Chicago's beaches are eroding. The ground freezes in the wintertime, making it difficult to dig. Weigh a block of limestone before and after soaking it in acid. Sand is transported along Lake Michigan beach.
Streams carry sediment along with water.
Find a stream that's safe to wade in, and measure its depth in a line across the stream. Check it again after a big storm or a flood. Freezing and thawing makes potholes in roads and make rocks break into pieces. Construct a barometer from a 2 liter soda bottle, some colored water, a rubber stopper, short piece of glass tubing, and some flexible tubing. Use it to measure air pressure over an extended period of time.