Yankin yaduwar Iowan

Yankin Yankin Yammacin Yammacin (IES) yanki ne na ƙasa wanda ya fi yawa a arewa maso gabashin Iowa kuma ya kai kudu maso gabashin Minnesota . 

 Tarihin nazarin IES 
IES ta kasance cibiyar gardama ga ma'aikatan Quaternary saboda taimakon da ke tattare da shi da sauran abubuwa.

Ma'aikata na farko sun ba da ra'ayin cewa farfajiyar ta kasance ajiyar glacial tsakanin farkon matakan Wisconsinan da Illinoian. A shekara ta 1968, Ruhe ya ba da shawarar cewa wannan yanki ya sha wahala sosai a lokacin Late Wisconsinan . 

 Tarihin yanayin ƙasa 
Yawancin yankin yana ƙarƙashin ikon kafin Illinois har zuwa, tare da shekaru sama da 0.5 Ma. Wani bakin bargo na Late Wisconsinan tsohuwar loess ya rufe a wasu wurare. Taimakon IES da kansa gabaɗaya yana lebur tare da fa'ida, daban-daban interfluves zaune a samansa. Faɗin maɓalli na elliptical ana kiransa da paha kuma an daidaita su a cikin hanyar NW-SE (arewa maso yamma zuwa kudu maso gabas) yayin da kowane paha ya keɓe gabaɗaya ko kuma nesa da juna akan IES.  Tsarin NW-SE ana danganta shi da dusar ƙanƙara mai dusar ƙanƙara ta Pleistocene -era wanda ya narke akan tebur na permafrost, wanda sannan ya lalata kuma ya haifar da madaidaicin bakin ciki a cikin ƙasa. Wannan ya biyo baya da barguna na dusar ƙanƙara da narkewar dusar ƙanƙara don mayar da gemu ko gyale na bakin ciki wanda ya haifar da faffadan fili, daidaitacce, fili mai yazara da ake kira Iowan Erosion Surface. 

 Manazarta