Jim Brace-Thompson began and oversees the AFMS Badge Program for kids and has been inducted into the National Rockhound & Lapidary Hall of Fame within their Education Category.

WEIRD WORDS: TAFONI

Joshua Tree National Park in California’s Mojave Desert is a geological playground filled with odd granite formations. One consists of rounded nook-like bowls in the edges of boulders and cliffs. “What caused that?” asked my sister-in-law Mary. I assumed they were cavities carved by wind-blown sand. Fortunately, a book at the Visitor Center provided a better explanation.

D. D. Trent and Richard Hazlett’s “Joshua Tree National Park Geology” informed us that such a nook is called a “tafoni.” Just like me, geologists originally thought it resulted from wind and sand. However, there’s a new theory. Namely, these tafoni reflect a time when the California desert was much more temperate and moist and filled with soils supporting vegetation enjoyed by Ice Age animals like giant bison and ground sloths.