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Out of Africa: Dust Tinted Mediterranean Soil Red
Mediterranean terra rossa.
Credit: Anna Avila

The red tint of the soil of certain Mediterranean regions, including Mallorca and Sardinia, comes from dust blown in from Africa, a new study finds.

Spanish and American researchers have conducted a mineralogical and chemical analysis to ascertain the origin of the red soil, or "terra rossa," in the Mediterranean. The results of the study reveal that mineral dust from the Sahara and Sahel region of Africa, which emit between 600 and 700 tons of dust a year, brought about the reddish soil between 12,000 and 25,000 years ago.

"The first hint of the relationship between African dust and certain soils in the region of the Mediterranean is their reddish or reddish-brown color, similar to that of African aerosol filters, caused by their clay content," said study co-author Anna Ávila, of the Centre for Ecological Research and Forestry Applications (CREAF) at the Universidad Autónoma de Barcelona.

The study, detailed in the journal Quaternary Science Reviews, found that African mineral dust additions "play an important role" in the origin of the soils (palaeosols) in the Mediterranean region , namely on the island of Mallorca. Past studies have found similar results for soils on Sardinia, "which indicates the likelihood of Africa being a common source," the researchers said.

"Terra rossa" (red soil in Italian) is located on carbonate rock (with a high content of carbonate) and is spread throughout the Iberian Peninsula, the South of France, the islands in the Mediterranean, Italy and along the coast of the Adriatic Sea, from Slovenia to Greece.