<p>Mantle plumes are part of the movement driving plate tectonics.  These movements push continental plates apart making oceans.  It's not that they occur in oceans, they cause oceans.  As pointed out in a comment, the Afar spot in Africa is not under an ocean, but it is causing the rift valley in Africa, which is full of lakes, which given geological time will connect and result in the continental plates separating and the remaining space filling with water.</p>

CC BY-SA 4.0
2023-10-13T14:13:18.770Z
2023-10-13T14:13:18.770Z
Josh King
<p>Having a look at the attached image (original at <a href="https://commons.wikimedia.org/wiki/File:CourtHotspots.png" rel="nofollow noreferrer">Wikipedia Hot Spot page</a>) I noticed that all mantle plumes originating from lower mantle (in red) are under oceans. Why?</p>
<p><a href="https://i.sstatic.net/DdGyP.png" rel="nofollow noreferrer"><img src="https://i.sstatic.net/DdGyP.png" alt="enter image description here" /></a></p>

CC BY-SA 4.0
2023-10-11T11:50:04.553Z
Two comments: 1/ Afar is not (yet) under an ocean; 2/ These are *hotspots*, not mantle plumes. Hotspots are surface expression of mantle plumes, but not all plumes have already reached the surface. So from this figure one cannot say that *all* deep mantle plumes are under oceans. Some might be under land but have not yet reached the surface—thus have not yet created a hotspot.
Jean-Marie Prival
CC BY-SA 4.0
2023-10-20T06:53:28.933Z
It would be nice to know what the different colors for the dots mean. I notice about half of the large red dots occur at boundaries of tectonic plates.
Fred
<geology><volcanology><mantle-plumes>
Why are all lower mantle plumes under oceans?
Leos Ondra
# Why are all lower mantle plumes under oceans?

(Asked by: username_0 on 2023-10-11)

Having a look at the attached image (original at [Wikipedia Hot Spot page](https://commons.wikimedia.org/wiki/File:CourtHotspots.png)) I noticed that all mantle plumes originating from lower mantle (in red) are under oceans. Why?

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

**Tags:** geology, volcanology, mantle-plumes

> **Comments:**
> **username_1**: Two comments: 1/ Afar is not (yet) under an ocean; 2/ These are *hotspots*, not mantle plumes. Hotspots are surface expression of mantle plumes, but not all plumes have already reached the surface. So from this figure one cannot say that *all* deep mantle plumes are under oceans. Some might be under land but have not yet reached the surface—thus have not yet created a hotspot.  
> **username_2**: It would be nice to know what the different colors for the dots mean. I notice about half of the large red dots occur at boundaries of tectonic plates.  

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## 1 answers

### Answer by username_3 on 2023-10-13. Score: 3

Mantle plumes are part of the movement driving plate tectonics. These movements push continental plates apart making oceans. It's not that they occur in oceans, they cause oceans. As pointed out in a comment, the Afar spot in Africa is not under an ocean, but it is causing the rift valley in Africa, which is full of lakes, which given geological time will connect and result in the continental plates separating and the remaining space filling with water.


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