Robert Smithson’s Spiral Jetty turns 50 this month. This year, in January, was also the 50th anniversary of another of the artist’s earthworks, “Partially Buried Woodshed.” Both works have changed dramatically since 1970 as they’ve been transformed by nature, culture, and time — which is what Smithson, who was captivated by entropy, wanted them to do.

In January 1970, Ohio’s Kent State University authorized Smithson, then an artist in residence, to dump 20 truckloads of earth around and atop a decaying shed until its center beam cracked. Afterward, Smithson donated the piece to the university, requesting that nothing be altered or removed from the work. “But of course,” says Lisa Le Feuvre, Executive Director of the Holt/Smithson Foundation, “the moment the central beam breaks, the whole of the structure is going to gradually, gradually fall apart. And that’s what Smithson was interested in, this inevitable rise into decline.”

Just a few months later — three years before he died in a plane crash at age 35 — Smithson created the “Spiral Jetty” at Rozel Point on Utah’s Great Salt Lake. Made with 6650 tons of black basalt rock and earth, the jetty would stretch 1500 feet straight out into the lake, then curl around itself, an elegant fiddlehead of mud, salt crystals, rocks, and water. At the time, high salinity levels and colorful salt-loving microbes gave the water an otherworldly red hue. Today, drought and water diversion have caused the lake’s shore to recede past the outermost edge of “Spiral Jetty,” and lower salinity in the north arm of the lake makes for water that’s still strangely pinkish but rarely the deep red Smithson found there in 1970.

“Spiral Jetty” became almost immediately iconic after Smithson presented the work to the art world through his film and then essay of the same name, and a series of aerial photographs by artist Gianfranco Gorgoni. Smithson wasn’t interested in creating art that was picturesque, “but in his essay about ‘Spiral Jetty’,” says Hikmet Sidney Loe, author of The Spiral Jetty Encyclo, “it is about the sublime. It’s about the fear, and the awe, and the terror that can be seen within a landscape. So he’s not saying, ‘look at these beautiful vistas,’ he’s saying, ‘the water looks like meat gristle.’”

Early on, people didn’t often visit the jetty. It was perceived to be in the remote “middle of nowhere” far from the center of the art world — New York City. Also, after about two years, it was swallowed up by the lake, where it stayed mostly submerged for the better part of the next three decades.

The month after Smithson finished construction of “Spiral Jetty,” in May of 1970, “Partially Buried Woodshed” was turned into its own kind of icon when, in a tragic turn of fate, the National Guard fired on and killed four student activists at Kent State. Someone anonymously wrote “MAY 4 KENT 70” onto the Woodshed’s buckling lintel, indelibly connecting the collapsing building to the turbulent political moment.

Despite its unofficial role as a memorial and also its international art world recognition, there were many who considered it a campus eyesore. Sections of the old ruin were periodically tidied up and hauled off by groundskeepers, first after most of its left side was burned by an arsonist in 1978, and later after its center beam finally fully snapped in 1982. In 1984 the remains were quietly removed by the university. Entropy, it turns out, makes people uncomfortable.

When “Spiral Jetty” resurfaced in the early 2000s, it did so into an entirely different art historical moment, distant enough from its inception to be ripe for rediscovery, reinterpretation, and various forms of nostalgia — a sunken treasure that washed up, covered in crystals. And people wanted to go see.

“Spiral Jetty” started to take on an even larger cultural significance as it came to hold the narratives, memories, and interpretations of people who’d built their own relationships to the work, and these days it’s often seen more through the lens of the picturesque by those who visit. “‘Spiral Jetty’ is a complicated work,” says Le Feuvre. “It’s many things. And it’s the sum of the many things, and it’s also not the many things… combined.” Perhaps that’s what it is to be an icon.

Currently the jetty is surrounded by salt flats with Great Salt Lake lapping at its outer edge. At the same time, “Spiral Jetty” is also a Gorgoni aerial photo of itself in 1970 surrounded by pink and blue water. It is Smithson’s essay, his film, it is the backdrop of innumerable human moments. It is completely encrusted in white crystals, it is barely visible under the water, its black rocks sinking into the expanse of salt and time, it is growing, diminishing, endlessly documented and continually changing.