Spencer, IA (northwestiowanow.com) — Cryoseisms, also known as ‘frost quakes’ or ‘ice quakes’ may have been the reason for the reports of loud booms and banging sounds in Palo Alto County Tuesday morning.

The “frost quake” occurs when the ground is saturated with water or ice. When there is a rapid drop in temperature, that saturated ground will quickly freeze. As that water underground suddenly freezes into ice, it then expands, causing the surrounding soil and rock to crack.

The cracking is what produces the loud noises — or the “frost quake”