But some of the art seems more mysterious - even ghostly. There are images of distorted humanlike figures. Others, in the Barrier Canyon style, are as tall as people, a few with enormous, hollow eyes. Triangular figures, horned beings and slithering snakes dot other styles of Southwestern rock art.
Modern viewers can only guess at the intents of the artists.
Halloween didn't exist centuries ago when early American Indians carved images into rock faces, but some of the more bizarre images may have served as ghost stories to scare children, said Desert Little Bear Gonzales, an Arizona artist who creates modern rock-art images.
"Some of them are just for fun and to scare people. This has been going on forever," said Gonzales, a member of the Pascua Yaqui Tribe. "Things that go bump in the night are not just an American idea."
Gonzales, who studies rock art as part of Arizona State University's Deer Valley Rock Art Center, said the meanings of most rock-art images have been lost over the centuries. Modern tribes may identify with certain symbols, but various groups can assign different meanings to the same symbols.
Images in American Indian rock art sometimes depicted views of positive and negative spirits, with the evil images often being more frightening, he explained.
In some cases, eerie symbols may have been intended to scare people away, he said, perhaps serving as modern "No Trespassing" signs.
Clifford Duncan, a Ute elder, doesn't go for the "marking territory" theory. He said before European contact, American Indians had no concept of private property and believed the land belonged to all.
But Duncan agrees some symbols have spiritual significance. Certain rock-art panels he has visited depict events that happened to American Indians in the past, or even creation stories.
Like most rock art, the more supernatural images are open to interpretation.
"Those may be connected more to spiritual beings or referring to certain ceremonies and how [tribe members] dressed," he said.
Deepening the rock-art mystery are questions surrounding who made some of the earliest images - the Barrier Canyon style, which features seemingly ghostly human figures in places like Horseshoe Canyon.
"I think the Barrier Canyon, as a style, is the scariest style," said Troy Scotter, president of the Utah Rock Art Research Association.
Little is known about the people who created the Barrier Canyon style of rock art, which dates back several thousand years.
Even when there may be an explanation, the symbols can remain just as mysterious.
In one instance, Scotter heard about a panel that was said to have marked a place where a monster jumped out from behind the rock to scare a group of children. The art was said to have served as a playful warning to other children.
While Scotter said he could not see how those symbols conveyed that story, it is an example of how challenging it can be to assign meaning to symbols - scary or otherwise.
Where to look for rock art in Utah
Check out these Web sites for more about rock art around Utah and places to see it:
* Utah Rock Art Research Association: http://www.utahrock art.org
* Desert Little Bear Gonzales' site: http://www.rockartcreations.com/index.html
* Deer Valley Rock Art Center: http://www.asu.edu/clas/shesc/dvrac/index.html