The description of the Helcaraxë in the published Silmarillion is fairly mundane, making it sound more like the Bering Straits. But the description in the Ambarkanta that Tolkien wrote in the 1930s is much more metal, so I've gone with it here. Plus, it makes sense in a flat world.
Part 262 You're not serious
Next time: Part 263: Crossing the ice
Chibis by the now-dead website formerly known as tektek.org
Partially-frozen Niagara Falls. Now imagine the water pouring over the edge of a flat earth into the void, and freezing in the cold of space.