The Devonian Period (419.2–358.9 million years ago) jawless fish Cardipeltis has been found in Utah and Wyoming. This fossil is from Lake Michigan’s Left Coast in the Great Lakes region. Is it the jawless fish? A hunk of fossilized mud?
Along this beach in southeastern Wisconsin, Lake Michigan has been eating away at beaches at an alarming rate. Every couple weeks, waves reach farther inland, moving incredible amounts of sand, revealing more and more of what lies underneath beachfront properties. Swells also deposit millions of rocks plumbed from Lake Michigan’s depths onto beaches. Could rocks and fossils never seen in this region would suddenly be revealed?
Boosted by above-average rainfall in the spring 2017, Lake Michigan swelled to its highest water level in two decades. The rising water swallowed up mounds of beach along Wisconsin and Illinois shorelines and created an opportunity for taller, stronger waves that accelerate erosion. Water levels on all five Great Lakes—the world’s largest system of freshwater lakes—currently exceed their historical average.
Great Lakes water levels generally peak in the summer after they are nourished by runoff from melting snow and rain in spring. So, forecasts initially predicted a slight decline in lake levels this summer compared with 2016, because of mild winter temperatures and relatively little snowfall and ice cover. However, experts found themselves surprised when “the faucet turned on” over the Great Lakes region in April and May, 2017. Chicago saw 13.7 inches of precipitation during the spring, more than 4 inches above normal, according to the National Weather Service.
The sizable bump in Great lakes water levels is connected to an increase in heavy rainfall documented across the area. Springtime along Lake Michigan’s Left Coast has become about 15 percent wetter over the last century, a trend attributed to climate change.
Experts also suspect lake evaporation was stunted over the winter. Usually, ice cover dictates how much evaporation can occur, but heavy cloud cover and warmer air temperatures likely contributed to less evaporation. Peak evaporation usually happens in late fall, when arctic air meets the relatively warm surface water. But winter of 2016–17 was not that cold. Forecasts by the Army Corps of Engineers indicate Lake Michigan levels will stay above their historic average heading into the fall, a season in which powerful storms have historically punished Lake Michigan’s Left Coast.