From temperatures in the 50s this past weekend to overnight lows in the single digits tonight, these are perfect conditions for "frost quakes."
That's when liquid water flows down into the ground around rock and limestone cracks. With abruptly freezing temperatures, the water can quickly freeze and expand. It's the same reason a soda can expands and eventually explodes if you put it in the freezer.
The water in all of these cracks expands so quickly, they create mini explosions…explosions of water and ice. They aren't enough to cause any damage, but the booms can sound deep and rumbly. Where they occur, they can easily to startle livestock, pets, and unsuspecting people.
They have been observed up to a mile from the source.
-Meteorologist Eric Sorensen