Virtual Tour of Red Mountain Cut Signs

- Photo Credit: Francesca Gross
- Photo Credit: Francesca Gross
- Photo Credit: Francesca Gross
- Photo Credit: Francesca Gross

When the trail along Red Mountain Cut was first opened the Red Mountain Museum set out signs to explain the features of this amazing natural wonder. Over the years the signs have had their share of weather and human impacts. Posted here are photos of the signs from 2012 with accompanying text. Take a virtual tour!

Falling Rocks







Where's the beach








Where’s the beach?


These reddish colored rocks are sandstones of the Red Mountain Formation, from which this mountain gets its name. The red color is caused by iron that has oxidized – rusted- due to contact with air.

Some of the individual particles making up the rock are small round grains called oolites. They were formed by the precipitation of calcium carbonate on the sand grains of an ancient beach in this spot. Algae may have played a role in transporting the iron to the site of the beach.

Where is the world







Where in the world is Acaste birminghamensis?

Trilobite: A hard-shelled marine animal resembling a pill bug or roly-poly. This trilobite, Acaste birminghamensis, is named for Birmingham, and has been found only on Red Mountain. Trilobites related to Acaste, as well as the brachiopods Stricklandia and Pentamerus, are but a few of the many fossils found only in western Europe and eastern North America. This is part of the evidence that North America and Europe were once closer together.

volcanoes in Alabama








Volcanoes in Alabama?

This thin green layer, bentonite, was formed when airborne volcanic ash settled into seawater. The location of the volcanoes that produced the ash layer has never been determined, but the bentonite layer has been found as far north as Nashville. The volcanoes may have been on the offshore islands which have since been destroyed. Because volcanic ash contains radioactive elements, this layer can be dated to about 442 million years ago.

This rock is limestone

This rock is limestone.

As rainwater sinks into the ground, it dissolves the limestone, leaving a cave beneath the ground, like the small one behind this sign. Caves near the ground surface can collapse, forming sinkholes. Much of Birmingham lies on limestone rocks, so it in possible that sinkholes could develop almost anywhere.

This is OUR fault









This is OUR fault!  

Red Mountain Fault is a break in the rock along which there has been movement. Across the highway, the blue markers indicate the same rock layers on each side of the fault.  The layers on the right have been moved upward about 25 feet compared to those on the left side. Above this sign, you can see how the same movement bent the rock layers on the right side of the fault. Movement on the fault began as early as Silurian times and continued into the Mississippian.

Steel city








Birmingham: The Steel City

Native American Indians used this red rock as a coloring agent for paint before it was identified as iron ore in the early 1800’s. Miners named this layer Kidney Seam since is reminded them of kidney beans. It is the remains of an ancient cobble beach. The bean-shaped cobbles are composed of lime-cemented sediments formed during the deposition of the sandy beach. Having iron ore, limestone and coal close by made Birmingham a successful steel producer: by 1962, more than six million tons of ore per year.

RMC NLandmark









Red Mountain Cut: A National Natural Landmark.

Red Mountain Cut is one of only three roadcuts in the U.S. that are geologically interpreted for the public.  On November 25, 1987, the Red Mountain Cut was officially designated a National Natural Landmark. Two million cubic yards of rock were removed during construction. The roadway cut is one-third mile long, with some 150 million years of geologic history exposed in the tilted rocks.

Is this rock








Is this rock?  

No this is concrete, sprayed on the road cut during construction in an attempt to prevent rock falls. Originally the entire road cut was to be covered with concrete. Fortunately, local geologist realized the road cut’s significance and had the spraying halted.

In the limelight

In the Limelight

A bed of very pure limestone occurring throughout the valley that Birmingham occupies has been heavily mined for steel production. Limestone continues to be used in road surfaces, cement, building stone and fertilizer.

Fossil Road Builders

Fossil Road Builders

The chert-flint-rocks above the white triangle are Mississippian in age, about 340 million years old. They are full of cavities formed when rainwater dissolved fossils. This hard lightweight rock drains water well because of the cavities; therefore it is frequency used as road bed material.

Dry Land at Last








Dry Land at Last

Pennsylvania aged rocks – about 320 million years old – occur farther to the south on Shades Mountain, the highest visible ridge. During the Pennsylvanian, Africa collided with North America, deforming the rocks exposed today in the Appalachian Mountains.  This collision caused the rock layers on the cut, originally horizontal; to be tilted as they are now. Gradual uplift of the region followed, accompanied by withdrawal of the sea. Because sediments are only deposited in low area like oceans, no more sedimentary rock formed here. Stream erosion carved the uplift region, into the valleys and ridges of the Appalachian Mountains.


Undersea construction crew








Undersea Construction Crew

The feature outlined in white is an ancient limestone reef. Like modern reefs, the ancient reef was formed in relatively warm, shallow sea water. Some limestone is formed by chemical action in sea water, but this reef was built by colonies of plants and animals growing from the seafloor.

Stony algae         brachiopod         coral      trilobite               crinoid

17 on the opposite side









The Cambrian section is represented by Cooper Ridge Dolomite, Ketona Ridge Dolomite, and Conasauga Limestone. The Ketona dolomite, a very pure dolomite, is the main source of ‘flux stone’ used in producing steel.

28 the white marker








28 The white marker indicates the contact between the Devonian sandstone below and the Mississippian chert above. The oldest Mississippian rock here is about 340 million years old. The chert is an altered form of limestone. Many fossils are found in this chert and in beds of mud within the chert. Some of these can be seen on the display slab.










29 The next ridge to the south _________  ________ is  underlain by Mississippi sandstone which is so pure in places that it has been mined to make glass. The other ridge further south __________ is also formed by Mississippi Sandstones. The highest ridge that can be seen to the south __________ is Shades Mountain, and is underlain by Pennsylvanian sandstone, coal and shales. The Pennsylvanian formations extend from Alabama to New York and contain many coal beds. These coals originally accumulated as peat deposits within huge swamps. These vast coal reserves of the Appalachian were one of the three basic materials needed for Birmingham’s steel industry.









The first ridge is Hartselle Sandstone. The valley between is occupied by the Tuscumbia Ls and Pride Mountain Formation. Floyd Shale forms the floor of the valley beyond. The Little Shades Sandstone member of the Parkwood formation forms the second ridge and regressive shales and sandstone of the Parkwood continue about two-third of the way up Shades Mountain.  Thick, massive sands called the Shades Sandstone Member occur in the base of the Lower Pennsylvanian Pottsville formation. Three thick sandstone members are present near the base and probably represent deposition as barrier sands.








The Stones River formation is only partial represented here because the pinnacle interrupts the depositional sequence.

Orange marker sign

The orange marker to the north indicates the boundary between dolomite (formed in a shallow sea about 485 million years ago) and limestone (deposited about 475 million years ago). The outcrop you see is a small dolomite hill that was curved by erosion about 480 million years ago when this area was on land. The top of the hill is covered with pebbles and boulders of chert. Eventually the sea returned, covering the hill, and the continual deposition of limestone cemented the pebbles to the hill top.

Cambrian section









The Cambrian section is represented by Cooper Ridge Dolomite, Ketona Ridge Dolomite, and Conasauga Limestone. The Ketona dolomite, a very pure dolomite, is the main source of ‘flux stone’ used in producing steel.