A land of harsh climates and harsh people, in the time of the Light water would flow from Volantis to Thalassa due to there relative proximity. Since the light ended the water has stopped flowing as much, where once it was a torrential river navigable by brave sailors in sturdy ships now it is essentially perpetual light rain flowing between the two. Thalassa remains a land of barren steppe and harsh mountains, it has relatively few populated areas, mostly focussing around where the water flows from Volantis. It's only appreciable industries are mining and water capture along the band where the water falls from Volantis. Many corporations and peoples have tried to colonise the further parts of Thalassa with limited success, the defining factor being access to fresh water. With the advent of Red Amber powered pumps and pipelines this has become less of a problem, but in reality, unless something amazing were discovered in the wastes, no one will bother.
Rocks and minerals.