Jökulsá(yö`külsou), name of several Icelandic rivers formed by glaciers. The best known is the Jökulsá á Fjöllum, which rises on the north slope of the VatnajökullVatnajökull
, glacier, c.3,150 sq mi (8,160 sq km), SE Iceland; largest glacier in Europe. At an elevation of from 4,200 to 6,100 ft (1,280–1,860 m), it covers a huge volcanic plateau, which includes the Grímsvötn caldera, Iceland's third largest and
..... Click the link for more information. in SE Iceland and flows c.130 mi (210 km) N into the Öxarfjörður bay, forming the Dettifoss, one of four waterfalls on the river and one of Europe's most powerful waterfalls, c.30 mi (50 km) from its mouth; below the falls, the falls the river flows through the Jökulsárgljúfur, a canyon that is 390 ft (120 m) deep in places.