The geology of the Wrekin and its immediate area is complex, consisting of a variety of rocks of a range of ages affected by numerous faults. The crest of the Wrekin's ridge and its northwestern slopes are formed from various rocks of volcanic origin assigned to the Uriconian series, of Precambrian age. The 'Uriconian Volcanics' include rhyolites, tuffs and agglomerates. These rocks - layers of ancient lava flows laid down in a volcanic island arc, similar to modern Japan - are approximately 680 million years old.