The strange booms you heard on Sunday night weren’t the stomps of Bears or Packers fans, they were likely from cryoseismic activity! Lisa Kammes from Sycamore says “My husband went to the back yard to check on [the booms]. My neighbor called police. We heard lots, until we finally fell asleep at 3am. Kelsey Brown of Pecatonica said it sounded like someone “hitting the side of the house.” In South Beloit, Bobbi Bilderback reports that her dogs started barking. And down the road from her in Rockton, Marcie Severson-Haselton said she heard three loud booms. “My son even woke up and came to our room immediately!” At my house in Southwest Rockford, it sounded like someone threw something heavy onto my roof. For me, it was more of a thud. I didn’t put two and two together until I heard about other people who heard the strange sounds.
Some of you on Facebook were correct when I asked what the strange sounds were from: a cryoseism. Because our ground is pretty dry, the warm air on Sunday allowed water to seep deep into fissures and cracks. The water flowed down into and around the rock and limestone. When the Arctic cold front came through during the day, the temperature dropped quickly. We all know that water expands as it freezes (the reason why soda cans explode when they freeze and why a milk jug of water will expand to a ball-shape if it freezes). The water in all of these cracks expanded so quickly, it created mini explosions…explosions of water and ice all over the region. These booms aren’t enough to physically shake the ground, but they are enough to startle livestock and unsuspecting people!
Cryoseisms are a fairly rare occurrence here in Northern Illinois, as the temperature drop has to be fairly quick…from above freezing to very cold, in a short amount of time. If you heard them, chime in on our Facebook page! -Eric
This post was written by Eric Sorensen on December 30, 2013