transition-traps

Updated: July 20, 2026

Here, then, is a connexion sufficiently close established between the phonolites and the green slates, between the pyroxenic amygdaloids and the serpentines containing copper-ores, between volcanic substances and others that are included under the vague name of transition-traps. All these masses are destitute of quartz like the real trap-porphyries, or volcanic trachytes.

Alexander von Humboldt - Personal Narrative of Travels to the Equinoctial Regions of America, During the Year 1799-1804 — Volume 2