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This week’s Theme

This week’s theme: Featuring my home area, the Loess Hills of Western Iowa.

What are ‘the Loess Hills’ you might wonder:

The Loess Hills are a formation of wind-deposited loess soil in the westernmost parts of Iowa and Missouri, and the easternmost parts of Nebraska and Kansas, along the Missouri River.

The Loess (/ˈloʊ.əs/, /ˈlʌs/, or /ˈlɛs/) Hills are generally located between 1 and 15 miles (2 and 24 km) east of the Missouri River channel. The Loess Hills rise 200 feet (60 m) above the flat plains forming a narrow band running north–south 200 miles (320 km) along the Missouri River. These hills are the first rise in land beyond the floodplain, forming something of a “front range” for Iowa, and parts of Missouri and Nebraska adjacent to the Missouri River. The Loess land formations of Iowa extend north into South Dakota and is a feature of three state Parks in South Eastern South Dakota. Union Grove State Park, Newton Hills State Park and Blood Run State Park. A view of the thin ridges that form the “spine” of the Loess Hills

During the last Ice Age, glaciers advanced into the middle of North America, grinding underlying rock into dust-like “glacial flour.” As temperatures warmed, the glaciers retreated and vast amounts of meltwater and sediment flooded the Missouri River Valley. The sediment was deposited on the flood plain, creating huge mud flats. When meltwaters receded, these mud flats were exposed. As they dried, the fine-grained silt was picked up by strong prevailing westerly winds. Huge dust clouds were moved and redeposited over broad areas. The heavier, coarser silt was deposited close to the Missouri River flood plain, forming vast dune fields. The dune fields were eventually stabilized by grass. Due to the erosive nature of loess soil and its ability to stand in vertical columns when dry, the stabilized dunes were eroded into the corrugated, sharply dissected bluffs we see today.

The dominant features of this landscape are “peak and saddle” topography, “razor ridges” (narrow ridges, often less than 10 feet (3 m) wide, which fall off at near ninety-degree angles on either side for 60 feet (18 m) or more), and “cat-step” terraces (caused by the constant slumping and vertical shearing of the loess soil). The soil has a characteristic yellow hue and is generally broken down into several units based on the period of deposition (Loveland, Pisgah, Peoria). Loess is known locally as “sugar clay” because it can be extremely hard when dry, but when wet, loses all cohesion. The Loess Hills of Iowa are remarkable for the depth of the drift layer, often more than 90 feet (27 m) deep. The only comparable deposits of loess to such an extent are located in Shaanxi, China.

Source: https://en.wikipedia.org/wiki/Loess_Hills

Enjoy!

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