Have you ever been home in the middle of winter, and all of a sudden heard a loud boom or bang? (sound effect of a frost quake) Well, it could have been a frost quake! Frost quakes or cryoseisms are fairly rare, and only happen during cold weather. While they are more common in colder climates, they can also happen in warmer areas experiencing a freeze. Frost quakes happen when the ground is soaked by water from a heavy rainfall or melting snow, and this water seeps deep into the ground. A sudden drop in temperature then causes this underground water to start to freeze, and when water freezes, it expands. In order to expand, the freezing water needs space; and when it’s used up the space in the soil, it starts pushing on the ground around it. The freezing water pushes, and pressure builds, until it’s too much for the soils and rock around it, and they break apart with a loud popping or banging sound. Frost quakes often happen between midnight and the early morning as that’s the coldest time of day. They also need there to be very little or no snow cover for this deep underground freeze to occur as snow is a good insulator, and can keep the ground from getting cold enough. Frost quakes last for just a second, are generally harmless and don’t leave any signs they were there, except for those who were disturbed while trying to sleep.