(CNN) — The intricate design etched into a field of barley two hours south of San Francisco was spotted Monday morning by Julie Belanger, a photographer, as she and her husband were flying over.

“What is it?” was her first thought, she told CNN affiliate KSBW.

Whatever it was, “It was beautiful, quite beautiful,” she said, adding that they came upon it by chance but that she was skeptical that the crop circle was evidence of something otherworldly.

“I believe it’s possible that aliens exist, but I don’t know if they would bother making a crop circle to give us a message,” she said.

Still, the news spread quickly. The field’s owner, Scott Anthony, had just returned from vacation to his home when he got a call from one of the employees on his 2,000-acre farm outside the tiny town of Chualar, 10 miles southeast of Salinas.

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“He said, ‘Hey, there’s a buncha stuff out in the middle of the field,’ so when I went up there I go, ‘Ohhhh, shoot!’,” the 58-year-old farmer told CNN Tuesday in a telephone interview.

What he saw was an elaborate design sculpted into one to two acres of his barley field: a crop circle — more precisely, a lot of squares and rectangles within a large circle.

“To me, it looks like a computer chip, or something like that,” said Anthony, who added that he had no idea what may have caused it. “To be that intricate in design, it kind of baffles me as to how that was done,” he said about the flattened grassland. “It didn’t look burned to me, it just looked like it was pushed over.”

Soon, the news vans showed up, followed by the curious, some of whom stood on fences to get a better view. Anthony called security agents to keep people from crossing onto his farmland, where he also grows broccoli, snap peas and lettuce.

“It’s a food-safety issue,” he said.

That hasn’t stopped the roadsides from filling with the curious, many of them self-appointed experts.

“It looks like aliens to me,” Manuel Madrid of nearby Gonzales told KSBW.

“Definitely pranksters,” said Brandon Brooks of Chualar, who added, “This is kind of a strange place to have anything out of the ordinary happen.”

The latter theory got some support from Jim Gillott, who told KSBW that he had seen 20 to 30 people with ladders in the field in the days before the design was discovered.

And Jake Gain said he too had seen evidence that humans were involved.

“Every time I drove by, I saw them either parked over there,” he said, pointing, “or people in the field just walking around, and it looked like they had little GPSes or something,” he said.

And someone identified solely as “Cannot Say” posted a 2½-minute video on YouTube that shows green flashes of light emanating from what appears to be the field before dawn on Monday. “Dude, this is a crop circle,” says one of two men in the video as they clamber from their car into the field.

The founding publisher of Skeptic magazine was unimpressed.

“It looks like a couple of kids did this,” Michael Shermer told CNN. “Short of having a video of it, it’s hard to prove that kids did it. So, in that case, we have to make a choice: what’s more likely? That aliens landed in Chualar, California, or that a couple of pranksters made it?

“We have zero evidence of aliens landing anywhere; we have lots of evidence of pranksters hoaxing.”

Such circles can be made by simply dragging a rope attached to a board over the grass, he said.

Still, he noted, such stories are attractive to many. “People seem less intrigued by pranksters than they do by aliens, so it’s a compelling story for people to think that we’re not alone.”

Farmer Anthony said he was out of town during the week before the discovery, so he saw nothing that might have tipped him off that pranksters were at work. But whoever — or whatever — caused the circle has caused him no lasting upheaval — financial or otherwise. The barley was planted between cash crops to add nutrients to the fields; he is planning to plow it — and the crop circle — back into the earth on Thursday.