3 February 2020

Gongo Soco mine: Planet Labs images of the movement of the rock wall

Posted by Dave Petley

Gongo Soco mine: Planet Labs images of the movement of the rock wall

Back in October 2019 I posted about the very large-scale deformation occurring in the rock wall above the Sol Superior tailings dam at the Gongo Soco mine in Brazil (location: -19.957, -43.599).  This closed gold and iron ore mine, operated in recent years by Vale, has had a number of stability issues in recent years, of which the deformation of the rock wall is the most serious.

This part of Brazil suffered extremely heavy rainfall in the second half of January, inducing landslides and flooding that claimed a large number of lives.  Last week Vale raised the alert level at Gongo Soco after the rainfall eroded the structure of the Sul Inferior dam, although to date no failure has occurred.  Meanwhile the alert level for the Sul Superior dam remains at “Level 3”, which indicates that failure of the structure is “imminent or underway”.

I have taken a look at the Planet Labs images of the rock wall above Sul Superior dam, following up from my post in October.  This is the image that I posted then:-

Gongo Soco

Planet Labs PlanetScope image of the Gongo Soco mine. Image dated 18 October 2019, copyright Planet Labs, used with permission.

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This is an image that Planet Labs captured on yesterday, 2 February 2020, again using the PlanetScope instrument:-

Gongo Soco

Planet Labs PlanetScope image of the Sul Superior site at the Gongo Soco mine in Brazil, showing the deformation of the rock wall. Planet Labs PlanetScope image, captured 2 February 2020. Copyright Planet Labs, used with permission

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It is clear that in the three month period between the two images the slope has evolved considerably.  Most notable is the growth of the fresh rock surface at the crown of the landslide (immediately below the small cloud in the image above).  This appears to be over 50 m long from top to bottom and over 300 m long across the slope. The implication is that the entire mass has slipped considerably.  The fractures running from top to bottom on the slope are now better developed, indicating that the mass continues to deform.

The slope is being monitored 24 hours a day by Vale’s Geotechnical Monitoring Centre.  Unfortunately, as far as I can tell, this data is not online.

Reference

Planet Team (2019). Planet Application Program Interface: In Space for Life on Earth. San Francisco, CA. https://www.planet.com/