Hawaiian Landscape Evolution

I’ve been back in Austin for a few days now, readjusting to life in the states. I’m working on processing my rock samples for my own research before I leave again on Wednesday. And by “processing”, I mean sawing them up into small pieces. Those small pieces will then be sent off to be sliced into thin sections and mailed back to me by the time I return from Hawaii in August. Then I can look at them under the microscope!

Preparing for Hawaii has been the other task slated for the short time I am spending in Austin before my next foray into the field. This time, I will be heading to the Kohala Peninsula to meet up with my friend Brendan Murphy. Brendan studies the formation of the various landscapes we see on Earth – he is a geomorphologist. I’ll be helping him out with his Phd project for the next month. I am stoked to learn more about geomorphology and to see Hawaii for the first time!

The Kohala Peninsula provides a unique location to study landscape evolution because of the sharp contrast in climate between the east and west sides of the peninsula. The peninsula formed by flows of basalt from the (now inactive) Kohala Volcano – active from ~400,000 years ago until ~100,000 years ago. The relatively consistent rock type across the peninsula makes it a perfect natural lab to compare the various styles of erosion that scale with changes in climate across this part of the big island.

Google Earth image of the Kohala peninsula. The sharp contrast between rainforest and desert is obvious here.

The peninsula is approximately 20 kilometers wide and over that distance, yearly precipitation changes from up to 4 meters per year to less than half a meter per year. Woah! Why does this change happen from east to west? It’s called orographic lift — prevailing winds push clouds against a high point (the peninsula), clouds dump their moisture on the windward side, and finally, a “rain shadow” forms on the leeward side. You can see this nicely in the above photo, where the western side is lacking in greenery. Thanks Google Earth!

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Clouds roll over the Kohala landscape. Photo by Brendan.

Of course, with great precipitation comes great erosion and sediment transport. The landscapes not only vary across the peninsula by vegetation, but also by style of erosion. Deeply incised slot canyons and towering waterfalls dominate “the wet side”, whereas the canyons on “the dry side” are less engraved into the landscape. Plenty of photos to come in the next few weeks.

So, what are we going to do in Hawaii, besides bushwhack through the jungle with our well-sharpened machetes?

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Sharpening the tools of the trade. Photo by Brendan.

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Exploring the jungle. Photo by Brendan.

Our goal while in Hawaii is to collect the numerical data that will describe the factors that are influencing the changes taking place on the Kohala Peninsula. These include measurements of streamflow, precipitation, rock strength, sediment transport rates, erosion rates, and stream profiles. I’ll write more about the methods behind this once I’m on the Pacific.

I’ll be meeting Brendan at the airport in Kona in just two days to get started. He has been in Hawaii since earlier this week and has kept me updated with photos, as you can see here. Stay tuned because I’ll continue to post photos as we bushwhack our way through the jungles and cross the desert landscapes of the peninsula.

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An evening on the Kohala Peninsula. Photo by Brendan.

Peace.[To read more about this project, read: From the Edge of the Rain Shadow and Lasers, Drills, and Ukuleles]

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5 responses to “Hawaiian Landscape Evolution

  1. Can’t wait for the next adventure!! It looks like you will have a great time.

    Safe travels:)

    Mom/Kathy

  2. Pingback: From the Edge of the Rain Shadow | KLKgeo·

  3. Pingback: Lasers, Drills, and Ukuleles | KLKgeo·

  4. Pingback: Hunting Waterfalls on Kohala | KLKgeo·

  5. Pingback: Are your rocks better than average? | KLKgeo·

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