Fragipan

{
  "id": "MLC-T-ENV-011644",
  "term": "Fragipan",
  "field": "Environment",
  "definition": "1. A fragipan (modified from L. fragilis, brittle, and pan; meaning brittle pan) is an altered subsurface horizon, 15 cm or more thick, that restricts the entry of water and roots into the soil matrix. It may, but does not necessarily, underlie an argillic, cambic, albic, or spodic horizon. It is commonly within an argillic horizon, but some are within an albic horizon. The fragipan has strongly developed fragic properties. Commonly, it has a relatively low content of organic matter and a high bulk density relative to the horizons above it.\n\n2. A loamy, brittle subsurface horizon low in porosity and content of organic matter and low or moderate in clay but high in silt or very fine sand. A fragipan appears cemented and restricts roots. When dry, it is hard or very hard and has a higher bulk density than the horizon or horizons above. When moist, it tends to rupture suddenly under pressure rather than to deform slowly.",
  "subject": "Natural environments",
  "references": [
    "USDA Natural Resources Conservation Service Soil Taxonomy: A Basic System of Soil Classification for Making and Interpreting Soil Surveys (1999)",
    "EPA Mountaintop Mining Valley Fills Draft Environmental Impact Statement Glossary at http://www.epa.gov/region3/mtntop/pdf/VIII_Glossary.pdf"
  ],
  "url": "https://mlchart.com/terminology/environment/fragipan/"
}