These mountains were created by convergence of the tectonic plates. The continental crust and oceanic crust of the Demon Wastes were shifted, creating the mountain range that extends the entire width of the peninsula.
The Shadowcrag Mountains border the infamous Lake of Fire Volcano. This is a very active Strato - Volcano created from continuous explosions of pyroclastics falling from the underground magma vent, shaping the falling tephra into a cone-shape.
Atop the Lake of Fire volcano is a gigantic crater, which was created by an explosion. The force of the explosion blows the material at the top of the volcano away. This volcano is so active because of its location and creation. The volcano itself was created by the tectonic process of convergence over a "hot spot". That is, an area in Eberron's crust where the pressure of the surrounding tectonic plates is so great, the area is super heated, melting the rock and mineral in that area.
Due to the pyroclastic flow off of the volcano, the area immediately surrounding has very few inhabitants. At the base of the volcano, however, exists The Labyrinth. This is a vast series of tubes and caves (250 miles wide and 700 miles long) is inhabited by the Ghaash'kala Clans. These clans consist of orcs, half orcs and humans who guard the Labyrinth and prevent anything from getting in ... or out. The Labyrinth was created by lava tubes that extended from Lake of Fire into the flatland. The tubed were exposed through a process of erosion characterized by wind off the ocean and renewed pyroclastic flow from the ever-active volcano.
These lava tubes are created from the outer shell of the lava flow being cooled by outer conditions, while the hot lava continues to course underground. When the lava has all run out, what's left is a tube with walls of hardened Pahoehoe lava.
This is a very dangerous place to live because of the volcanic activity, as well as its magical, demonic inhabitants...
