The geological event that contributed to the formation of the Appalachian Mountains was the collision of the North American and African plates.

This collision occurred during the formation of the supercontinent Pangea, approximately 300 million years ago, leading to the uplift and folding of the Earth's crust, which created the Appalachian Mountain range. This tectonic activity resulted in the complex geological structures and diverse rock formations that characterize the Appalachians today. Over millions of years, subsequent erosion and weathering have shaped the mountains into their current form, creating the rolling hills and valleys that are iconic features of this region.