Skjaldbreiður, meaning thebroad shieldin Icelandic, is an Icelandic mountain from whose name the term "shield volcano" derives. It was formed in a huge and protracted eruption roughly 9,000 years ago. The extensive lava fields which were produced by this eruption, flowed southwards, and formed the basin of Þingvallavatn, Iceland's largest lake, and Þingvellir...