The Ring Road across Skeidarársandur, built in 1974, was the last bit of the National Highway to be constructed. Long gravel dykes have been strategically positioned to channel floodwaters away from the highly susceptible artery. They did little good, however, when in late 1996 the Ring Road bridges were washed away like matchsticks by the massive glacial lake flood (jökulhlaup) released by the Grimsvötn eruption. The glacier melts because of geothermal heat and water collects beneath the ice, which drains every few years, causing great outburst floods. There’s a memorial of twisted bridge girders and an information board just west of Skaftafell national Park.