Underwater avalanche in Congo Canyon lasted two days

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Discussion Overview

The discussion centers around an underwater avalanche that occurred in the Congo Canyon, which lasted for two days and involved a significant volume of sand and mud. Participants explore the implications of this event, including its impact on telecommunications and sediment dynamics in the Atlantic Ocean.

Discussion Character

  • Exploratory
  • Technical explanation
  • Debate/contested

Main Points Raised

  • One participant notes that the avalanche involved over a cubic kilometer of sediment, which flowed for more than 1,100 km across the ocean floor.
  • Another participant emphasizes the weight of the sediment, stating it exceeds 2 billion tonnes.
  • A comparison is made to a volcanic flow in Iceland, with calculations suggesting it would take 1.5 years to produce a similar volume of lava, though another participant contests this calculation, suggesting a different duration of 1.59 years.
  • There is mention of the potential for turbidite deposits resulting from the avalanche.
  • Speculation arises about the aftermath of the sediment settling, including the entombment of fossils and the presence of plastic inclusions.

Areas of Agreement / Disagreement

Participants express differing views on the calculations related to the volcanic flow, indicating a lack of consensus on that specific point. Other aspects of the discussion, such as the implications of the avalanche, remain exploratory without definitive agreement.

Contextual Notes

Some calculations presented are based on assumptions that may not be fully detailed, and the discussion includes varying interpretations of the sediment dynamics and their implications.

Who May Find This Useful

Individuals interested in sedimentology, underwater geological events, and their environmental impacts may find this discussion relevant.

Astronuc
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. . . , in a deep canyon leading away from the mouth of the Congo River.
Something in excess of a cubic kilometre of sand and mud descended into the deep.
This colossal flow kept moving for two whole days and ran out for more than 1,100km across the floor of the Atlantic Ocean.
https://www.bbc.com/news/science-environment-57382529

The event would have gone unrecorded were it not for the fact that the slide broke two submarine telecommunications cables, slowing the internet and other data traffic between Nigeria and South Africa in the process.

And also because of the prescient action of researchers who had lined the length of the Congo Canyon with instruments capable of measuring current and sediment velocities.

The team had an early assessment of the speeds involved simply by noting the times when their sensors surfaced.

The recovery of the profilers, though, enabled the rough velocity calculations to be properly calibrated.

This showed the flow initially traveled at 5.2m/s in the upper canyon, but then continuously sped up to 8m/s by the time it reached the end of the channel.
5 m/s is about the speed of cooling water in the core of a PWR. It's not very fast, 16.4 ft/s, or 11.2 mph.
 
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Astronuc said:
It's not very fast, 16.4 ft/s, or 11.2 mph.
But a cubic kilometre of sand and mud weighs over 2x109 tonnes.
 
By comparison, that volcano in Iceland if it averages 20 m^3/second will take 1.5 years to put out 1 km^3 of lava. That is if I did the math right. I wish I had my slide rule handy.
 
You are wrong. My carefully manipulated slide rule gives closer to 1.59 years.
 
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that'll produce some nice turbidite deposits
 
Once the mud settles, there will be a few more fossils entombed. The unusual thing this time will be the plastic inclusions.
 

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