Seltún is a hot spring area located at the Reykjarnes country park. This park lies along the middle of the vulcanic zone, that runs the lenght of Reykjarnes peninsula. Some of the greatest volcanic activity in this zone occurs in its southern reaches, where several high-temperature areas exist, i.e. areas with temperatures of over 200°C found less than 1000m underground.
The mud pools and streams at Seltún hot springs are constanly changing. For instance, a large mud pool formed when the Queen´s hole (Drottningarhola) blew up in late 1999. The stream here is composed of various gases including hydrogen sulphide, the gas that many recognise from hot springs. Sulphur compounds in the stream make the hot water too acid for plants to grow. By the stream vents, considerable sulphur may be deposited.
Hot spring geology
Cool ground water seeps down to where it is heated up by magma or a magmatic intrusion. On the way up to the surface again, the hot water dissolves various substances in the rock. At it nears surface level the water begins to boil and releases hot spring gases, above all carbone dioxide, hydrogen and hydrogen sulphide - the source of a typical hot spring smell. Sulphur forms at stream vents as the hydrogen sulphide meets air. Where the gases rise to surface water, sulphuric acid is produced an increases water acidity. The acidic water dissolves rock, resulting in the clay that characterices mud pools and their surroundings. Besides sulphur and clay minerales, various salts - generally white or yellowish in colour - are deposited by stream vents. Gradually the sulphur reacts, with oxygen and water for gipsum.
Hot sping birds
Icelanders used to believe in hot spring bird; these were supposed to dive into a bubble of the boiling water when anybody came close. The scholars Eggert Olafsson and Bjarni Palsson attempted to find such bird while on their 18th-century research expedition, but found none and thus entered in their journal:
Few icelanders believe that these are actual birds, although some feel that they are purely imaginary, or deception due to the accidential appereances of the stream over water. Other think such birds are ghosts. Finally,a few people, most elderly, consider these birds to be the souls of dead people that take on these appereance.
To log this Earthcache, mail me the answers of following tasks:
(Answer to 1. and 2. you will find on the infoboards)
1. For the manufacture of which "thing" was the sulphur in earlier times exported?
2. Find the temperatures of the info-table which I have blackened! Which temperatur is A and which is B?
3. Describe the smell of the hot mud pools in short words!
4. How do you think, one of these Hot spring birds look like. Paint a picture and post it in your log.
5. It would be nice, if you can make a photo of you or your GPS at Seltún and post it in your log!
Please enjoy your visit at Seltún!