One of my favorite scent memories is the wet red mud in Nairobi. I've always thought that the earth there, right after it rains, smells good enough to eat. Though I've never eaten it, last year when I was doing some research, I chatted with a guy in Georgia who carries white clay in his store. He sells it in two-pound bags to people who crave the flavor or swear by the health benefits. He told me that despite marketing it as a novelty, he'd sent the soil as far as Alaska to be eaten.
Here's a bit from an old Time magazine piece on American mud-eating, published in 1942:
Many a homesick or sardonic Northern Negro, writing to Southern friends, says "Ship me a bag of good dirt to eat." Sometimes he means it. Even in the Yazoo-Mississippi Delta, Negroes and whites send requests to their upcountry friends for a bit of red clay, declaring that black Delta soil is "right bad eating." In certain parts of Mississippi, poor whites will walk miles for a spoonful of dirt from a favorite bank of clay, because it "tastes sour, like a lemon." In other sections of the South, some top their meals with a savory tablespoon of dirt, believing that it is "good for them," despite its constipating effects.
There's something about missing a place so dearly that you actually want to consume its earth. It seems like the most perfect expression of homesickness. By the way, The Oxford American has a really wonderful piece about the Southern tradition of geophagy (the official term for dirt-eating).