Night shining clouds or noctilucent clouds are not so common. In Iceland they can only seen around midnight in the end of July and the earlier part of August. These are very thin blue white clouds that reach up to 80 km height, whereas usual clouds only reach up to around 10 km. This natural phenomena was first described in 1885, then only in connection with major volcanic activity. For further information see: https://en.wikipedia.org/wiki/Noctilucent_cloud
Today these clouds have become more common and are not only seen in connection with volcanic eruption. It is believed that pollution is the cause, i.d. the breakdown of methane gas in the mesosphere. The reason we see these clouds light up are the ice crystal that are generated when methane gas disintegrates.
Last night at 1 o’clock, when these photoes were taken, night shining clouds could be seen from Selfoss, lighting up the northern sky. – If we have clear skies tonight, you might be lucky enough to see these beautiful clouds in the northern sky.