars were parked 10 meters away. Relieved and overjoyed at the sight of the boundless ocean, our hearts beat closer as one with the new geological knowledge gained for the day.