Nebraskans have experienced no major earthquakes but have suffered occasional seismic shocks and tremors. The state does have fault lines or cracks, generally far underground, caused by natural pressure and possibly affected by man. In late July 1902 northeastern Nebraska and southeastern South Dakota were the centers of a mild quake, reported in the July 29, 1902, morning issue of the Omaha World-Herald. According to the World-Herald, on microfilm at the Nebraska State Historical Society, the first signs occurred shortly after noon on July 28:
"So far as has been reported no damage to persons, and still less to property occurred, but several thousands of people for a few seconds thought their time was about to come, and at some points they scurried helter skelter to what they thought might be points of safety in case Mother Earth should conclude to open her mouth and swallow up the population."
Yankton, South Dakota, was the first site to report the mild quake. Subsequent reports of shocks were received from the Nebraska towns of Battle Creek, Tilden, Petersburg, Elgin, Oakdale, Norfolk, Plainview, Pierce, and Creighton. Tremors which seemed to move from west to east were also felt at the Santee Agency.
"The 'shock,' or quivering of the earth's surface, continued for from twelve to fifteen seconds, one shock only being felt at the largest number of places reporting, although one or two towns reported a double shock and one town asseverates that three occurred within its precincts. The shocks were accompanied by a ghoulish rumbling noise that was terrifying to those who heard it.
"Further than the rattling of dishes, the cracking of some few inches of plaster and the breaking of a few window panes, the earthquake's visit was remarkable only for its occurrence in this interior portion of the country. Some people in the towns which felt the shocks ascribe it to another eruption of Mount Iona on the Santee Agency, but whether or not Nebraska's volcano has become active, was unknown last night, owing to its distance from any means of communication."
"Mount Iona [Ionia]," a Missouri River bluff northeast of Newcastle in Dixon County, had been known since the days of Lewis and Clark for suspected volcanic activity. However, it was apparently unconnected with the 1902 seismic disturbances in Nebraska and South Dakota. An 1878 flood had previously destroyed part of the site and the nearby town of Ionia for which it was named. "Volcano" tales gradually disappeared after the Ionia post office was discontinued in 1907.