Found a top Mauna Kea volcanic mountain, on Hawaii Big Island, Lake Waiau is often considered the seventh highest lake in the United States. Consisting of significant archeological and geological features, the lake is located at about 13,000 feet above sea level, and it is the only alpine lake found within the Hawaiian Island Chain.
An unusual feature, lakes are not commonly found within volcanically formed islands due soil consisting of porous lava flows, cinder or ash. Water and moisture instead, simply drain away.
Its home and namesake – Pu’u Waiau – is an approximately 65,000 year-old cinder cone near Mauna Kea’s summit. As for Lake Waiau, scientists believe it to have formed within the cone somewhere near the end of the last glacial retreat, or around 15,000 years ago.
Unique amongst Mauna Kea’s cinder cones, Pu’u Waiau is distinctively gullied and eroded, and its rare soil content comprised of rich fine-grain ash and clay.
Several theories have been proposed to explain Lake Waiau’s phenomenon; the impermeable layer that traps lake waters. One suggestion is sulfur-bearing steam passed through the cone during its eruptions, or shortly thereafter transforming its cinder and ash into fine clay minerals. Resulting in water run off, instead of seeping into the ground, this supposition also would explain the cone’s amplified erosion. A second proposition is that while Pu’u Waiau was trapped under glacial ice, volcanic eruptions occurred. When its rising magma interacted with the glacial ground or surface water, the rapidly chilled lava composition altered to form dense ash beds.
A wildly creative and popular explanation amongst travel writers is the novel idea that permafrost blocks draining water, and its melting even feeds the lake. Although the existence of limited ground permafrost as been recorded at the nearby Pu’u Wekiu, Mauna Kea’s summit cinder cone (lower right cinder cone pictured above), no permafrost has been found at Pu’u Waiau. Not to dismiss the concept outright, the United States Geological Survey (USGS) cautions it is a highly unlikely scenario due to average warm air temperatures, and the fact the lake would have melted any underlying ice.
A near circular pond, Lake Waiau is relatively small and shallow. At about 300 feet in diameter, its surface area is only 1.8 acres and at its deepest point, only about 10 feet.
A sacred cultural site to Native Hawaiians, its name in the Hawaiian language means “swirling waters,” although in actuality the lake is almost always very tranquil. In mythology, Hawaiian’s believed the lake was a bottomless portal to the spirit world.
In ancient times Hawaiian chiefs made the arduous trek to Mauna Kea’s summit for the sole purpose of throwing their firstborn son’s umbilical cord into the lake, trusting this reserved a place for the child’s afterlife as a chief.
Still used today for traditional rituals, visitors should never disturb, enter or drink water from the lake.
Throughout the years, layers of silt, clay and ash continue to accumulate in the tiny lake, adding extra impenetrability to slow the lake’s seepage of water from Pu’u Waiau. Fed merely by falling precipitation and runoff, mainly from winter storms, historically lake waters can occasionally overflow into a tiny stream, traveling by way of Pohakuloa Gulch towards the ocean. Unfortunately, in 2012 the USGS reported that Lake Waiau has undergone a rapid decrease and is shrinking in size (noted in the large photo at the beginning of this article). Although fluctuations have occurred in the past, the recent decline has been deemed severe and is believed to be from higher than average temperatures, coupled with recent Hawaii Big Island drought conditions.
Interested in visiting Lake Waiau? Learn more about hiking to Mauna Kea’s summit by visiting the Mauna Kea Visitor Information Station’s website for this challenging, but rewarding day hike.
by Sarah R. Nichols
Pictured in the foreground is Pu’u Wekiu, Mauna Kea’s summit cinder cone; behind, Pu’u Waiau and the tiny alpine Lake Waiau.