Aside from the famous Geysir and Strokkur, there are a series of smaller geothermal springs. The hot springs of Haukadalur have been active for almost 10,000 years. The azure blue colour of the water is from dissolved silica.
Strokkur is a smaller, but more active spouting spring, than its famous resident, Geysir. It generally reaches a height of 10 – 20 metres, but can reach up to 40 metres. Quite often, geyser activity subsides (they become ‘quiescent’), but they can be set off again by strong earthquake activity.
There are between 150 to 400 earthquakes a week in Iceland, though these are generally too small to be felt and only register on a Seismometer.
(Information obtained from the website, ‘Extreme Iceland.’)