if congress authorizes funds for the states to build highways contingent on passage of state law raising the drinking age to 21, this would be an example of which type of law?

If you mean how the great lakes formed, then  the great lakes began to form at the end of the last glacial period 14,000 years  ago, ice sheets  retreated, which led to exposing the basins they had carved into land which then filled with melt-water.