I can't find Mordor on Google Earth, no matter how hard I look. GE would have been handy for the company of the ring I reckon.
Tolkien either set or continued a trend for giving his settings a map. I'm reading a fantasy book at the moment, and it's extremely derivative, right down to it's map.
Here's a version of Tolkien's world. The person that drew it has seen fit to add distances in the top left hand corner.
Fantasy writers seem to like the "League" as a unit of linear measurement. This allows them considerable scope, since you can't pin one down to any particular distance.
"The distance a man can walk in about an hour" is one description. That's about 3 miles. But if Fred Bloggs, author, says that Grebbo the Great marched his men 20 leagues in a day, he could rebut charges of cruelty by pointing out that he didn't have the men walk 60 miles, because he used the measurement from Ancient Rome. That's about 1.4 miles. So the men walked a mere 28 miles. And Grebbo bought them all ice creams.
Tolkien's Middle Earth took several months to cross, on foot, with diversions and digressions. Farting about in Lorien and Rivendell. Getting stuck in Forests and Barrows. Going too far south into Emyn Arnen. That kind of thing.
I don't remember the exact text, and I have no intention of looking it up, but at one point, some of the company get from Cair Andros to Fangorn in 3 days. A distance that an awestruck man of Rohan described as 80 leagues, or something similar.
According to the person that did the map above, the distance from Cair Andros to Fangorn is about 200 miles. So they must have done about 66.66666 miles per day. That's a fairly constant 4 miles per hour (a fast walk) for 16 hours a day.
Kind of fits the text. The poor buggers must have been knackered, but your average triathlete would laugh scornfully at them and say "Strider? You're taking the piss, mate."
So that kind of puts a scale on things. But how did it come to be as it looks? What always struck me when I looked at Tolkien's map was the mountain ranges, and how they formed neat fences around certain areas.
Mountain ranges form through vulcanism, or through tectonic plate movement. They then slowly erode again.
In this case, I'd say three plates are converging. To the west there's Eriador. It's gradually colliding with Rhovanion to the east. Meanwhile, a southern plate containing Gondor and Mordor is moving northwards, and the uplift is forming the range known as the White Mountains.
the picture is complicated by vulcanism, particularly in Mordor. The lonely mountain, where Bilbo got the better of Smaug the dragon, stands alone. A purely volcanic formation.
I'd say it's likely that the Misty Mountains in particular are subject to seismic activity, and that therefore the mines of Moria are not a good place to try to set up home.
The Sea of Rhun is almost certainly hyper-saline, although if it's from a high latitude, the rate of evaporation is likely to be lower than similar lakes in warmer climates. It's mid-continental location means it's likely to be extremely cold during the winter, and hot and dry during the summer.
Left to it's own devices, nature tends to go through a series of colonising ecosystems, which culminate in a stable forested state. With the exception of isolated pockets in places like the Shire, Minas Tirith, Isengard, etc, the population density seems extremely low. If nobody is cutting down the trees or clearing the land, why are the forests limited to such a small area?
Perhaps poor soils are responsible. Or perhaps it's because it's not real. It's a modern myth. Or because it's actually New Zealand.