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!

The EarthWord: Alluvial Fan

Definition:

• Remember earlier when we covered fluvial? This word’s closely related to it. An alluvial fan happens when a fast-moving mountain stream empties out onto a relatively flat plain. All of the sediment it was carrying falls out as the water slows down.

Etymology:

• Alluvial comes from the Latin alluvius, which meant “washed against.”

Use/Significance in the Earth Science Community:

• Alluvial fans are part of the natural process of how mountains are eroded into plains. They also play an important role in spreading nutrients around.

USGS Use:

• USGS has studied alluvial fans in many places, but some of the most striking are in Death Valley National Park.

Next EarthWord: See a flock of birds fall from the sky? There’s an EarthWord for that, and it isn’t “apocalypse”…

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