What’s with the long downward slope on I-90 as you go northwest past Albion, WI?

It was really striking to me as we got into the home stretch of our long family car trip this summer, because just a day or two earlier we had driven through Pennsylvania and experienced a similar long stretch as we descended from the Appalachians. But I’ve never experienced this elsewhere in the Midwest, and I don’t see anything on the map to explain it.

The terrain in WI is due to glaciers (or lack thereof). I’m guessing there is a glacial ridge that you were heading down from.

Brian

Huh, okay. Is that what formed at the southernmost extent of glaciation during the Ice Age?

I don’t have time to look it up now, but it is certainly possible a terminal moraine is there https://en.wikipedia.org/wiki/Terminal_moraine

Brian

Glaciation got about as far south as Madison in that neck of the woods, so it’s certainly possible that is was a glacial feature. The U. Wisconsin Extension Program notes that the terminal moraine of the Green Bay lobe of the ice sheet is in that vicinity. There are also drumlins in the area.

There’s also the Niagara Escarpment, which doesn’t owe quite as much to the glaciers. But that’s further north and east from Albion.

I’ve looked up the topo map of the area:
https://www.topoquest.com/map.php?lat=42.89545&lon=-89.06252&datum=nad27&zoom=8&map=auto&coord=d&mode=zoomin&size=m

and note that the highway comes over a ridge and down into a creek/river valley (Saunders Creek). But instead of crossing it obliquely, where you come down, cross the river and go back up…The highway, comes down and follows parallel to the stream.

So my answer is that you come down into a river valley flood plain and drive along through the valley towards the northwest. Its a shallow valley for sure compared to mountainous areas, but it is still a drop that is long and drawn out…and flat

Interesting! Thank you. So the grade was slight but noticeable, and just kept going for a long time.