The Needle of ‘Iao Valley, windward Maui

15 Apr

Like the Roman god Janus who had two faces on his head, the Island of Maui also has two “faces”: the windward and leeward sides. I live on the dry leeward (or southwestern) side of Maui, a tropical coastal desert that only averages about 10-12 inches of annual rainfall.  Maui’s other “face” is its lush, green windward side. Facing eastward, it averages 100-200 inches of precipitation because of the northeasterly Trade Winds that act as the steering flow for tropical storms.

All of Maui’s rainforests are located on the windward side. ‘Iao Valley, located on the outskirts of Wailuku (the county seat), is covered with dense rainforest vegetation. (‘I-ao means “cloud supreme”; pronounced “EE-ow”) In the heart of the valley stands “The Needle” (Kūkaemoku in Hawaiian), a 1,200-foot-high erosional remnant of the volcanic rocks that formed the floor of the eruptive caldera of the West Maui Mountains. The natural amphitheater of the valley is all that remains of that volcanic structure.

The Needle in Iao Valley

The 1,200 foot high Needle. The eroded ramparts of the volcanic caldera of the West Maui Mountains loom above it.
(Click on image to see a larger version.)

During the eruptive cycles of the West Maui Mountains, rising magma within the caldera injected steam, hot water, and volcanic gasses under intense pressure upward into the floor of the caldera, forming a corrosive bubble of caustic fluids that reacted with, and altered, the minerals of the hard basaltic rocks of the caldera floor. Numerous dikes of altered silicate rock cut through the caldera-floor rocks, forming structural weaknesses within them. The altered volcanic rocks then became more susceptible to erosion by rainfall and stream flow. The Needle, the weakened and fractured remnant of the caldera floor, eventually broke away from the more durable unaltered rocks of the caldera wall, forming the distinctive rock spire.

The Needle the caldera wall (right).

The Needle (left) and the face of the caldera wall (right).
(Click on image to see a larger version.)

The following image shows how thick the rainforest vegetation in growing on the sheer faces of the spire itself and the caldera walls facing it. To get some idea of the size of The Needle, note that the Eiffel Tower is only 320 metres (1,050 ft) tall, about the same height as an 81-storey building.

The Needle: a close up shot

The Needle’s dense rainforest vegetation.
(Click on image to see a larger version.)

The cleft between The Needle and the rocks of the caldera wall is traversed by a paved walking trail and a pedestrian foot bridge (shown in the photograph below). I took this shot while standing on the trail’s iron railing visible in the bottom-left corner of the image.

The Needle and the 'Iao Valley trail

The Needle and the ‘Iao Valley trail.
(Click on image to see a larger version.)

The Needle and the surrounding ‘Iao Valley are part of ‘Iao Valley State Park. It was designated as a National Natural Landmark in 1972.

One Response to “The Needle of ‘Iao Valley, windward Maui”

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