Hveragerdi

This geothermal town sits against the mountains in a valley bubbling and steaming with hot springs and fissures opened up by earthquakes and crustal shifting. Much of the geothermal power is harnessed for heat and electricity and just below the church is a substantial urban geothermal field. This field consists of baked earth, mud pots, and several hot springs and pools.

Springs form, disappear, and change due to tectonic and volcanic activity. Water surfaces due to fissures from magma chambers that form or shut. A spring's appearance can change due to precipitation.

Folklore tells of men reporting that they had seen two birds swimming on the boiling water of a hot spring in the geothermal zone. The birds were the size of ducks, grey-black in colour with a white ring around the eyes. When they had been swimming for a time they dived under the water, and never surfaced again, although the observers waited for some time. Hveragerdi's town logo is inspired by the story of the hot-spring birds. The bird is depicted as pale blue, against a bluish white column of steam, which also signifies a clover leaf. The bird is considered to represent the souls of the deceased.

The fumerole smells like rotting eggs due to the hydrogen sulfide, which oxidizes to yield yellow sulfur, which in turn further oxidizes to form sulfuric acid. The sulfuric acid causes nearby rocks to corrode forming acidic mud. The bacteria and archaea in the fumerole speed up these chemical processes by one million times.

This spring was formerly a fumerole that was used as a dump. After the volcano Hekla erupted, the 1947 earthquake spread this garbage over the land. This spring contains sulfur oxidizing bacteria, which are found in areas with high concentrations of hydrogen sulfide (identified by gas bubbles). The bacteria appears as grey/white stripes.

On a side note, Hekla is considered to be the devil’s home. When Icelandic children misbehave, they are told their punishment will be to go to Hekla. Hekla is still active; the last eruption took place in 2000 and lasted for three days. There are no homes or vegetation in the area; it is a barren black land. Hekla has had twenty eruptions in history.

Borehole HS08 (36-90°C, pH 9, 254m deep)

This is an alkaline hot spring with vegetation and cyanobacteria which appears as a dark green slime. Two species coexist in this spring, the Mastigocladus laminosus and the Chloroflexus. The Mastigocladus appears green in colour and thrives at 45-60°C. Chloroflexus is green but appears orange since hydrogen sulfide depending photosynthesis produces carotene.

Bull’s Eye Mudhole (97-98°C, pH 7)

Archaebacteria of genus sulfolobus thrive in this mudhole, resulting in an oily slick layer floating on the surface. These are considered to be the oldest life forms, approximately 2.5 billion years old. In the past, the mudholes were used for therapeutic purposes, much like mud baths today.

Blue Spring (30-80°C, pH 6)

This spring’s intense blue colour is a result of the presence of colloidal silica, which absorbs the sun’s red wave length and reflects the green/blue to the eye.