This is the nest of a cicada killer wasp, Sphecius speciosus.
Harmless, solitary and Cicada-killer wasp holes are ½ half to 1-inch around with thinly scattered loose soil, usually where there is no grass. Cicada-killer burrows have a U-shaped mound of soil at the entrance. Adults emerge June/July.
Source: All the Dirt on Gardening blog
According to the Wikipedia article linked above:
this species occurs in the eastern and midwest U.S. and southwards into Mexico and Central America.
so being in Michigan, you are certainly within the region in which the insect is found.
Parenthetically, also according to the blog from above:
Crayfish holes are 1-inch wide, 2-inches high and made of mud balls.
and the texture of that hole looks more even.
Related Bio.SE question: Cicada Killer Behavior