Local Effects of a Kimberlite Eruption?

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Discussion Overview

The discussion revolves around the potential local effects of a Kimberlite eruption, particularly in the context of historical events in the 1830s near Washington, Arkansas. Participants explore the implications of such an eruption on nearby populations, the characteristics of Kimberlite eruptions, and comparisons to other volcanic events.

Discussion Character

  • Exploratory
  • Debate/contested
  • Technical explanation
  • Conceptual clarification

Main Points Raised

  • One participant questions the potential danger of a Kimberlite eruption to nearby populations, suggesting that while volcanic activity would be dangerous, it might not prevent transcontinental migration.
  • Another participant references a study on Kimberlite volcanology, indicating that a significant volume of rock could be ejected through a narrow pipe at high temperatures and speeds.
  • Concerns are raised about the potential for harmful materials being launched into the stratosphere during an eruption, with references to external sources discussing the phenomenon.
  • Participants engage in calculations regarding the height that material could reach if expelled at Mach 1, exploring the implications of such dynamics.
  • There is a discussion about the nature of ash produced by Kimberlite eruptions, with some suggesting it would be cold and safe, while others question how to differentiate between safe ashfall and dangerous pyroclastic surges.
  • One participant emphasizes the importance of understanding the characteristics of different volcanic eruptions and their potential hazards, particularly in relation to the morphology of the volcano.

Areas of Agreement / Disagreement

Participants express differing views on the nature and safety of Kimberlite eruptions, with no consensus reached regarding the potential dangers they pose or the characteristics of the ash produced.

Contextual Notes

Participants reference various assumptions about the nature of Kimberlite eruptions, including the temperature and pressure conditions, as well as the geological context in which they occur. There are unresolved questions regarding the specific effects on local populations and the characteristics of the ash produced.

Malapine
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Are there any thoughts on what effects a Kimberlite eruption would have on nearby populations, if one occurred in modern history? They were supposedly quite violent based on the estimated rates of ascent of the diamond-bearing lava, but how does that translate to VEI or megatons, etc. ?

[ Specifically: in the 1830s, several key players in the Texas Revolution (Houston, Bowie, Crockett, etc.) were hanging out in Washington, Arkansas, about 15 miles south of Crater of Diamonds. If there had been an eruption at that time, could it have harmed the townspeople or made the Southwest Trail impassable? ]
 
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Any volcanic activity would be locally dangerous, but not so dangerous that it could not be bypassed, so it would not prevent transcontinental migration.

If the eruption had covered a greater area in recent times, then there would be diamonds scattered widely across the region, but the kimberlite diamond pipes are a local feature.

Diamond is a high pressure - low temperature mineral. It is unlikely that a red-hot fluid lava would be involved. It is more likely that erosion has exposed the deep kimberlite pipe, which continues to be weathered on the surface, concentrating diamonds in the soil.

Malapine said:
They were supposedly quite violent based on the estimated rates of ascent of the diamond-bearing lava, ...
Where is the reference to that high rate of ascent?
 
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Almost tektites !!
But seriously, per Wiki, 'potentially from anomalously enriched exotic mantle compositions', you'd have bad stuff launched into stratosphere, then raining down for miles around...

This 'pop-science' discussion may amuse : https://www.wired.com/2017/05/crazy-eruptions-spit-diamonds/
 
Nik_2213 said:
Almost tektites !!
How high could you get at Mach 1.0 = 343 m/s ?
KE = PE; ½·m·v² = m·g·h ; ½·v² = g·h ;
h = ½·v² / g ;
h = 0.5 * 343 * 343 / 9.8 = 6 km.
 
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Baluncore said:
How high could you get at Mach 1.0 = 343 m/s ?
KE = PE; ½·m·v² = m·g·h ; ½·v² = g·h ;
h = ½·v² / g ;
h = 0.5 * 343 * 343 / 9.8 = 6 km.
Then what form will the cloud take?
Vesuvius, on the first day, formed a pine-shaped cloud directly upwards. Ash raining down on Pompeii was cool and safe. It did eventually collapse roofs; but there was a thick layer of cold ash on Pompeii and people were still alive in strong cellars and walking on top of ashes next morning when a hot pyroclastic flow overtook and slew them all.
Whereas in St. Pierre, on 8th of May, 1902, everyone save one person in a strong cellar was killed... but from the descriptions and even photos of the next two weeks, there was little ash deposited (3...7 cm in the city?)

From a geological deposit, how do you distinguish cold (and safe) ashfall from the thin but fatal pyroclastic surge?
From the properties of volcano, how do you predict if the eruption will result in safe cold ashfalls or dangerous hot surges?
Do kimberlite eruptions produce cold ashfall or hot surges?
 
snorkack said:
From a geological deposit, how do you distinguish cold (and safe) ashfall from the thin but fatal pyroclastic surge?
From the properties of volcano, how do you predict if the eruption will result in safe cold ashfalls or dangerous hot surges?
Do kimberlite eruptions produce cold ashfall or hot surges?
I would expect kimberlite eruptions to be cold and safe. They are mostly CO2 expanding noisily near the surface. They often occur underwater or from cracks below the local topography. If they flow for long enough, a heap of ash can build up downwind.

As a neighbour, or for a graduate study project, you need to pick a volcano with a small and symmetrical cone. That will produce ash to fertilise the soil, without the risk of repeated pyroclastic flows. Ugly shaped cones, that show evidence of angry explosions, do not make good neighbours. Vulcanologists die when they cannot get away fast enough. It is safer to select a career in archaeology, once things have quietened down a little.

The most dangerous volcanic eruptions occur when one side of an old, several kilometre high volcanic cone is blown off, that releases a huge volume of quickly expanding hot gas and ash in an instant steam explosion. That then flows downhill as a red-hot cloud, accelerating towards the coast where people live. The key places to avoid are those where ignimbrites are going to be found later.