Þjórsá Lava

[3][4] The Þjórsá Lava does not appear on the surface until 70 km (43 mi) downstream of its identified eruptive area.

[3] In the lowlands of South Iceland the lava has overflown wide areas, covering the districts Landsveit, Gnúpverjahreppur, Skeið and Flói.

Along with the rising sea level the ocean has transgressed the lava front so its border line is submerged several hundreds of metres off-shore and its littoral zone can be inspected along the beach.

The Þjórsá Lava was erupted in the Veiðivötn (Thjorsarhraun) region, Central Iceland, 8600 years BP (6650 BCE ± 50 BC).

[4] The Þjórsá lava is plagioclase-porphyritic,[2] with large light coloured feldspar phenocrysts sitting in a dark, fine grained ground mass.

The great Þjórsá lava field is shown here in red where it can be seen on the surface. In the Veiðivatn area it is covered by younger lava (Map by Guðmundur Kjartansson, geologist)