3141: Mantle Model

2025-09-19T07:03:27Z

Underdevelopedprefrontalcortex: Earth surface -> Earth's surface in transcript, fixes error

{{comic
| number = 3141
| date = September 12, 2025
| title = Mantle Model
| image = mantle_model_2x.png
| imagesize = 527x317px
| noexpand = true
| titletext = Mantle plumes explain Hawaii, Yellowstone, Iceland, the East African Rift, the Adirondack uplift, the Permian extinction, the decline of Rome, the DB Cooper hijacking, and the balrog in Moria. Those little hills of sand in your yard are caused by antle plumes.
}}

==Explanation==

A {{w|mantle plume}} is a flow of {{w|magma}} upward from deep in the Earth toward the surface. Some plumes are thought to come close to the surface and result in a variety of interesting geological features, from shield volcanoes to super volcanoes to localized uplift and subsequent crustal deflation. To a non-expert, these various features do not seem to share many common features, so it may seem surprising and confusing that mantle plumes could account for all of them. Randall implies that this is simply a form of hand-waving used by geologists for anything where there isn't otherwise a good explanation, to the point where they account for every surface feature on Earth that we can't otherwise account for, which is absurd. He lists a number of features supposedly resulting from plumes, ranging from the real, to the unrelated, to the fictional.

The title text extends this further, suggesting with increasing absurdity that mantle plumes account for other things that don't have a direct explanation:
* {{w|Hawaii}}. A {{w|Hotspot (geology)|hotspot}}, hypothesized to sit atop a mantle plume, did indeed create the Hawaiian Islands.
* {{w|Yellowstone}}. This area of hot springs, geysers, and other geothermal phenomena is in the {{w|Yellowstone Caldera}}, which some geologists believe sits atop a mantle plume.
* {{w|Iceland}}. Essentially the same as Hawaii, except for being at the edge of two {{w|tectonic plates}} instead of in the middle of one.
* The {{w|East African Rift}}. This area in East Africa is a developing divergent tectonic plate boundary where the African plate is in the process of splitting into two tectonic plates. Mantle plumes and hotspots have been theorized to have initiated and continued this divergence.
* The {{w|Adirondack_Mountains#Geology|Adirondack uplift}}. The Adirondack Mountains began uplifting in the past 10 million years. This orogeny is not related to the original {{w|Appalachian orogeny}}, which began much earlier, 325-260 million years ago. A leading theory about the Adirondack uplift is that it's driven by a hotspot atop a mantle plume.
* The {{w|Permian extinction}}, also called the 'Great Dying' and more formally as the Permian-Triassic extinction event, is the largest of the {{w|List of extinction events|"big five" mass extinctions}} since vertebrate life appeared on Earth. There are several hypotheses as to why it happened, the foremost one of which, {{w|Siberian Traps}} volcanism, is thought to have happened because of a mantle plume.
* The decline of Rome refers to the end of the {{w|Roman Empire}}, or, more specifically, of the original and western capital city of {{w|Rome}}. The decline was a complex issue caused by many non-mantle-plume-related factors, including changing social pressures, financial exhaustion after a series of wars, pressure from neighboring rivals, and siphoning of resources and attention to the newer, eastern capital city of {{w|Constantinople}}.
* The {{w|DB Cooper}} airplane hijacking occurred in 1971 and remains unsolved. Dan Cooper is an alias of the hijacker, whose real name is unknown. This is one of several xkcd cartoons referring to [[D.B. Cooper]], including [[1400: D.B. Cooper]], in which Cueball suggested that Cooper might have become filmmaker {{w|Tommy Wiseau}}, and [[2498: Forest Walk]], in which Cooper is seen stuck in a tree on [[Beret Guy]]'s property. The hijacking itself had nothing to do with mantle plumes.
* The {{w|balrog}} in {{w|Moria, Middle-earth|Moria}} is a fictional beast in {{w|J.R.R. Tolkien}}'s {{w|legendarium}} that first appeared in ''{{w|The Lord of the Rings}}''. It too has nothing to do with mantle plumes, but it was revealed by the dwarves, who "delved too greedily and too deep and awoke a terror of shadow and flame." If we were to delve sufficiently greedily and deep that we dug into a mantle plume, we would indeed be greeted by a terrible amount of flame, although the shadow aspect is unconfirmed.{{cn}}
* Antle plumes (in the title text) are a pun on "ant" and "mantle plumes". These little sand hills are probably actually {{w|anthills}} ("ant-hill plumes") and are created by ants at the entrances to their underground nests from the material excavated from their tunnels.

==Transcript==
{{incomplete transcript|Don't remove this notice too soon.}}

:[A diagram of the Earth’s inner structure is shown with the caption “Standard geophysical model of the mantle”. Dotted lines forming structures that appear to be moving through and between various layers of the mantle are labeled with arrows. The arrows either point to the base of the structures on the inside of the planet or formations on the outside.]

:[In the center around the Earth’s core are vertical columns rising up away from the core through cracks in lower layers of mantle. At different layers the structure either branches out horizontally between layers or again vertically through additional cracks. This process might yield a single vertical column, or several branching horizontal and vertical branches.]
:[These structures are labeled:]
:Hypothesized mantle plumes

:[On the Earth’s surface are various rock formations that align with the locations of plumes just below.]
:[The formations are labeled:]
:Every feature of the Earth's surface that we have a hard time explaining

:[Caption below the panel:]
:Standard geophysical model of the mantle

{{comic discussion}}<noinclude>
[[Category:Geology]]
[[Category:Biology]]
[[Category:LOTR]]
[[Category:Comics featuring D. B. Cooper]]

explain xkcd - User contributions [en]

3141: Mantle Model