The Mahaulepu Coast, as Kauai’s southeastern shore is sometimes called, includes some of the island’s most intriguing geologic features. Those include several sets of lithified sand dunes, among them the limestone ramparts on the north rim of beautiful Kawailoa Bay.
Kawailoa Bay’s lithified sand dunes lie in close proximity to more recently formed dunes: the Kamala Sand Dunes on the south side of the bay. The ancient dunes were built up from sand blown by the trade winds during the high sea levels of interglacial periods. It’s the same process that’s constructed the modern dunes, which are partly vegetated. Over the eons, the lime-rich sands of the ancient dunes were cemented together to form sedimentary rock: limestone of what geologists call the Mahaulepu Formation.
Specifically, the Kawailoa Bay lithified sand dunes are an outcrop of the Mahaulepu Formation’s Paoo Member. Just a short way southwest down the seashore accessed via the Mahaulepu Heritage Trail near Shipwreck Beach, you can see other ancient-dune limestones in the form of the somewhat better-known Makawehi Lithified Cliffs. That exposure is a different unit within the Mahaulepu Formation: the Makawehi Member.
The craggy, ledged appearance of Kawailoa Bay’s lithified sand dunes contrasts sharply with the soft and inviting sands of the beach. You can get a close-up view of the limestone via a footpath running along the bayfront.
Kawailoa Bay is a lovely place to visit, and not just for the lithified sand dunes. It has a dramatic backdrop, stretching from the ocean inland to the rugged green height of Haupu Ridge. (To keep the geology lesson going a little, the basalt composing Haupu actually represents some of the oldest exposed rock on Kauai, more than five million years old.) Casuarina trees cast welcome shade.
Windsurfers take to the water at Kawailoa Bay, and it’s common to see folks surf-casting here as well. That said, this is a bit more of an off-the-beaten-path bayfront, and you’ll often enjoy plenty of elbow room.
While checking out the lithified sand dunes of Kawailoa Bay (and maybe the Makawehi Lithified Cliffs as well), you can add on another geologic field trip in the near vicinity. Not far southwest, inland of Mahaulepu Beach, the largest limestone cave in the Hawaiian Islands awaits: Makauwahi Cave. Its limestone complex includes a collapsed-roof section known as the Makauwahi Sinkhole. The cave is open for tours, and you can peer into the Sinkhole from the surface.
Geology buffs and photographers will especially enjoy checking out the lithified sand dunes of Kawailoa Bay, but just about anybody can appreciate the scenery—and the relative solitude.
Insider Tips:
-Kawailoa Bay’s waters may look tempting, but the surf here can be strong and swimming often isn’t advisable.
-Don’t know where to park? You can find parking: here.
-Consider making the trip to Kawailoa Bay for sunrise, which casts some nice light on the rock formations.