Des Moines, Iowa – A rare Midwest earthquake early Tuesday is drawing increased attention across Iowa as a powerful surge of Arctic air drives temperatures sharply lower, creating conditions that could lead to frost quakes during the coldest overnight hours.
According to the U.S. Geological Survey, a 3.5 magnitude earthquake struck central Illinois shortly before 2 a.m. Tuesday, centered about 35 miles south of Springfield. The shallow quake was felt across a wide portion of Illinois, with thousands reporting shaking and loud rumbles before sunrise. While no damage was reported, seismic events of this size are uncommon in the central Midwest, making the timing notable as extreme cold tightens its grip across the region.
As the deep freeze spreads into Iowa, geologists say rapid temperature drops can trigger frost quakes, also known as cryoseisms. These occur when moisture in the ground freezes suddenly, causing soil and rock to contract and fracture. The result can be a loud boom or brief shaking that may rattle homes, outbuildings, and vehicles, often overnight or before dawn.
Central and northern Iowa, including Des Moines, Ames, Fort Dodge, Mason City, Waterloo, and rural areas with recently saturated or frozen ground, may be especially susceptible as temperatures plunge well below normal. Frost quakes are shallow and localized but can crack pavement, foundations, and underground utilities.
State emergency officials emphasize that frost quakes are not tied to fault lines and do not signal larger earthquakes. Residents are encouraged to remain alert during the coldest hours, inspect property if shaking or loud booms are noticed, and report unusual ground movement to local authorities or the USGS. With dangerous cold expected to persist through midweek, additional advisories or alerts may be issued as conditions continue to evolve.
