Ever heard of Jones Valley? If you visit, live, or work in downtown Birmingham, you’ve spent time on the floor of this valley. Jones Valley is the long valley lying along the northern side of Red Mountain. It was an ideal place to build an industrial city, given the nearby abundance of the three ingredients for making iron and steel (learn more here), the abundance of water in the valley’s streams, and the low elevation, perfect for railroads. So that explains why Birmingham was founded there, but where did the valley come from?
The valley’s origins began with the formation of the Southern Appalachian Mountains. Jones Valley is part of the Valley and Ridge Physiographic Province, a large region of long ridges and valleys stretching from the Birmingham area to New York. This tortuous topography developed as the Appalachians formed due to the collision of several continents, including North America, Africa, and South America.
This slow-motion collision began about 318 million years ago and continued for about 60 million years (learn more here). In the Valley and Ridge, the earth’s crust was squeezed into elongated upward and downward folds. In other areas of the province, massive sections of the earth’s crust broke from the pressure and – through a process known as thrust-faulting – were pushed up and away from the collision zone. The mountains created through both processes were once steep and tall, but millions of years of erosion have worn them down to the narrow ridges of durable rock that constitute the area’s mountains. Between these long ridges are intervening valleys, one of which is Jones Valley.
If you really want to impress your friends with your nerdy geology knowledge, you can explain to them that Jones Valley is an anticlinal valley. Such valleys formed where there were upward folds of the earth’s crust, creating something like an elongated dome. The dome’s rocks fractured with the folding, and erosion over hundreds of millions of years washed these rocks away. The sediments became portions of the Coastal Plain Physiographic Province and also offshore deposits in the Gulf of Mexico. The southern base of this dome is Red Mountain, while the northern base is a broken series of hills known by several names, including West Red Mountain and Sand Mountain (not to be confused with the large plateau of the same name in northeastern Alabama). The lowland between these corresponding ridgelines is divided into several valleys, including Jones and Opossum.
-R. Scot Duncan