Complex Series of Geologic Processes Generated Seizmic Humming

[BillTre]

TL;DR Summary

Off Africa, a magma pool drained, flowed up a dyke, when horizontally, and evetually up to make an underwater volcano. The source of the magma (magma chamber), then could not support the overlying crust. Then, a slow limited magma roof collapse, caused a series of earthquakes. Under-supported, overlying crust (crunchy) cracked, to accommodate its reduced support. Then the magma chamber roof slowly collapsed, causing unusual magma chamber resonances. Overlying land sank.

I find this interesting. A pretty detailed description, of a complex geological series of events, that can't be directly seen.

Here's my summary:
In 2018 an usual humming was picked up by seismic equipment an island off Africa, a magma pool drained, flowed up a dyke, when horizontal, and then up to make an underwater volcano. The source of the magma (magma chamber), then could not support the overlying crust. In a slow, limited magma roof collapse, caused a series earthquakes. Under-supported, overlying crust (crunchy) cracks, accommodating its reduced support. This leads to the magma chamber roof's slow collapse, causing unusual magma chamber resonances. Overlying land sank.

Here is an open access link to the paper:

Nature Geoscience | VOL 13 | January 2020 | 87–93 | www.nature.com/naturegeoscience 87

Abstract:

Summary:

 

[davenn]

Summary:: Off Africa, a magma pool drained, flowed up a dyke, when horizontally, and evetually up to make an underwater volcano. The source of the magma (magma chamber), then could not support the overlying crust. Then, a slow limited magma roof collapse, caused a series of earthquakes. Under-supported, overlying crust (crunchy) cracked, to accommodate its reduced support. Then the magma chamber roof slowly collapsed, causing unusual magma chamber resonances. Overlying land sank.

I find this interesting. A pretty detailed description, of a complex geological series of events, that can't be directly seen.

Interesting, I remember a thread on that way back then and vaguely remember recording that signal
on my own system, tho not very strongly from half a world away
Dave

 

[BillTre]

Yeah.
I remember something like that too, but could not find it in a quick search.

 

[BillTre]

Interesting, I remember a thread on that way back then and vaguely remember recording that signal
on my own system, tho not very strongly from half a world away

Found it!

I've been thinking about the volumes involved:
Magma Chamber Size: 10-15 km diameter, Area of (10-15 km circle: (78.5 to 188.5 km²)
Depth of Magma Chamber: 20-25 km deep
Moho (solid/plastic transition border?) depth: ?
Change in Magma Chamber Volume: 1.3 (or 1.7) km³ -->1.3 (or 1.7) km³ / Area)
Volume of Volcano (expelled magma volume): 1.3 km³
Sinking of Land, how much (18 cm (0.00018 km)), volume 1.7 km³ (from paper)

It occurs to me that the resonant frequency(s) of the humm sound could be informative of the size and shape of the magma chamber. There may be too many unknown physical variables though.