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What are loess and collapsible soils in western Oklahoma?

Reviewed by Preston, Oklahoma foundation repair consultant ยท Updated 2026-10-14

In short: Loess is wind-deposited silt, and in Oklahoma it is mainly found on the Panhandle's high tablelands, where the Richfield soil formed in loess 3 to more than 10 feet thick 1. Loose, dry wind-laid soils are associated with collapse on wetting. That is the reverse of expansive clay, which swells when wet 4. In both cases water is the trigger, so water sources matter.

What are loess and eolian soils?

Loess is silt that wind picked up and dropped in sheets across the landscape. Eolian simply means wind-deposited, and covers sandy deposits as well as silt.

Oklahoma examples from USDA official soil descriptions:

Soil series Parent material Setting
Richfield Calcareous loess, 1 to more than 3 meters (3 to 10+ ft) thick 1 Nearly flat tablelands at 2,600 to 4,600 ft; 13 to 22 inches of rain a year; includes the Oklahoma Panhandle 1
Dalhart Loamy wind-deposited sediments 3 Sand sheets and interdunes on Southern High Plains tablelands; type location in Cimarron County; 15 to 23 inches of rain a year 3
Ulysses Loess 2 Central High Tableland; Oklahoma was removed from the series' range in 2016 2

Richfield's subsoil is a silty clay loam or silty clay with 35 to 42 percent clay and a smectitic mineral class 1, so a loess soil can also contain swelling clay in its subsoil. See the Richfield soil page for details.

How does collapse differ from swell?

A collapsible soil is a loose, low-density soil that holds its shape while dry but loses volume when water soaks in under the weight of a building. The result is settlement, often sudden and concentrated where water entered. The mechanism is described on the hydrocollapse page.

Expansive clay does the opposite: clay minerals such as montmorillonite swell substantially when wet 4, and Oklahoma's Permian clay soils owe their shrink-swell to water absorbed between the layers of 2:1 clays 6. Over 75% of Oklahoma contains bedrock units that can serve as sources for expansive soils 4, so most of the state deals with swelling clay, while collapse is a narrower concern tied to particular soils.

Expansive clay Collapsible soil
Trigger Water Water
Movement Swells (rises), then shrinks when dry Loses volume (drops)
Where it comes from in Oklahoma Clay soils weathered from bedrock, over most of the state 4 Loose wind-deposited soils; in Oklahoma, wind-deposited soils occur on the Panhandle tablelands 13

Which water sources matter?

Because wetting triggers collapse, the source of water matters: plumbing leaks, roof runoff, irrigation and poor grading. A simple supply-leak check is to read the water meter, use no water for two hours, and read it again; any change probably means a leak 5. See plumbing leaks under slab and surface drainage and grading.

How are collapsible soils repaired?

Repair options on collapsible ground are compared on the method selection matrix. They include piers taken through the loose layer to firmer support, such as steel push piers or helical piers, void and compaction grouting in some cases, and drainage control.

Free, plain-English answers. It asks a few questions and walks you to the repair that fits.

Common questions

What is loess?

Loess is silt that was carried and deposited by wind. In Oklahoma, the Richfield soil of the Panhandle tablelands formed in calcareous loess 3 to more than 10 feet thick.

Where are loess soils found in Oklahoma?

Mainly in the Oklahoma Panhandle. The Richfield series, formed in loess, is mapped there, and wind-deposited sandy soils such as the Dalhart series have their type location in Cimarron County.

What is a collapsible soil?

It is a loose, dry soil that holds its shape while dry but can lose volume when it is wetted under a load, causing sudden settlement. It is the opposite reaction to water from expansive clay, which swells.

Is the Ulysses soil mapped in Oklahoma?

No longer. The official USDA description for the Ulysses series, a loess soil, notes that Oklahoma was removed from its range in 2016.

Sources

  1. Official Series Description - RICHFIELD Series USDA Natural Resources Conservation Service
  2. Official Series Description - ULYSSES Series USDA Natural Resources Conservation Service
  3. Official Series Description - DALHART Series USDA Natural Resources Conservation Service
  4. Geologic Hazards in Oklahoma Geological Society of America (abstract by K. V. Luza, Oklahoma Geological Survey)
  5. Checking Your Water Meter for Leaks U.S. Environmental Protection Agency, WaterSense (January 2017 archive)
  6. Shrink-Swell and Other Characteristics of Five Benchmark Soils of Western Oklahoma (Technical Bulletin T-150) Oklahoma State University Agricultural Experiment Station

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