Weekly Water Photo – 18 of 52 (a picture in your mind)



I want you to provide the picture – a picture in your head – a mind picture!!

Today it is not a photo I want to show you – it is a photo I want you to conjure up in your imagination. For most people we all have memories of stuff that has happened in the past and this is all tied up with our senses.

Spring is a fantastic time of year and after this particularly long dry spell I was walking to the shops last night when it hit me:

petrichor (PET-ri-kuhr) noun

The pleasant smell that accompanies the first rain after a dry spell. Everyone has smelt it, everyone has commented on it to someone – that lovely smell after it rains.  It can be caused by any number of things.

The one we often notice in the woods, is actually caused by bacteria! Actinomycetes, a type of filamentous bacteria, grows in soil when conditions are damp and warm. When the soil dries out, the bacteria produces spores in the soil. The wetness and force of rainfall kick these tiny spores up into the air where the moisture after a rain acts as an aerosol (just like an aerosol air freshener). The moist air easily carries the spores to us so we breathe them in. These spores have a distinctive, earthy smell we often associate with rainfall. The bacteria is extremely common and can be found in areas all over the world, which accounts for the universality of this sweet “after-the-rain” smell. Since the bacteria thrives in moist soil but releases the spores once the soil dries out, the smell is most acute after a rain that follows a dry spell, although you’ll notice it to some degree after most rainstorms.

So – what is your picture of the week?

One comment

  1. Christian · May 8, 2011

    Beautiful image. As I read this post, it’s just started raining heavily after 2 weeks of hot sun. Apt.

    The fishing weather on the danish coast is illustrated by my weekly water photo: http://www.flickr.com/photos/haumovie/5709426831/

    Garfish is fun on the fly:)

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