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Geolens

Glossary

417 words used in the labs.

Find a term from the labs, understand the process behind it, and see how it appears in the landscape. Each entry connects an explanation with a real observation and a model you can explore.

Term

O horizon

A soil layer dominated by organic material such as leaf litter and decomposing plant remains. It may overlie mineral horizons in some soils but be absent in others. Its thickness depends on inputs, decomposition and disturbance.

What to look for

White beech leaf litter at Carowiry Creek, New South Wales. Organic material on the forest floor stores carbon and provides material for decomposition.

Related labs

Soil profile →
Fallen leaves and organic litter beneath white beech trees in New South Wales, Australia.
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Explore further with USGS water glossary · USGS volcano glossary · NPS glacial geology · NASA Earth facts. Photograph acknowledgements are collected on the Image credits page.