Aloha Kauai!

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!

(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. 

(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.   

(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.          

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 

  

(an aerial view of a littoral zone along the Napili Coast.  Note the cliffs, terrace, surf zone, wave breakers) 

(A text book image of dispositional landforms)

(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

(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...

(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 5^th 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.      

(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.  

(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:

(1) Kauai's leading travel sight

http://www.collectionscanada.gc.ca/obj/s4/f2/dsk1/tape4/PQDD_0018/MQ57281.pdf

http://pangea.stanford.edu/~keith/91.pdf

http://www.hawaii-guide.com/kauai/region/west-kauai

http://clasfaculty.ucdenver.edu/callen/1202/Landscapes/KarCoast/KarCoast.html

http://www.state.hi.us/dlnr/pdf/wailuariver.pdf

Kauai's nickname is The Garden Island.  This is because of its lush vegetation due to its geographical location and weather patterns - not because it’s an island composed of passionate gardeners!! :)

                                 (The major regions of Kauai are defined by their
                                   location on the island relative to the prevailing trade winds)

Although Kauai’s climate is tropical, it consists of many microclimates, including arid areas, rainforests, temperate and tundra climates.  Due to it's differing elevations, pressure variations, rainfall, wind and humidity; temperatures are not as extreme as you would find in a true tropical environment, so many people regard Kauai as a subtropical region.

  

Trade winds blow across Kauai from the northeast. This means that the north and east sides of Kauai are on the windward side of the island.  These sides receive the most rain.  The south and west sides of the island are on the leeward side of the island, which receive less rain - rain has already fallen on the windward side.

(A satellite image of the islands. Notice the pattern of the clouds, as well as the vegetation primarily on the northeast sides of the islands because they face the tradewinds, which bring humidity) 

 

(an example of precipitation on the leeward side of a mountain)

Trade winds in combination with Kauai’s geographic location create Kauai’s temperature.  Kauai has two seasons, summer- from may to October and winter - from September to April.  Temperatures range between 85 and 69 degrees depending where you are on the island.  Coastline temperatures average around 72 degrees in the winter months.  During spring and summer the average is around 82 degrees. 

(Annual precipitation rates for Kauai)

These two graphs show Kauai's difference in precipitation rates within the regions of the island:

(Poipu, Kauai receives much less rain throughout the year than Princeville, which is on the leeward side) 

As you can see, some areas receive much less rain than others.  Precipitation is common throughout the island, however, the vast majority of rain showers are brief.  Even heavy showers in the west and north are unique because thunder and lightening are rare.  

 ("Anuenue" is Hawaiian for rainbow.  Note: The outer rainbow is the reverse of the more vividly colored inner one.)

Rainbows occur frequently all over Kauai.  Droplets of precipitation act like prisms.  In white light the colors bend and spread, causing these beautiful sights.  

*(technically there's a region in India which averages a few
more inches of rain per, however, Mount Waialeale
wins because it's precipitation rates are more consistent) 

Mount Waiʻaleʻale (Hawaiian for “over flowing water”) is known as the wettest spot on earth, averaging 450 inches of rain yearly.  It is Kauai’s second highest peak with an elevation of 5,148 feet.  It is located in the center of Kauai.  It has had a huge impact on many formations throughout the island.

Why does Mount Waiʻaleʻale receive sooo much rain? 

Kauai is positioned at the top of the main island chain.  It is conical in shape, which exposes all sides of  Mount Waiʻaleʻale to trade winds and their moisture.  When moist air rises and flows over a mountain, on the windward side it is called orographic rainfall.  

(A diagram of the orographic rainfall process)

(Adiabatic cooling)
 Note: on the Wind ward side, cumulus clouds usually form above because of the tradewinds.  

As air is heated it expands and becomes less dense.  Because it is lighter, it rises above the cooler air.  As it raises it continues to expand because there is less pressure higher in the atmosphere. This process is called adiabatic cooling and is common among elevated landforms.  The result of adiabatic cooling is precipitation.  In addition, Mount Waiʻaleʻale is below the trade wind inversion layer of 6,000 feet.  This means that clouds produced by trade winds can’t rise, there for they get stuck in one spot, hence the large average amount of rain in this particular area. 

Below Mount Waiʻaleʻale is an extinct caldera.  It is now a plateau, called the Alakai Swamp.  It is the world's highest rainforest and swampland (4,000 to 4,500 feet above the Pacific) and was formed by excess water drainage from Mount Waiʻaleʻale.  Alakai Swamp is a Montane Forest, meaning it has persistent precipitation and low-cloud cover, which retains moisture.  Because of its elevation it is considered to be one of the most unique 'swamps' in the world.    

External links:

Data Base for Hawaii

Hydrology.php

Kauai

http://www.soest.hawaii.edu/coasts/publications/hawaiiCoastline/kauai.html

Very diverse landscapes, including tall cliffs, lush forested
 valleys and plummeting waterfalls, which all have been
created as a result of several types of weathering and erosion. 

North Kauai reveals many dramatic aspects of weathering, surface hydrology, and erosion.  The  Nā Pali Coast's 17-mile coastline took millions of years to form.   One aspect about the Nā Pali Coast, which I find interesting is that due to it's geographical location, rugged landforms and climate, it is considered one of the least accessible  coasts in the world.

Kauai's climate and annual precipitation will be discussed in my next post, but I think it is important to mention that rainfall has a profound effect on weathering.   This area receives an average of 100 inches of rain per year, which affects the hydraulic properties of sedimentary rocks, especially within ash. 

The Nā Pali Coast has been featured in many movies including,  Jurassic Park and King Kong. 

"Na Pali" means "The Cliffs" in Hawaiia

As we know now, Kauai’s origin is volcanic. The  Nā Pali Coast’s cliffs are composed of basaltic lava flows.  The steep 4,000 foot cliffs that make up this coast were formed as the result of a huge landslide millions of years ago.  The landslide was created by a change, or  shift and forced part of the land to slip down into the ocean.  

Chemical weathering, salt weathering, and erosion have continued to sculpt and form this area making the  Nā Pali Coast the second fastest eroding location in the world.

(Strong wave action along the coast)
Note the crossbedding layers of Basalt and how its color and stratigraphy have changed due to oxidation

( Vertical slopes, with knife-edged divides and steep chutes formed by landslides, water runoff and other forms of weathering )

(Perfect example of oceanic waves breaking down a weak zone
in a rock and forming a sea cave)

The sea caves along the Nā Pali Coast are an unforgettable sight. Sea caves originate in the side of a costal cliff along a weak zone, known as a fault or crack.  The Nā Pali Coast’s sea caves are formed by a dike, which is when a well-eroded rock is found within a stonger, larger rock.  Due to wave action, the weak area in the rock begins to erode and caves are able to form.

(View of a sea cave along the Nā Pali Coast by boat)
Notice the cracks and fischers as well as the calcite, deposited
by water percolating through the permeable bassalt rock

(An areal view of a sea cave along the Nā Pali Coast)
Notice the salt crystal growth in the ridges of the rocks as well as the areas where the soil was been oxidized 

The Nā Pali Coast's weathering and erosion is not all caused by organic and environmental changes.  It was discovered recently that hikers and campers, as well as feral animals, such as pigs and goats created unnatural erosion process and were damaging the natural ecosystem of this unique area.   This was creating more rockfalls, mudslides and reef siltation.  Currently, efforts are being made to slow down this unnatural process.  

External links: 

Coastal Geology

Coastal Weathering - Kauai

http://pubs.usgs.gov/ha/ha730/ch_n/N-HItext1.html

(A satellite view of  Kauai)

The island of Kauai today is the result of many natural processes, which resulted in the creation of the beautiful landform that both natives and tourists admire. 

We can attribute Kauai’s unique and diverse land formations to its volcanic origin.  Kauai was formed around 6 million years ago by tectonic plates moving over a stationary hotspot in the Earth’s mantle.  A hotspot is an area of hot magma located under the Earth's surface.  It creates stationary heat and energy, known as mantle plumes.  This causes seamounts, which over millions of years rise above the surface and form an island.

(Depicting the hot spot theory)

One characteristic of hotspots is that they produce fluid basaltic lava flows, which are extrusive, meaning the lava is thin and runs away from the vent forming a large land mass with gently sloping sides. This process created the shield volcano, which is Kauai. 

The crystallization and cooling of basaltic lava around the  lava channels can be referred to as pāhoehoe flows.  Active low-viscosity lava flow forms a roof  above the still moving stream of lava.  Some lava tubes, like Kauai’s Spouting Horn, form blow holes.  As depicted below, the pressure from the waves in combination with an influx of air creates an eruption of water through the tube and out a hole.  

Rainbows often form in the incandescent spray of the lava tube at sunset.  This is a magnificent sight!  It is easy to understand why early Hawaiians created meaningful legends about this marvelous natural wonder.

                                              

When water is forced into the lava tube by the surf, it erupts into the air creating the hissing noise you hear.  People think Spouting Horn sounds and looks similar to a whale’s spout, hence its name.  When the tide is high, these erruptions can shoot as high as 50 feet. 

(Waimea Canyon)

Waimea Canyon, another renowned geologic formation in Kauai is known as the Grand Canyon of the Pacific.  This canyon is 1 mile wide, 10 miles long and an estimated 3,500-feet deep.  The translation of Waimea means “reddish in color.”  This name is very appropriate because the first thing one notices about the canyon is the rich red erosions covering the canyon’s walls.  The erosions which are exposed basalt have been weathered from their original black color to the red we see today.  The history Waimea’s formation is unique because it was created both by the steady process of rainwater flowing down from Mt. Wai’ale’ale, as well as by the catastrophic collapse of the volcano, Olokele, which created Kauai.

While Olokele, was still erupting, a portion of the island collapsed.  This collapse formed deep indentations in the land, which then filled with lava flows and became Waimea Canyon.  

The canyon is divided by a fault.  As a result, one side of the canyon is actually lower than the other.  The differences in the altitude of the fault line’s division have resulted in unique and different forms on both sides. The cliffs on the west side of the canyon are made up of remnants from thin lava flows. The oposite side of the canyon has walls, which are built from thick lava flows that formed pools in the depression.  

(Notice the stratigraphy and erosion along the canyon's walls)

               

Sources 

Earth Observatory.nasa.gov

Volcanoes.pdf

Lava Tubes

Geology of Hawaii

Aloha fellow bloggers and readers! 

This semester I am going to take you on an in depth geographical exploration of my favorite Hawaiian island, Kauai.  Kauai has varying climatic zones and diverse geological formations.  The origins of these sights sparked my interest prior to my first visit to this island.  

(Mt. Waialeale)

The annual high level of rainfall creates lush tropical plant life.  This is why Kauai is nicknamed the “Garden Isle.”  In fact, Mt. Waialeale receives an average of 460 inches of rainfall a year.  As a result this area is classified as one of the "wettest" places on the Earth, which I find truly fascinating.  I am excited to delve into the different geographical and ecological aspects of this island from its unique coral reefs to its highest mountain peaks.  Bring your bathing suit, sunscreen, hiking shoes and join me in an adventure of a lifetime!   

                                               (Spouting Horn, a natural lava tube aka a blow hole) 

(The Napali Coast) 

(Waimea Canyon, also known as the Grand Canyon of the Pacific)