Quel'Thalas seems to make up a fourth continent in some maps. Most of the time, it appears that the Eastern Kingdoms are divided into only three continents, as Quel'Thalas is shown as part of northern Lordaeron.
Eastern Kingdoms is actually considered to be three subcontinents: Lordaeron in the north, Khaz Modan in the middle, and Azeroth (the continent) in the south. It has a variety of climates like Kalimdor, but has more zones that show damage from humanoid intervention. The Alliance dominates the central and southern parts of the continent (with the exception of Stranglethorn Vale). However, the north is the stronghold of the Forsaken and regions scarred by the Scourge.
Unlike Kalimdor, the Eastern Kingdoms have very few desert areas (except maybe the Badlands), but several areas are wastelands (the Blasted Lands, Burning Steppes, Deadwind Pass, and Searing Gorge). It has a few more specifically swampy areas like the Swamp of Sorrows and the Wetlands, but temperate forests and hills proliferate. For some reason the mountainous areas surrounding Ironforge appear to be perpetually snowy, while most of the other regions are temperate or warmer.
^Lands of Conflict, p. 17 Quote:...the Arathi assured them the land would always belong to all peoples and named the land as a whole in homage to their ancient ancestors: Azeroth. Together, the humans constructed the fortress city of Strom...
^Lands of Conflict, p. 17 Quote:The envoy explained that long after the destruction wrought by the Maelstrom, some of the survivors had made their way to northern Azeroth and established a new kingdom, called Quel’Thalas, and a new source of magical power, called the Sunwell.
^World of Warcraft manual, p.106 Quote:There are no flight paths across the ocean linking Kalimdor and Azeroth.
^Dark Council Quote:The Argus Wake might run deep through the continent of Azeroth.
^World of Warcraft: The Roleplaying Game, p.362 Quote:On both Kalimdor and Azeroth, war and time have left much of the land in ruins, and civilization is often limited to the land enclosed inside city walls.
^Dark Factions, p. 11 Quote:but they exist on coastlines throughout the world — Azeroth, Kalimdor, and Northrend all boast tribes of murlocs.