USGS EarthWord of the Week

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The unsaturated zone is the area below the surface of the ground but above the groundwater table. In other words, it’s the area that is comparatively drier than aquifers, with both water and air in the pore space between rock and soil.

EarthWords is an on-going series in which we shed some light on the complicated, often difficult-to-pronounce language of science. Think of us as your terminology tour-guides, and meet us back here every week for a new word!

A diagram showing a cross-section of the subsurface, including the unsaturated zone.
A diagram showing a cross-section of the subsurface, including the unsaturated zone. Credit: USGS

Definition:

  • The unsaturated zone is the area below the surface of the ground but above the groundwater table. In other words, it’s the area that is comparatively drier than aquifers, with both water and air in the pore space between rock and soil.

Etymology:

  • Another Latin word, this time saturare, meaning “full,” or “satisfied.”

Use/Significance in the Earth Science Community:

  • The unsaturated zone plays an important role in ecosystems as a provider of water and nutrients to plants and other organisms. It also can affect the rate of recharge for aquifers that lie below it, sometimes even filtering out undesirable substances.

USGS Use:

  • USGS studies the unsaturated zone as part of its groundwater studies, as well as for geologic information in its energy and mineral resource analysis.

Next EarthWord: Sounding somewhat like velocity, but the higher this is, the slower it moves!

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