On Hawaii Island, the Kau Desert on the southwest side of Kilauea Volcano is a dry, desolate landscape. Life is hindered by the frequency of acid rain, and layers of ash cover the vast, moonlike environment from centuries of eruptions.

Among the hardened lava, and dusted with sand, is a violent reminder of the volcano’s unpredictability: 1,773 human footprints fossilized in the ash, representing at least 441 men, women and children. Many of these footprints are believed to have been left by a war party that was retreating and got caught in a 1790 eruption known as Keonehelelei.

Translated, Keonehelelei means “the falling sands,” describing the ash that rained down across the Kau Desert — a huge spectacle that was reportedly seen for miles.

“The ash layers and the footprints are really fragile,” Summer Roper, acting cultural resource manager of Hawaii Volcanoes National Park, told SFGATE. “It’s pretty amazing they’ve lasted this long for hundreds of years.” Although it was typical for Hawaiians to wear ti leaf sandals during the time, a lot of the footprints are noticeably barefoot with clearly defined toe prints.

The footprints were formed when ash from an eruption traveled high into the air, intermingling with moisture. This created a permeable, wet and soft claylike substance when it fell back down to the desert floor. “People would walk through it,” said Roper. “Then when it dried out, it hardened, and that’s how the footprints would be preserved.”

The fossilized footprints were first recorded in 1919 by geologist Ruy Finch of the Hawaiian Volcano Observatory. It was Thomas Jaggar, the volcanologist and founder of the Hawaiian Volcano Observatory, who first tied the well-known tragedy of the war party and the footprints together.

As the story goes, in the late 18th century, Hawaiian Chief Keoua fought against his cousin Kamehameha, the warrior who would later unite all of the Hawaiian Islands under his rule. It was a brutal battle between armies with no clear winner.

As they retreated home to the district of Kau, Keoua took his warring party, who were also accompanied by their families, on a trail over Kilauea Volcano. The volcano showed signs of unrest, causing numerous earthquakes, so they stayed at its caldera overnight, waiting for it to calm.

After a few nights, Keoua eventually split his army into three groups, and they marched across the Kau Desert at different intervals. Most of the first and third groups made it safely; however, the entirety of the second group died, caught in an explosion of gas and steam.

It’s not clear how many of Keoua’s army perished. Reports range from as few as 80 to as many as 5,405 people.

It’s also unknown where their bodies went. There is no evidence of a deceased army lying among the footprints. One theory suggests their bodies were “thrown into Kilauea.” 

Analyzing the prints, Roper said it also doesn’t appear that anybody was running scared. “I think people were just cruising through,” Roper said. “Walking through the ash is soft, so in comparison to the pahoehoe [hard lava], I would see why people would, like, choose to walk through the ash if they don’t have shoes on.”

The story of the fallen army is the primary interpretation of the footprints section at Hawaii Volcanoes National Park. However, more research has unveiled another.

For one, the footprints are not the only historical features in the area. In 2003, archaeologists recorded 55 historic Hawaiian sites with as many as 516 structures and features, such as temporary shelters, trails, petroglyphs and stone quarry areas. 

The archaeological survey also found that the footprints are headed in different directions. Some of the footprints were discovered to be separated by different ash layers, and therefore created during different time periods.

“After the archaeological surveys and additional studies, now it’s thought that it’s tied to the warriors as well as to other people,” said Roper. It paints a broader picture of how early Hawaiians used the area as part of a trail system and as a place to gather stone tools. 

“They still think it’s tied to [Keoua’s army], but not just that event,” said Roper.

Editor’s note: SFGATE recognizes the importance of diacritical marks in the Hawaiian language. We are unable to use them due to the limitations of our publishing platform.