Nachusa Sand Boil 2011

One of the fun natural features at the Nachusa Grasslands is a sand boil.  Sand deposits from the Wisconsin era of the Ice Age are evident in many places at Nachusa, such as the sandstone outcroppings. 

The sand boil at Nachusa occurs at a natural spring.  It is caused when water under pressure pushes up through a bed of sand.  This sand boil is active in every season, even winter!