Day 10

Today involved a lot of hiking and ground trothing/geologic sample taking.

After breakfast, and a brief drive, we began hiking from The Cave to the Heiau. After arriving at the Heiau, we realized that there had been a miscommunication with Dr. Becker. We were supposed to start our survey at The Cave! So we hiked back to the cave to start all over again.

First we did a little survey of the groundwater and limestone inside The Cave, checking salinity temperature, and total dissolved solids etc. After acquiring some data inside The Cave we moved onto the freshwater stream that runs just outside the entrance. There we recorded the same categories of data, and based on preliminary observation in the field the water in the stream, at the bridge, is about 350% more salty than the water inside the Cave. This is due to the flow of sea water from the ocean (wave action?) upstream. One interesting finding was the water temperature gradient in the stream at that location. The water was several degrees C warmer and much saltier near the bottom of the streambed than the surface. The inverted temperature gradient is probably caused by the denser sea water (more dissolved solids) being warmer than the freshwater and the difference in density from dissolved solids being greater than the difference in density caused by the delta temperature.

After taking our water readings (with samples) we started our Hike 2.0. During the hike we stuck to the cliff rocks as much as possible to gather our samples. In total we took eleven different rock samples from limestone through volcanic rocks. If I understand the geologic history of Kauai correctly, our samples may represent a range of about 3 million years ago to “just” a few hundred thousand years ago. Not bad for a range of a little over 3 kilometers. In total we hiked almost 6 kilometers today, so I didnt feel bad about taking a little break for a quick swim at the end of it all at Shipwreck beach.

The next stage in our project will be building a spectral library of our rock samples, collecting ocean temperature data, and investigating what spectral indexes would be useful for identifying specific types of rocks using satellite imagery.