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Document Type

Research

Keywords

catsteps, climate change, Little Ice Age, Loess Hills, terracettes

Abstract

Catsteps are the staircase-like features common on hillslopes of the Loess Hills of western Iowa. The record of artistic depictions of the Loess Hills was examined to determine when catsteps appeared. George Catlin, Karl Bodmer, and John James Audubon traveled up the Missouri River m 1832, 1833 and 1843, respectively, and between them, produced 31 works of art depicting either the Loess Hills or the loess bluffs on the Nebraska side of the river. Only three works by Bodmer of Blackbird Hill on the Nebraska side possibly show catsteps. The Assistant State Geologist, Orestes St. John, produced six sketches of the Loess Hills in 1868, half of which show well-defined catsteps. In illustrated atlases of the Loess Hills, published in 1875 and 1885, 45-55% of drawings show well-defined catsteps. The appearance of catsteps during the late 1860s may be related to the appearance of gullies during the period 1860-1900. Census data show that peak grazing of the Loess Hills was not attained until about 1900 so that climate change following the end of the Little Ice Age in the mid-nineteenth century is a more likely explanation for the appearance of catsteps and gullies. The most probable climate change is a decrease in the periodicity of precipitation cycles, which will increase the slumping tendency of loess. Such a climate change is consistent with tree rings and ostracode shell chemistry from northeastern South Dakota, tree rings from eastern Montana, and fire scars from northwestern Minnesota, but not tree rings from central and eastern Iowa.

Publication Date

July-December 2006

Journal Title

Journal of the Iowa Academy of Science

Volume

113

Issue

3-4

First Page

69

Last Page

80

Copyright

© Copyright 2008 by the Iowa Academy of Science, Inc.

Language

EN

File Format

application/pdf