Thank you for following my
geographical journey of the oldest and northernmost island in the Hawaiian chain, Kauai.
Looking at Kauai’s geomorphology through an educational perspective has
been a fun learning experience! Kauai remains as my favorite travel destination. I have a newfound appreciation
for the toporgraphy of this island. I am excited to visit in the future and apply the knowledge I
acquired throughout this semester to real life!
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| (this aerial picture of Kauai gives a great depiction in the variations between the windward and leeward sides of this island) |
As we have learned, Kauai is
volcanic in origin. It is a shield volcano and was formed
around 6 million years ago over a hotspot in the Pacific Ocean. Kauai is unique because while it is a small island, it has very diverse regions and dramatically differing landforms. Kauai has been described using such imagery as, "an island draped in emerald valleys, sharp mountain spires and jagged cliffs, aged by time and the elements."(1) It took many processes over millions of years to form Kauai's lush green tropical forests, dramatically steep coastal cliffs, meandering rivers, and cascading waterfalls.
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| (Karst towers of the Napali Coast) |
Kauai is both a coastal and
a tropical karst landscape. This
means that Kauai is in a littoral zone. Being that it is an island, it is surrounded by water as well as organic
acids caused by dissolution.
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| (Notice the tide, and waves forming just beyond the lava shelf) |
The Queen's Bath is a tide pool. It origionally was a sinkhole that was surrounded by igneous
rock. Tide pools are located in littoral zones, and during high tide can be very dangerous.
Parrot fish contribute to
bioerosion. They play an important
role in sustaining the coral reef because they feed on algae, which hampers the
growth of coral. They grind up coral with their parrot-like beak and
ingest it. After the rock is
digested, they excrete it as sand. One little fish can produce about 200 pounds
of sand per year!!
I have concluded that water
in motion will be a key agent in altering the configuration of Kauai. On March
5th 2012, the island suffered a series of flash floods and at least one large landslide.
Highways were shut down and people’s homes were damaged by the slope failure. In the next ten years mass wasting will pose a huge threat to Kauai.
Kauai’s coast has many depositional landforms. A dispositional landform is the result of deposits of sediment formed through deposition of erosion and weathered surface materials. The most obvious of these are the many famous beaches scattered along Kauai’s 113-mile shoreline. Beaches are usually made up of material deposited on a wave-cut platform. Dispositional landforms can also be a bay barrier, a tombolo, a barrier spot, all of which can be seen in the images below
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| (an aerial view of a littoral zone along the Napili Coast. Note the cliffs, terrace, surf zone, wave breakers) |
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| (A text book image of dispositional landforms) |
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| (A tomboli is a sandbar of sand built by waves that connects the island to the mainland. They are formed by wave refraction and long shore drift. This is Poi Pu Beach, a popular tourist spot in Kauai ) |
There are many
erosion landforms. Areas on the leeward side of Kauai experience wave cuts,
which can be seen below
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| (Notice the swash and backwash along the shoreline) Beaches in Kauai are composed carbonate shells from marine organisms. Kauai is surrounded by a coral reef (because of Kauai’s volcanic origin, it does not have a continental source of quartz). The reef breaks down into sand by two main factors: |
- Mechanical erosion which consists mainly of waves and currents that erode the reef
- Bioerosion which is the breaking down of the structure of the reef into sediment by various marine animals.
Parrot fish contribute to
bioerosion. They play an important
role in sustaining the coral reef because they feed on algae, which hampers the
growth of coral. They grind up coral with their parrot-like beak and
ingest it. After the rock is
digested, they excrete it as sand. One little fish can produce about 200 pounds
of sand per year!!
The future of Kauai...
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| (The Wailua River which has several tributaries) |
As we discussed in class, it
takes millions of years for new forms to be created in order to dramatically
alter a landform. The last known volcanic eruption on Kauai occurred about
400,000 years ago. Current erosion
rates depict that every 40 years; Kauai’s landscape will erode by 1 inch. This means that in 1,000 years this
island will have been eroded by 25 inches. Twentry five inches may seem insignificant, however, canyons, such as the Waimea Canyon will deepen and erode further, rivers such as the meandering Wailua River will become larger and will create more tributaries.
I have concluded that water
in motion will be a key agent in altering the configuration of Kauai. On March
5th 2012, the island suffered a series of flash floods and at least one large landslide.
Highways were shut down and people’s homes were damaged by the slope failure. In the next ten years mass wasting will pose a huge threat to Kauai.  |
| (a picture of the Na Paili Coast in the 1970s) |
While I will not see significant
geomorphology of this Island in my lifetime, I predict that due to its geographical location, topography, precipitation rates, and salt weathering the windward side of Kauai will erode at a faster rate than the other Hawaiian Islands.
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| (Coastal dissolution taken in 25 years later) |
In one million years there will be significant changes to Kauai’s coast. As I have learned, basalt flows are very
porous and, therefore, most rainfall infiltrates to the groundwater system
causing coastal dissolution.
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| (This is an example of a warning that might be posted regarding Kauai's receding coast line) |
Depositional landforms, such beaches and tombolos will change drastically. The coats will continue weathering due to salt from igneous rocks. Down cutting from fluvial processes in conjunction with Kauai's northeast trade winds will cause higher wave
energies and will erode steep valleys, which are more
likely to fail, causing the island of Kauai to become less in area, as well as unstable.
Resources:
http://www.collectionscanada.gc.ca/obj/s4/f2/dsk1/tape4/PQDD_0018/MQ57281.pdf
http://pangea.stanford.edu/~keith/91.pdf
