Gullfoss

The waterfall falls over layers of rock.

Most layers are stuck together tightly. One layer is loose gravel. The water washes the gravel away, so the waterfall keeps digging into the rock.

Gullfoss falls over layers of rock that formed during a warm spell in the Ice Age. Rock called dolerite sits on top, and below it are layers of sediment: pebbly rock, mudstone and gravel. The gravel holds loose pockets that the water washes out easily. That is the main reason the waterfall digs back so fast.

Scientists have two ideas about how the canyon formed. One is that a giant flood from the edge of a glacier carved it at the end of the Ice Age. The other is that the river slowly cut it, bit by bit, after the ice began to melt. The Environment Agency of Iceland says the second idea is thought to be more likely.

The Environment Agency of Iceland describes dolerite layers in the falls' ridges with a sediment layer almost 10 m thick between them, of conglomerate, mudstone and gravel. All but the gravel are well bonded; the gravel is 8 m thick in the falls and 40 m at the canyon front, with loose lenses the water washes out, the main cause of the waterfall's rapid excavation.

Two theories explain the canyon: a great glacial outburst flood at the end of the Ice Age, or steady cutting by Hvítá since the glacier began to melt; the agency's web page calls the second more plausible. Its management plan says the river probably began to flow here about 10,000 years ago and that the canyon formed through both outburst floods and the river's steady flow; at Fremstaver, north of Gullfoss, end-of-Ice-Age flood flows have been calculated at up to 400,000 m³/s.

Long ago, a woman named Sigríður lived on a farm near the falls.

She and her sisters showed visitors the way to Gullfoss. They even made the first path down to the waterfall. Later she worked very hard to protect Gullfoss.

Sigríður Tómasdóttir was born in 1871 on Brattholt, a farm near Gullfoss. She and her sisters often guided visitors to the falls and built the first path down to the waterfall.

Around 1900 people began trying to control Iceland's waterfalls to make electricity. In 1907 an Englishman offered to buy Gullfoss. Sigríður's father, Tómas, refused, saying "I will not sell my friend." Later the rights to the falls were rented to foreign businesses. Sigríður traveled over mountain roads and waded across rivers to meet officials and fight the deal. In the end the businesses lost interest, and in 1928 the agreement ended.

The Environment Agency of Iceland tells the story. In 1907 an Englishman offered 50,000 krónur for Gullfoss, fifty times Brattholt's fire insurance value; Tómas of Brattholt answered, "I will not sell my friend." Gullfoss later came under a rental agreement with men representing foreign parties, and his daughter Sigríður (1871–1957) tried to have the deal set aside, traveling to officials in Reykjavík in every season; the court ruled against the family.

The foreign parties gradually lost interest in harnessing Iceland's water, the rent stopped, and in 1928 the rental agreement became void. The Icelandic government bought Gullfoss in 1945; Einar Guðmundsson of Brattholt gave neighboring land in 1974 and 1976; a memorial to Sigríður was built at the falls in 1978, and Gullfoss was protected on 9 March 1979.

The waterfall makes lots of spray.

The wet spray helps little plants grow. Mosses and berry plants grow near the falls.

The spray from the waterfall keeps the ground around it damp, and that helps many kinds of plants grow. Berry heather, mosses and low scrub are easy to spot.

Gullfoss is high above the sea, so the growing season is short and the plants are fragile. When people walk off the paths, the damaged ground can take a long time to heal. The reserve protects the plants, and symbols around it ask visitors to keep to the paths.

The reserve protects the ecosystems and vegetation as well as the falls and canyon, because the spray creates growing conditions for numerous plants; berry heather, mosses and scrub are prominent. At 191 m above sea level the vegetation is fragile and the growing period short, so vegetation erosion recovers slowly, and the many unofficial paths in the reserve take a long time to heal.

The management plan notes that lupine grows near Gullfoss and that the agency is working to remove it from the reserve. It also records that farms once thrived on the east bank, with seven now-deserted farms in an area called Hvítárhvammar, and that Hekla eruptions and soil erosion probably played a part in ending most settlement above the falls.

Lots of people come to see Gullfoss.

Stay on the path and behind the ropes. In winter the path can be icy, so some parts close.

Gullfoss is a nature reserve. Walkers are welcome if they behave well, and the rules protect it: no driving off the roads and marked tracks, no cutting plants, no disturbing animals and no damaging the rocks. Flying a drone needs permission.

Safety lines run along the paths to keep people away from the cliff edges. In winter, when it is icy, paths down to the falls can be closed. Stay on the paths and behind the lines, and hold on to a grown-up.

Reserve rules (Environment Agency of Iceland): construction and ground disturbance need the agency's permission; walkers are welcome with good conduct; driving off roads and marked trails is prohibited; so is cutting vegetation, disturbing wildlife or damaging geological formations; drones need a permit.

The management plan reports safety lines along every footpath to keep people from cliff edges, yet many visitors cross them, and visitors repeatedly pass winter closures down to the falls despite ice. The plan, written in 2016, estimated Gullfoss's visitors at about the same as Geysir's 1.1 million between July 2014 and June 2015, with several thousand on busy days.