Kauai Island: History, Geology, and Landscape

Kaua’i Hiking (Nā Pali Coast)

Mezmerizing and ominous is the Nā Pali Coast, the northwestern side of Kaua’i where no roads or homes exist.  The only navigable route is by foot, on the Kalalau Trail, an 11-mile journey that leads to Kalalau Beach.  The rugged Nā Pali Coast creates a spectacular scene for visitors, but the island did not always appear as it does now.

Kaua’i – The Garden Island

Kauai is fourth in size among the main Hawaiian Islands at 555 square miles of land­— it’s 33 miles long and 25 miles wide.  Its highest point is near the center of the island at Kawaikini Peak at 5,170 feet.  Second highest is Mt. Wai’ale’ale at 5,148 feet.   Mt. Wai’ale’ale is the center of a large volcanic mountain from which lava flowed down on all sides, and is the largest shield volcano in the Hawaiian Islands.  Mt. Wai’ale’ale is literally the wettest spot on earth, with some portions of the summit recorded as receiving 600 inches of rain per year.  All of this water feeds the island’s vegetation on a consistent basis, creating waterfalls, streams, verdant valleys and spectacular green and orange cliffs that have given Kaua’i its nickname of “The Garden Isle.”

Napali Coast
Severe erosion as seen on the Na Pali Coast of Kauai

Kaua’i Island Formation

The Hawaiian Island archipelago consists of 132 islands, atolls, reefs, shallow banks, shoals, and seamounts, and spans a total length of sixteen-hundred miles.  The continuous northwestward movement of the Pacific Tectonic Plate across the fixed Hawaiian Magmatic Hot Spot is responsible for the formation of the entire Hawaiian Island chain.  Incredibly, islands have been forming from this fixed hot spot for over 80 million years.

Kaua’i is the northernmost island of the eight, main Hawaiian islands, but the entire island chain extends much further: from The Big Island of Hawai’i in the west, to Midway and Kure in the east. Initially, Kaua’i was located where the Big Island of Hawai’i is today.   As you move from west to east, the islands become younger.  For example, the Big Island of Hawai’i is the youngest island in the Hawaiian Island chain, and is still quite volcanically active.  To the southeast of it lies Lo’ihi Seamount, Hawai’i’s newest submarine volcano which is completely underwater at this time.  Lo’ihi could become Hawaii’s newest island when it breaks the surface of the ocean some day.

While Kaua’i is the oldest of the main Hawaiian Islands, just exactly how old is Kaua’i?  Geologists have concluded that the island is at least 5.1 million years old, with chemical testing indicating that Kaua’i contains rocks between 5.6 to 3.8 million years old.
There has been some argument over whether Kaua’i formed from a single, major volcano or more than just one.  A 2010 study from the University of Hawai’i revealed that there were actually two major shield volcanoes responsible for the island’s formation, one on Kaua’i and one in the region between Kaua’i and Ni’ihau.  Ni’ihau is the island located west of Kaua’i, and is therefore the remnant of the first major volcano.

Once dome-shaped, Kaua’i’s physical appearance has gone through many phases over the past 5 million years.  First arising from a submarine volcano (e.g. an undersea volcanic eruption), the island formed when the eruption finally broke the surface of the ocean as a central shield volcano, followed by landslides, shield collapse, erosion, and a series of more volcanic eruptions.

There continues to be a constant state of erosion occurring on Kaua’i, and this will eventually lead to the shrinking of the island back into the ocean.  Scientists predict this may happen in 2-3 million years.

Nā Pali Coast of Kaua’i

The Nā Pali Coast of Kaua’i is an example of a shoreline that has been severly eroded by wave action.  In the winter months, it is customary for the north and northeast-facing shores to receive surf with heights of up to 40 feet. This wave action is further intensified when combined with consistent Hawaiian trade winds and rains which cut through the porous rocks like knives.  Spectacular sea arches and sea caves have formed in the cliffs as a result of the relentless pounding Hawaiian surf.  Sometimes, overhanging arches crash to the ocean below, creating sea cliffs with sheer drops.

Napali Coast
Spectacular sea arches have formed in the cliffs as a result of the pounding, Hawaiian surf.

The sea cliffs along Nā Pali Coast provide an opportunity to see what happens internally when a volcanic cone erupts.  The pressure from hot, liquid magma forms cracks in the existing hardened, lava beds.  This hot lava then flows into the cracks, and cools slowly over time.  The resulting lava dikes are the “veins of the volcanic rock.”  One could map out the dikes’ directions, to determine roughly where the center of the original volcanic cone was once located.  Dikes appear as vertical and slightly diagonal strips, and are up to several feet in width.   They are easy to spot because they run perpendicular to the layers of basalt rock in the cliff.

Napali Coast
Lava dikes appear like veins in the volcanic rock.

Plan the Kalalau Trail hike by making an advanced reservation for camping in the “Napali Coast State Wilderness Park.” Rates are $15 per person per night for Hawaii residents, and $20 per person for non-residents.  [Buy Permit]

+ 15% OFF!

Nā Pali Raft Adventure

Seize the adventure!  Your Kauai raft tour begins on our 30-foot Zodiac© rigid-hull, inflatable raft.  We take you to Kauai’s

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