The Searing Gorge is a contested zone in the Eastern Kingdoms for players in the 40-60 range. It is home to a group of exceptionally stout dwarves called the Thorium Brotherhood, who have split from the Dark Iron Clan. Except for them, the Dark Iron Clan have 2000+ dwarves in the gorge working on various things and also keeping a watching eye on the Thorium Brotherhood.
For the Alliance, the entrance to the Searing Gorge in Loch Modan is locked until the Key to Searing Gorge is obtained via a quest line that culminates in At Last! (level 48 quest). However, any Rogue with lockpicking of at least 225 can pick the doors. An alternate path can be found in the Badlands just south of Kargath. This is the primary Horde entrance, as they have no way of obtaining the key.
Just as Blackrock orcs and their allies dominate Burning Steppes, so Dark Iron dwarves dominate the Searing Gorge. A large population of Dark Iron dwarves, War Golems, and Elementals resides in this dark, mountainous area.
The climate is very similar to Burning Steppes, as it was the same catastrophe that blackened both: the summoning of Ragnaros. The Searing Gorge is a part of Khaz Modan. Before being shattered by the summoning it was a mountainous region, part of the Redridge Mountains.
Large mining operations take place in The Cauldron, a giant excavation site forming a huge rift in the middle of the Searing Gorge. The Slag Pit lies within The Cauldron and is an underground mining site rich with multiple types of ore. The mining work is mainly done by slave labour, which consists for the most part of captured enemies.
Ever since the Dark Iron dwarves' capital, Thaurissan, was destroyed by the summoning of Ragnaros, they have searched for a landmass to control for their filthy, industrious works. The Searing Gorge was the obvious choice due to a low military presence, scarce population, few settlements, and high vulnerability. The dwarven garrisons were soon overrun by a massive Dark Iron invasion which forced them to retreat to Loch Modan and seal the passage.
This area was normally sealed, and adventurers could only enter by traversing through Blackrock Mountain or by obtaining the Key to Searing Gorge, which follows a series of quests. Recently, however, the Horde garrisons stationed at Kargath, in the Badlands, have grown curious about the use of the area for tactical purposes, and have cut a narrow pass through the mountains south of their encampment.
Recently, the Thorium Brotherhood built a settlement in this area called Thorium Point.