<p>If you extend your map out a little bit further, you will see that the Brooks Range is just a continuation of the Rocky Mountains into Alaska.  </p>

<p><img src="https://www.freeworldmaps.net/northamerica/northamerica-physical-map-highres.jpg" alt="North America mountains"></p>

<p><em>Source: <a href="https://www.freeworldmaps.net/northamerica/" rel="nofollow noreferrer">freeworldmaps.net</a>, ©Daniel Feher (explicitly permitted use <a href="https://www.freeworldmaps.net/about.html" rel="nofollow noreferrer">here</a>)</em></p>

<p>The Brooks Range was formed at the same time as the front ranges of the Rockies in Canada and the Lower 48, during the <a href="https://en.wikipedia.org/wiki/Laramide_orogeny" rel="nofollow noreferrer">Laramide Orogeny</a> which lasted from abut 80 million years ago to about 35 million years ago.  This was caused by the subduction of oceanic plates (mainly the <a href="https://en.wikipedia.org/wiki/Farallon_Plate" rel="nofollow noreferrer">Farallon Plate</a> but also the <a href="https://en.wikipedia.org/wiki/Kula_Plate" rel="nofollow noreferrer">Kula Plate</a>, and to a lesser extent, the Pacific Plate) beneath the west coast of North America.</p>

<p>The Farallon plate went <a href="https://en.wikipedia.org/wiki/Flat_slab_subduction" rel="nofollow noreferrer">under North America at a shallow angle</a>; because of this, a large part of Western North America was uplifted, deep into the continent, with faults pushing ancient basement rocks up where the Front Ranges and the Brooks Range are today. </p>

<p><img src="https://upload.wikimedia.org/wikipedia/commons/4/48/North_America_subduction1.jpg" alt="Plates 55 Ma"></p>

<p>Pacific Ocean plates, 55 Ma. <em>Source: Wikimedia Commons</em></p>

<p>The Kula plate is "all gone", and the Farallon Plate is mostly gone, except for a few remnants like the Juan de Fuca Plate. Because of the different direction that the Pacific Plate moves, subduction ialong the West Coast is mostly gone as the Pacific Plate slides past North America. The shallow subduction that created mountains deep in the interior is done.  A subduction zone further west has created the Aleutian volcanic arc, but this is a much steeper subduction.</p>

CC BY-SA 4.0
2019-08-04T06:36:10.803Z
I wonder what’s the cause for the valley that separates the Brooks range from the rest of the mountains
Gimelist
CC BY-SA 4.0
2019-08-04T12:40:28.617Z
@Gimelist If you look further south, you'll see other outliers such as the Bighorns Mountains and the Front Range.
Spencer
CC BY-SA 4.0
2019-08-05T06:01:51.793Z
@Gimelist: By "rest of the mountains", do you mean the Alaska Range or the Mackenzie Mountains?
jamesqf
CC BY-SA 4.0
2019-08-03T05:17:12.193Z
2019-08-03T06:16:43.243Z
2019-08-03T06:16:43.243Z
Spencer
<p>This here is a map of the Brooks Range in northern Alaska:</p>

<p><a href="https://i.sstatic.net/mWa6M.jpg" rel="nofollow noreferrer"><img src="https://i.sstatic.net/mWa6M.jpg" alt="enter image description here"></a></p>

<p>As you can see, it is an inland range shaped in a downward curve.  Why is that?  What is the history of the uplift of the Brooks Range?  How and when did a piece of sea or lowland rise up into a downward-curving mountain range far from the coast?</p>

<geology><mountains><mountain-building>
What is the History of the Brooks Range?
JohnWDailey
# What is the History of the Brooks Range?

(Asked by: username_0 on 2019-08-03)

This here is a map of the Brooks Range in northern Alaska:

[![enter image description here](https://i.sstatic.net/mWa6M.jpg)](https://i.sstatic.net/mWa6M.jpg)

As you can see, it is an inland range shaped in a downward curve. Why is that? What is the history of the uplift of the Brooks Range? How and when did a piece of sea or lowland rise up into a downward-curving mountain range far from the coast?

**Tags:** geology, mountains, mountain-building


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## 1 answers

### Answer by username_1 on 2019-08-03. Score: 3

If you extend your map out a little bit further, you will see that the Brooks Range is just a continuation of the Rocky Mountains into Alaska.

![North America mountains](https://www.freeworldmaps.net/northamerica/northamerica-physical-map-highres.jpg)

*Source: [freeworldmaps.net](https://www.freeworldmaps.net/northamerica/), ©Daniel Feher (explicitly permitted use [here](https://www.freeworldmaps.net/about.html))*

The Brooks Range was formed at the same time as the front ranges of the Rockies in Canada and the Lower 48, during the [Laramide Orogeny](https://en.wikipedia.org/wiki/Laramide_orogeny) which lasted from abut 80 million years ago to about 35 million years ago. This was caused by the subduction of oceanic plates (mainly the [Farallon Plate](https://en.wikipedia.org/wiki/Farallon_Plate) but also the [Kula Plate](https://en.wikipedia.org/wiki/Kula_Plate), and to a lesser extent, the Pacific Plate) beneath the west coast of North America.

The Farallon plate went [under North America at a shallow angle](https://en.wikipedia.org/wiki/Flat_slab_subduction); because of this, a large part of Western North America was uplifted, deep into the continent, with faults pushing ancient basement rocks up where the Front Ranges and the Brooks Range are today.

![Plates 55 Ma](https://upload.wikimedia.org/wikipedia/commons/4/48/North_America_subduction1.jpg)

Pacific Ocean plates, 55 Ma. *Source: Wikimedia Commons*

The Kula plate is "all gone", and the Farallon Plate is mostly gone, except for a few remnants like the Juan de Fuca Plate. Because of the different direction that the Pacific Plate moves, subduction ialong the West Coast is mostly gone as the Pacific Plate slides past North America. The shallow subduction that created mountains deep in the interior is done. A subduction zone further west has created the Aleutian volcanic arc, but this is a much steeper subduction.

> **Comments:**
> **username_2**: I wonder what’s the cause for the valley that separates the Brooks range from the rest of the mountains  
> **username_1**: @username_2 If you look further south, you'll see other outliers such as the Bighorns Mountains and the Front Range.  
> **username_3**: @username_2: By "rest of the mountains", do you mean the Alaska Range or the Mackenzie Mountains?  

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