Fold mountains

How are mountains formed? The 4 main types of mountains

I don’t remember why we chose geology.

It was our freshman year at the University of Tennessee. My friend Hobby and I needed a science lesson.

I imagine that class time – not too early, not too late – was heavily factored into our decision-making.

But it was one of the best decisions I made during my time at UT. It was a terrific class. I found the study of geology fascinating.

And while I don’t have a reason to use geology a lot in my day-to-day life, I’ve found it to be great for little daddy facts that I’m sure the kids love .

As we drive along I-40 through the mountains of North Carolina, I talk to the kids about angles of repose and how rockslides happen. Additionally, I point out where landslides have occurred and what they have done to repair them.

When we are along the mountain streams, they might hear about the different types of rocks. These include metamorphic rocks, igneous rocks, and sedimentary rocks, in case you forgot in your college science books.

Road trips can include a discussion of tectonic forces or the highest peak in the Smokies versus the highest point in the contiguous United States – which is Mount Rainier in the western United States if you’re keeping score at home.

Now, to be clear, two semesters of student-level geology 30 years ago doesn’t make me an expert. I picked up just enough anecdotes about the geological formations to really boost my dad’s points.

Anytime you can talk about volcanic activity while driving in the Smokies, that’s a bonus.

Morton’s Overlook is a great place to take in mountain views, located below Newfound Gap on the border of Tennessee and North Carolina (Photo by Natural Stock/

Expect. Are the Smoky Mountains volcanic?

No they are not.

But talking about volcanic mountains gives me a chance to work on my Dr. Evil pronunciation of “magma” and a dad has to work his stuff where he can.

Also, it was basically a rumor that started as an April Fool’s Day prank on the internet.

Also read: Are there volcanoes in Tennessee? Answers to your burning questions

Fog over the Great Smoky Mountains
The Smokies are fold mountains, and they were once much taller than they are now (Photo by Robert Gubbins/

If the Smokies aren’t volcanic, how did they form?

We’re not going to rely on my 30-year-old freshman geology class for this one.

The Smokies are what we call folded mountains.

According to our friends at National Park Servicethe Smokies started somewhere between 310 and 245 million years ago.

The movement of the planet’s tectonic plates, which create mountainous forms, brought the eastern edge of the North American plate against the African tectonic plate, creating part of the supercontinent known as Pangea.

Basically, continental plate collisions occur at the rate of a few centimeters per year and continue over millions of years.

There is evidence of earlier plate tectonic geologic events in the rocks of the Great Smoky Mountains.

Hiker walking with Rocky Mountains in view
The Rocky Mountains, pictured above, are a younger mountain range than the Smokies (Photo by Alaina O’Neal/

Did you know the Smokies were bigger?

The NPS indicates that Appalachia was once likely much higher than it is today. In fact, the elevations were probably similar to our younger western cousins, the Rocky Mountains.

During a “last great episode of mountain building”, older, buried rocks were pushed up and over younger rocks and left a flat thrust fault, known as the Great Smoky Fault , according to the NPS.

After that, Pangea broke up. Then the major tectonic plates shifted into the positions they are today.

cave falls
Most of the park’s beautiful waterfalls have formed where descending streams have met ledges of resilient metasandstone, according to the NPS (Photo by Andrew S/

The ancient ancestors of the Smokies

The NPS indicates that the new rugged highlands, after the breakup of Pangea, have been subject to intense erosion by ice, wind and water.

The eroded sediments were transported to the Atlantic Ocean and the Gulf of Mexico via rivers and streams.

The rock layers most resistant to erosion formed the highest peaks in the Smokies, such as the hard metasandstone atop Clingmans Dome.

Today, geologists believe that the mountains are eroding two inches every thousand years.

This process transformed what we know as the Smokies, in fact, all of the Appalachian Mountains, into the relatively small mountains they are today.

What are the types of mountains?

A mountain is generally considered to be at least 1,000 feet above sea level. The main types include:

  1. volcanic mountains
  2. Folded Mountains
  3. Mountains of faulted blocks
  4. distorted mountains

The different types of mountains are essentially created by the same process under the earth’s crust. Specifically, plate movements and volcanic eruptions.

Mountain ranges are generally classified according to the processes that created them. However, they are all the result of plate tectonics in one way or another.

Traveler looking at Padar island on a volcanic mountain
Padar Island is home to a volcanic mountain in Indonesia (Photo by B_Beum/

1. Volcanic mountains

Volcanic mountains are probably the easiest to understand. Moving plates create volcanoes. This break in the Earth’s crust allows lava and other “bad stuff” to escape from the magma chamber beneath the Earth.

The Pacific Ring of Fire is the best-known group of volcanoes that runs along western North America, South America, and East Asia.

Essentially, it’s the edge of the Pacific Ocean. Volcanoes are mostly found on the ocean floor along the mid-ocean ridges of tectonic plates.

Examples include Mount St. Helens in North America and Mount Kea and Mount Loa in Hawaii.

View from Cades Cove
The Smokies, seen at Cades Cove, are an example of folded mountains (Photo by Morgan Overholt/

2. Folded Mountains

When plates collide, one plate can slide under the other – an action called subduction.

When this happens, the plates warp and bend, forming mountains. Most of the major continental ranges, including our Smokies, are folded mountains created by subduction zones.

Mount Everest and the Alps in Europe are folded mountains. In fact, fold mountains are the most common type of mountain on earth, according to world atlas.

tetons in wyoming lake front
The Tetons in Wyoming are an example of boulder fault mountains (photo by Pat Tr/

3. Mountains of faulted blocks

And now we’re really starting to understand why I didn’t take a geology course in sophomore year. It’s just one definition after another as the actual concept gets further and further away from my understanding.

But essentially, boulder fault mountains are the result of a fault – a linear area where the lithosphere is separated. What is the lithosphere?

It is the outermost rigid rocky shell of a terrestrial planet. Basically, it is the upper part of the Earth’s surface.

As this separates, magma and volcanic substances can break through. Block fault mountains can be volcanic, but they don’t have to be.

The Tetons of Wyoming are an example of block fault mountains.

Black Elk Peak Custer SD State Park
Black Elk Peak at Custer State Park in South Dakota’s Black Hills Area is an example of an undistorted mountain (photo by Exploring and Living/

4. Warped Mountains

Warped mountains are kind of like the end of a chain-reaction car crash. They form away from the collision site where the pressures are not as severe.

This creates mountains with domed structures or domed mountains. The Black Hills of South Dakota are a good example of distorted mountains.

What mountains have you visited? Let us know in the comments below.

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