James Tiptree, Jr. was the pseudonym of Alice Sheldon and possibly something of an alter ego. Tiptree shared much of Sheldon’s early life but went on to do things that Sheldon seemed unable to do in her own name, like write stories like this.
It was not a large crater; just over a kilometer in width and lacking the usual displacement lip. Its surface was covered with a finely divided substance which dried into dust. Before the rains began it was almost perfectly flat. Only in certain lights, had anyone been there to inspect it, a small surface marking or abraded place could be detected almost exactly as the center.
Two decades after the disaster a party of short brown people appeared from the south, together with a flock of somewhat atypical sheep. The crater at this time appeared as a wide shallow basin in which the grass did not grow well, doubtless from the almost complete lack of soil microorganisms. Neither this nor the surrounding vigorous grass were found to harm the sheep. A few crude hogans went up at the southern edge and a faint path began to be traced across the crater itself, passing by the central bare spot.
One spring morning two children who had been driving sheep across the crater came screaming back to camp. A monster had burst out of the ground before them, a huge flat animal making a dreadful roar. It vanished in a flash and a shaking of the earth, leaving an evil smell. The sheep had run away.
Since this last was visibly true, some elders investigated. Finding no sign of the monster and no place in which it could hide, they settled for beating the children, who settled for making a detour around the monster-spot, and nothing more occurred for a while.
The following spring the episode was repeated. This time an older girl was present but she could add only that the monster seemed to be rushing flat out along the ground without moving at all. And there was a scraped place in the dirt. Again nothing was found; an evil-ward in a cleft stick was placed at the spot.
When the same thing happened for the third time a year later, the detour was extended and other charm-wands were added. But since no harm seemed to come of it and the brown people had seen far worse, sheep-tending resumed as before. A few more instantaneous apparitions of the monster were noted, each time in the spring.
At the end of the third decade of the new era a tall old man limped down the hills from the south, pushing his pack upon a bicycle wheel. He camped on the far side of the crater, and soon found the monster-site. He attempted to question people about it, but no one understood him, so he traded a knife for some meat. Although he was obviously feeble, something about him dissuaded them from killing him, and this proved wise because he later assisted the women to treat several sick children.
He spent much time around the place of the apparition and was nearby when it made its next appearance. This excited him very much, and he did several inexplicable but apparently harmless things, including moving his camp into the crater by the trail. He stayed on for a full year watching the site and was close by for its next manifestation. After this he spent a few days making a charmstone for the spot and then left, northward, hobbling, as he had come.
More decades passed. The crater eroded and a rain-gully became an intermittent steamlet across one edge of the basin. The brown people and their sheep were attacked by a band of grizzled men, after which the survivors went away eastward. The winters of what had been Idaho was now frost-free; aspen and eucalyptus sprouted in the moist plain. Still the crater remained treeless, visible as a flat bowl of grass, and the bare place at the center remained. The skies cleared somewhat.
After another three decades a larger band of black people with ox-drawn carts appeared and stayed for a time, but left again when they too saw the thunderclap-monster. A few other vagrants straggled by.