For nearly three decades, Robert Smithson's "Spiral Jetty" lay underwater in the Great Salt Lake. Since 1999, as drought has lowered the water level, this famous American earth sculpture — a 1,500-foot coil of black basalt — has slowly re-emerged. Now it is completely exposed; the rocks encrusted with white salt crystals are surrounded by shallow pink water in what looks like a vast snow field.

In 1970, when Smithson built the "Jetty," which is considered his masterpiece, the giant black coil contrasted starkly with the dark pink water of the lake. But time and nature have left their marks.

Thousands of people have visited this once-elusive artwork while an argument is brewing 2,000 miles away about whether to leave it as is or restore it.

"The spiral is not as dramatic as when it was first built," said Michael Govan, the director of the Dia Art Foundation in New York City, which owns the work. "The 'Jetty' is being submerged in a sea of salt."

To ensure that "Spiral Jetty" is accessible to future generations, the Dia, which exhibits and preserves art made since the 1960s, has discussed raising it by adding more rocks. The Dia is also studying whether nature will restore the contrast the "Jetty" originally had with its surroundings by dissolving some of the salt crystals when the lake's waters rise, or whether the foundation needs to do something more.

But the idea of doing anything to this artwork worries some people. And the intentions of the artist, who died in a plane crash at 35 in 1973, are not clear.

"When refurbishing earthworks, you don't want to create a Tussaud's wax sculpture," said Robert Storr, a former senior curator at the Museum of Modern Art in New York and a professor at the New York University Institute of Fine Arts. "Earthworks were not made to last forever. There is a danger when restoring them to make a more perfect thing than was originally done."

Smithson built "Spiral Jetty" at a site called Rozel Point on the northeast shore because he liked the dark pink color of the water, an effect that results primarily from bacteria and algae that grow there.

Rozel Point is about 100 miles northwest of Salt Lake City, on state-owned land accessible by a 15-mile dirt road with giant potholes that can trap small cars; four-wheel drive is recommended. Smithson's estate donated "Spiral Jetty" to the Dia in 1999 when the piece was first emerging.

"The trip to see the artwork brings people to a place they would not normally experience," said Nancy Holt, Smithson's widow and executor, who lives in New Mexico. "The 'Jetty' is a vortex that draws in everything in the landscape around it."

Smithson built the spiral out of black basalt rocks taken from the shore and arranged them to a height just above the surface of the water so people could walk on the earthwork as if on a pier.