La Perouse Pinnacle

No longer a mystery on the horizon, I finally made it out to La Perouse, a steep pinnacle of basalt standing alone like a passing ship six miles south of Tern. La Perouse Pinnacle is the tallest monolith in the atoll, all that remains of a 13 million year old shield volcano battered and torn away by relentless trade winds and powerful swells. In fact the pinnacle was once the main lava tube that supplied the building material to this extinct island. Like a conveyor belt on a mind numbingly large scale, 70 million years of WNW movement of the Pacific Plate over a hot spot in the Earth’s mantle has produced a chain of volcanoes stretching 5,000 miles long. The Big Island of Hawai’i now sits over this hotspot at the southernmost end of the chain, spewing lava from active volcanoes - creating new land as it cools. Eventually the Big Island will drift away from this active region, cutting off the supply of magma to the volcanoes and stunting any further grow of the island. It will then take on the form of O’ahu and Kaua’i, extinct cinder cones slowly eroding away as the islands move WNW. Over millions of years as erosion accelerates the island will shrink in diameter. As the area of exposed island decreases, coral that once fringed its shores will create a rim of reef around a shallow lagoon, known as an atoll, formed by millions of tiny coral polyps that build calcium carbonate structures to keep them close to the sunlit surface waters; as has happened with French Frigate Shoals and the 30 million year old Kure Atoll. So long as the coral growth matches or exceeds the islands rate of submergence, the atoll will remain at the surface. Conditions change as the conveyor belt drives forward; drifting the atoll into latitudes too cold to support coral growth. Without the coral the atoll dies, and the entire structure will finally sink below the waves. The story, however, doesn’t end there as this submerged island will become part of the Emperor Seamounts; important features in the seafloor that extent all the way to the Aleutians, known to support a diversity of marine life.

French Frigate Shoals is in one of these transitional stages, where a small fragment of the old island (La Perouse) stubbornly holds onto existence as the atoll marches north to fulfill its destiny. This unique structure in the middle of the Pacific provides a critical habitat for seabirds that prefer to nest on high relief substrate. Brown Boobies, Blue-grey Noddies, and possibly White-tailed Tropicbirds for instance all   prefer the jagged weathered rocks as a perch upon which to lay an egg. These three species are only occasionally seen investigating Tern, but without steep cliffs suitable for nesting they are merely visitors to our island home. Probably for the best, this island is crowded enough as it is.

We snorkeled the pinnacle on our visit, one of the best spots thus far, possibly rivaling the aptly named Taquito Reef. The water is deep around La Perouse and lacking in sand suitable to anchor in. To avoid damaging the reef, we carefully maneuvered the anchor chain over a patch of sand, and I swam down to set it clear of the delicate coral heads. The clarity of the water made the bottom appear deceptively closer than it was. It looked roughly 35 ft, but in reality it was likely about 50 ft. My first attempt to make the dive failed, I ran out of air 10 ft short of the bottom; this doesn’t happen often for me, another indicator of the depth. Back at the surface I was able to replenish enough oxygen in my system to make the second dive. Reaching the bottom I managed to dig the anchor barbs into the sand without entangling myself in the chain. Looking up at the surface from the deep watery world below is one of my favorite sights; I like to imagine what it would be like to live in such an environment. The depth of the reef made the snorkeling rather exhausting, especially since we were still recovering from Thanksgiving dinner, but the multitude of caves to swim through and huge satellite dish-sized shelf coral made the effort worthwhile. The shark factor felt high here, and I was constantly watching over my shoulder for any strange silhouettes. It’s rumored there exists a long tunnel that cuts through the width of the pinnacle which people have swam through, full of sharks of varying shapes and sizing. Our grapes were not feeling large enough to attempt such a swim on this day.