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 State Historical Society of Iowa | Copyright | Privacy

The Quaternary

Geologic Age

What Happened

Carbon 14 Dates

Holocene

Development of modern soils and stream deposits and erosion.

Today

Wisconsinan Glaciation

Wind-blown loess covers most of Iowa outside of the Des Moines Lobe.

12,500
31,000

 

The Des Moines Lobe reaches north-central Iowa and deposits its debris.

14,500
17,000

 

Early Wisconsinan glaciation is evident in northwestern Iowa under a blanket of loess.

26,000
40,000

Sangamonian Interglacial Stage

Development of a soil layer and erosion on older deposits. Evident across most of Iowa, covered by Wisconsinan tills and loess.

55,000

Illinoian Glaciation

Glacial tills deposited along the southeastern edge of Iowa.

130,000

Yarmouthian Interglacial Stage

Development of a soil layer and erosion on older deposits. Evident across most of Iowa, covered by Illinoian tills and Wisconsinan tills and loess.

300,000

Pre-Illinoian Glaciation

As many as 20 glacial advances may have crossed Iowa. Their evidence lies buried under more recent sediments and soil development. Evident across most of Iowa, covered by Illinoian and Wisconsinan tills and loess.

500,000
2,500,000

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