Tröllabörn meaning trolls' children is Icelandic folk name for hornitos. There are about 10 of them in this area, all 4,500 years old but you can search for more further in the lava of Leitahraun. This lava flow was produced during eruption of Leiti shield volcano, which is located east of Bláfjöll mountain range. During this eruption lava was running towards sea in both directions to Reykjavík and þorlákshöfn. Many caves and lava tunnels were created.
Hornitos are formed on lava flows, especially when they cross wet area. Contact of hot lava with water creates gas (bubbles of steam) going towards top of the flow. When hot bubbles of gas finds the way to the surface ripping out solidifying ceiling, they explode together with small drops of hot lava, which are loaded up around the hole in the crust, creating rootless hornito. Hornitos can grow and exceed 10 meters in height. The process of forming hornitos is shown below:
To log this earthcache you must reach given coordinates and look towards nearest hornito (its scheme is shown on the picture below) and answer the following questions:
1. Estimate dimensions:
- a: height of the hornito
- b: height of the inner wall
- c: thickness of the wall in shown place
- d: inner diameter of this hornito.
2. Look at the pictures below and answer in which section (A, B, C) are they located:
How do you think, what is an origin of the formation shown on picture 2 (red tongue)?
3. Your photo or a photo of a personal item from the GZ zone IS REQUIRED in log..
Send me the answers through my profile on Geocaching. You can log straight away after it. I'll contact you if something's wrong about the answers.