Rain dust

---

title: "Rain dust" type: doc version: 1 created: 2026-02-28 author: "Wikipedia contributors" status: active scope: public tags: ["precipitation", "particulates", "rain"] description: "Form of precipitation containing visible dust" topic_path: "general/precipitation" source: "https://en.wikipedia.org/wiki/Rain_dust" license: "CC BY-SA 4.0" wikipedia_page_id: 0 wikipedia_revision_id: 0

::summary Form of precipitation containing visible dust ::

::figure[src="https://upload.wikimedia.org/wikipedia/commons/b/bc/Pluie_saharienne_sur_Schlefflera_2.jpg" caption="The leaves of this [[Schefflera]] show the dust marks left by rain dust (near Paris, France)"] ::

::figure[src="https://upload.wikimedia.org/wikipedia/commons/8/80/Rain_Dust_in_Plant.jpg" caption="Air pollution often causes rain to leave stains of dust after it evaporates, in [[Monterrey, Mexico]]."] ::

Rain dust or snow dust, traditionally known as muddy rain, red rain, or coloured rain, is a variety of rain (or any other form of precipitation) which contains enough mineral dust, from soils (particularly from deserts), for the dust to be visible without using a microscope.

History

The rain dust phenomenon was studied by Italian scientist Giuseppe Maria Giovene (1753–1837), who managed to correctly explain the phenomenon as early as 1803. On 7 March 1803, rain dust fell over Southern Italy's region Apulia. At that time, people believed that the rain was caused by the explosions of Italy's volcanoes Mount Vesuvius or Etna, or that it was due to the transport of matter coming from the sea floor and raised by vapor. Giuseppe Maria Giovene related the phenomenon to the wind which occurred prior to the rain event, and he came to the conclusion that the sand had come from Africa and that it had been pushed by the wind coming from south-east.

Geography

Rain dust is common in the Western and Southern Mediterranean, where the dust supply comes from the atmospheric depressions going through the northern part of North Africa. The main sources of desert dust reach the Iberian Peninsula and the Balearic Islands in the form of dust transported by wind or rain from the Sahara, Atlas Mountains in Morocco and Central Algeria.

Mud rains are relatively frequent and had been increasing in early 1990s in the Mediterranean Basin.

It also occurs in arid desert regions of North America such as west Texas or Arizona. It occasionally happens in the grasslands as it did in Bexar County, Texas on March 18, 2008.

Dust composition

The rain dust is very alkaline.

Importance

• The particulates that rain dust carries are important for the formation of long-term soil counteracting, in large part, the effects of soil erosion. The amount of solids in rain dust have been estimated at 5.3 g m−2yr−1 (in a study made in Montseny, Catalonia) in this location the dust provides 34% of the calcium needed by the holm oak. The amount of the deposition of dust particles is highly variable depending on the year.
• Saharan dust significantly increases the pH of rain water. This may counteract the effects of acid rain.
• Radioactive fallout from the Chernobyl disaster, originally deposited by wind in the immediate aftermath of the disaster in the Sahara Desert, was carried and deposited by rain dust to Northern Greece in 2000.

Blood Rain

While rain dust can cause blood rain, also known as red rain, there are other causes, such as in the case of red rain in Kerala, which is instead caused by the presence of algae spores in the rain.

References

Bibliography

References

1. [[#elogio-storico. elogio-storico, pag. 20]]
2. [[#pioggia-rossa. pioggia-rossa]]
3. (1997). "Mineralogical composition of African dust delivered by red rains over northeastern Spain". Journal of Geophysical Research.
4. (1996). "Red dust rain within the Spanish Mediterranean area". Climatic Change.
5. Fornós, Joan J., Crespí, Damià; Fiol, Lluís. (1997). "Aspectes mineralogics i texturals de la pols procedent de les pluges de fang a les IIles Balears: la seva importancia en alguns processos geologics recents". Boll. Soc. Hist. Nat. Balears.
6. (1998). "The chemical composition of dust transported in red rains—its contribution to the biogeochemical cycle of a holm oak forest in Catalonia (Spain)". Atmospheric Environment.
7. (2001). "Coloured rain dust from Sahara Desert is still radioactive". Journal of Environmental Radioactivity.
8. (1997). "Mineralogical composition of African dust delivered by red rains over northeastern Spain". Journal of Geophysical Research: Atmospheres.
9. "European Species of Subaerial Green Alga Trentepohlia annulata (Trentepohliales, Ulvophyceae) Caused Blood Rain in Kerala, India".

::callout[type=info title="Wikipedia Source"] This article was imported from Wikipedia and is available under the Creative Commons Attribution-ShareAlike 4.0 License. Content has been adapted to SurfDoc format. Original contributors can be found on the article history page. ::