<p>Short answer: <strong>yes, there are other mountains which contains oceanic crust in their lithologies</strong>.</p>

<p>The process you described as "the upthrust of ocean crust" is called <a href="https://en.wikipedia.org/wiki/Obduction" rel="nofollow noreferrer">obduction</a>. The resulting rock sequence is called an <a href="https://en.wikipedia.org/wiki/Ophiolite" rel="nofollow noreferrer">ophiolite</a>. As you can see <a href="https://en.wikipedia.org/wiki/List_of_ophiolites" rel="nofollow noreferrer">here</a>, there is quite a lot of them around the world! One of the most studied is the Oman ophiolite. I have seen the Chenaillet ophiolite in the French Alps, it's quite spectacular.</p>

<p>Note that ophiolites usually include not only basalts (often in form of pillow lavas, typical of emplacement under the ocean), but also other oceanic crust lithologies such as gabbros, and even the underlying lithospheric mantle, often as serpentinite (a peridotite altered by water).</p>

<hr>

<p>Edit:</p>

<p>I found a  <a href="https://archive.usgs.gov/archive/sites/geomaps.wr.usgs.gov/parks/olym/content.html" rel="nofollow noreferrer">Guide to the Geology of Olympic National Park</a> on the USGS website. Unfortunately some links are dead, but you can still find lots of information on the range's lithology and formation. The page on <a href="https://archive.usgs.gov/archive/sites/geomaps.wr.usgs.gov/parks/olym/olym5.html" rel="nofollow noreferrer">"basalt and its associated rocks"</a> mentions the presence of gabbro (a magmatic rock with the same composition as basalt but a crystalline texture due to slower cooling), but not that of any mantle rock. According to this other page on <a href="https://archive.usgs.gov/archive/sites/geomaps.wr.usgs.gov/parks/olym/olym14.html" rel="nofollow noreferrer">"colliding plates and Olympic rocks"</a>, the basalt is not from the oceanic crust itself but rather from a submarine volcano emplaced avove the plate (fig. 26). So, <strong>the Olympic Mountains would not be an ophiolite per se, but rather an accretionary wedge</strong>, i.e. "a thick wedge of rocks produced by the progressive offscraping of ocean floor sediments during subduction and their accretion to the continental margin" (excerpt from the guide's preface).</p>

CC BY-SA 4.0
2020-01-24T17:51:37.797Z
So do you know if the Olympic mountains are an ophiolite sequence? What I've read about them is that they were formed by obduction but contain no granitic rock whatsoever.
Mr X
CC BY-SA 4.0
2020-01-27T10:43:04.900Z
I've looked it up and it appears that they are actually not a true ophiolite sequence (which never contains granite, only basic to ultrabasic rocks). It's more an accretionary wedge that contains a submarine volcano among the sediments, I've updated my answer to clarify this.
Jean-Marie Prival
CC BY-SA 4.0
2020-01-23T10:10:58.963Z
2020-01-27T12:07:11.530Z
2020-01-27T12:07:11.530Z
Jean-Marie Prival
<p>So it is my understanding the Washington's Olympic Mountains are basaltic mountains. The reason is that they formed from the upthrust of Ocean crust rather than continental crust as the Farallon plate was pushed under the North American plate. Are there any other mountain ranges (worldwide), particularly coastal ranges made of basalt oceanic crust, that have roughly the same geology?</p>

<mountains><subduction><orogeny>
Are the Olympic Mountains (in Washington state) geologically unique?
Mr X
# Are the Olympic Mountains (in Washington state) geologically unique?

(Asked by: username_0 on 2019-08-29)

So it is my understanding the Washington's Olympic Mountains are basaltic mountains. The reason is that they formed from the upthrust of Ocean crust rather than continental crust as the Farallon plate was pushed under the North American plate. Are there any other mountain ranges (worldwide), particularly coastal ranges made of basalt oceanic crust, that have roughly the same geology?

**Tags:** mountains, subduction, orogeny


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## 1 answers

### Answer by username_1 on 2020-01-23. Score: 5 | Accepted answer

Short answer: **yes, there are other mountains which contains oceanic crust in their lithologies**.

The process you described as "the upthrust of ocean crust" is called [obduction](https://en.wikipedia.org/wiki/Obduction). The resulting rock sequence is called an [ophiolite](https://en.wikipedia.org/wiki/Ophiolite). As you can see [here](https://en.wikipedia.org/wiki/List_of_ophiolites), there is quite a lot of them around the world! One of the most studied is the Oman ophiolite. I have seen the Chenaillet ophiolite in the French Alps, it's quite spectacular.

Note that ophiolites usually include not only basalts (often in form of pillow lavas, typical of emplacement under the ocean), but also other oceanic crust lithologies such as gabbros, and even the underlying lithospheric mantle, often as serpentinite (a peridotite altered by water).

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Edit:

I found a [Guide to the Geology of Olympic National Park](https://archive.usgs.gov/archive/sites/geomaps.wr.usgs.gov/parks/olym/content.html) on the USGS website. Unfortunately some links are dead, but you can still find lots of information on the range's lithology and formation. The page on ["basalt and its associated rocks"](https://archive.usgs.gov/archive/sites/geomaps.wr.usgs.gov/parks/olym/olym5.html) mentions the presence of gabbro (a magmatic rock with the same composition as basalt but a crystalline texture due to slower cooling), but not that of any mantle rock. According to this other page on ["colliding plates and Olympic rocks"](https://archive.usgs.gov/archive/sites/geomaps.wr.usgs.gov/parks/olym/olym14.html), the basalt is not from the oceanic crust itself but rather from a submarine volcano emplaced avove the plate (fig. 26). So, **the Olympic Mountains would not be an ophiolite per se, but rather an accretionary wedge**, i.e. "a thick wedge of rocks produced by the progressive offscraping of ocean floor sediments during subduction and their accretion to the continental margin" (excerpt from the guide's preface).

> **Comments:**
> **username_0**: So do you know if the Olympic mountains are an ophiolite sequence? What I've read about them is that they were formed by obduction but contain no granitic rock whatsoever.  
> **username_1**: I've looked it up and it appears that they are actually not a true ophiolite sequence (which never contains granite, only basic to ultrabasic rocks). It's more an accretionary wedge that contains a submarine volcano among the sediments, I've updated my answer to clarify this.  

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