The limestone caves and rock shelters of Indonesia’s southern Sulawesi island maintain the oldest traces of human artwork and storytelling, relationship again greater than 40,000 years. Work adorn the partitions of at the least 300 websites within the karst hills of Maros-Pangkep, with extra nearly definitely ready to be rediscovered. However archaeologists say humanity’s oldest artwork is crumbling earlier than their very eyes.
“We’ve recorded speedy lack of hand-sized spall flakes from these historic artwork panels over a single season (lower than 5 months),” mentioned archaeologist Rustan Lebe of Makassar’s tradition heritage division.
The perpetrator is salt. As water flows by way of a limestone cave system, it carries minerals from the native bedrock, and the minerals finally find yourself within the limestone. On the limestone’s floor, these minerals oxidize right into a case-hardened rocky crust. Practically all the oldest rock artwork in Maros-Pangkep—like the oldest drawing on the planet that depicts an precise object—is painted in purple or mulberry-purple pigment on that tough outer layer. The rock is immune to most weathering, offering a sturdy canvas for humanity’s oldest art work.
However beneath the floor, bother is brewing. Flowing water deposits minerals within the void areas beneath the mineralized outer crust, and a few of these minerals crystallize into mineral salts. As these crystals type, develop, and shrink, they push in opposition to the outer layer of mineralized limestone. Ultimately, the rocky canvas the place folks first drew pictures of their world 40,000 years in the past falls aside in hand-sized flakes.
To assist perceive the extent of the issue and ensure that salt is in charge, Griffith College archaeologist Jillian Huntley and her colleagues collected flakes from the partitions and ceilings of 11 caves within the space, together with Leang Timpuseng, dwelling of the oldest hand stencil. They discovered mineral salts like halite and calcium sulfate on the again sides of flakes from three of the websites. And all 11 websites confirmed excessive ranges of sulfur, which is a key ingredient in most of the damaging salts that fear rock-art conservators.
Exfoliation is not a brand new course of, however archaeologists and web site custodians in Maros-Pangkep say they’ve watched the method pace up over the previous couple of many years. A number of the native individuals who handle and shield the rock-art websites have accomplished so for generations, they usually report “extra panel loss from exfoliation over latest many years than at another time in residing reminiscence,” wrote Huntley and her colleagues.
That is no coincidence, based on Huntley and her colleagues.
Here is how the method works: heavy monsoon rains drench Indonesia and the encompassing area from November to March, forsaking water in cave programs, flooded rice fields, and brackish aquaculture ponds alongside the coast. The water carries a load of dissolved salts and their mineral elements—issues like desk salt or halite, together with gypsum, sodium sulfate, magnesium sulfate, and calcium chloride.
When the water begins to evaporate, the salt it carried stays behind as crystals, which increase and contract together with modifications in temperature and humidity. Some geological salts, like those talked about above, can increase as much as thrice their unique dimension when heated, they usually can put a formidable quantity of strain on the encompassing rock. The result’s much like the freeze-thaw cycles that allow water ice to crack rocks and concrete.
The entire cycle is extra energetic and extra pronounced when temperatures rise and the native climate swings from extraordinarily moist to extraordinarily dry each few months. And that is exactly the situations Indonesia is experiencing because the local weather will get hotter and excessive climate occasions turn into extra frequent. Increasingly more over the previous couple of many years, extreme monsoon flooding is adopted by durations of intense drought.
Individuals wrestle, rocks crack, and a bit extra of humanity’s deepest connection to itself fades away.
“We’re in a race in opposition to time,” mentioned rock-art knowledgeable Adhi Agus Oktaviana of Indonesia’s Nationwide Analysis Heart for Archaeology (ARKENAS). “Our groups proceed to survey the realm, discovering new artworks yearly. Virtually with out exception, the work are exfoliating and in superior phases of decay.”