I’m pretty sure it’s literally “Thor’s March”, where “March” is in the sense “borderland, frontier” (as in the Marches districts between England and Scotland, and between England and Wales, or Tolkien’s Westmarch of Rohan).
As for whether or not there are forests there (or for that matter elsewhere on Iceland), let me just quote a relevant UN Environmental Program report: “A recent study of the various definitions of forests (Lund 2008) found that more than 800 different definitions for forests and wooded areas were in use round the world – with some countries adopting several such definitions at the same time!”
There may not be 800 different answers to the question of Iceland’s forests’ existence, but that is because it’s a yes/no question. ;-)
It really isn’t. By Wikipedia, Loch Ness has a volume of 7.4 km³, while the biggest lake in Norway is 56.0 km³; in Sweden is 153 km³; in Turkey is 607 km³; in North America is 11,600 km³; in Africa is 18,900 km³; and in Russia is 23,600 km³. And the Caspian sea is a whooping 78,200 km³.
Loch Ness is on the small side, as big lakes go. What’s remarkable is that England has so little in the way of lakes.
“Some time last century …”