Member Login. The following was included in TCTA's 2015-16 Survival Guide, the ultimate reference tool for Texas educators, and is current as of September 2015 but is subject to change.
The Allegheny Mountains run diagonally from the southwest to the northeast with piedmont and coastal plains in the southeast triangle. The Allegheny Front, as it's called, cuts a diagonal line across the state. In the northwest, the plateau falls to the Lake Erie lowlands and, finally, Lake Erie. ( Pennsylvania Close-up)
Two of the largest of the Pennsylvanian island ranges rose in Colorado. These are now known collectively as the Ancestral Rocky Mountains (ARM). The eastern ARM uplift, now known as Frontrangia, came up in central Colorado a bit west of the current Front Range uplift, while Uncompahgria occupied southwestern Colorado.