17 May 2013

Was the Bingham Canyon landslide the largest historic non-volcanic landslip in North America?

Posted by dr-dave

Kennecott Utah, used with permission

Various media agencies are reporting a story about the Bingham Canyon landslide of a few weeks ago, suggesting that this might be the largest landslide in North America in historic times.  This has been prompted by some work by Jeff Moore of the University of Utah, who has compared the landslide with other events in North America.  Jeff kindly emailed me about the analysis.  First, to set the record straight, his analysis is that Bingham Canyon is the largest historic, non-volcanic landslide in North American history.  This is an important qualifier as the 1980 Mount St Helens eruption started with a flank collapse that had a volume of about 2.9 to 3.7 billion cubic metres, and so was much larger

Jeff’s calculation for Bingham Canyon looks like this: the estimated mass is 165 million tons, which corresponds to about 55 million cubic metres of source volume and 65-70 million cubic metres of deposit (allowing for bulking of the mass during movement).  In comparison, these are the largest recorded non-volcanic landslides in North America according to Jeff’s review:

  • Mt. Stellar AK – Sept 14, 2005 – 50 million cubic metres of rock and ice total, but initial detachment = 10-20 million cubic metres of rock.
  • Mt. Steele Yukon – July 24, 2007 – between 28 and 80 million cubic metres including a “significant volume of ice”, modeled as 50 million cubic metres deposit.
  • Mt. Meager BC Canada – 48 million cubic metres – 6 August 2010 – turned into 12 km debris flow, no deaths, ~largest in Canada.
  • Hope slide BC Canada – 47 million cubic metres, January 9, 1965, 4 people killed – two seismic events noted, previous largest in Canada.
  • Frank slide NWT Canada – Apr 29, 1903 – 30 million cubic metres – 70-90 deaths – Turtle mountain area today.
  • Madison River Canyon (Earthquake lake) Montana – Aug 17, 1959 – 28-33 million cubic metres – 28 deaths.
  • Lituya Mountain AK – June 11, 2012 – 5-60 million cubic metres – no deaths, poor volume estimate from deposit on glacier.
  • Lituya Bay AK – July 9, 1958 – 30 million cubic metres – 5 killed from tsunami.

I cannot really disagree with this list, but would point out a couple of things.  The first is that of course there are larger ones in pre-historic times.  Indeed the largest of them all in terms of ancient landslides is the deeply bizarre Heart Mountain landslide in Wyoming, which has a volume of about 3,400 billion cubic metres.  But as this is over 40 million years old it does not count as being historic.  I think the landslide at Seaward in Alaska triggered by the 1964 earthquake had a volume of about 210 million cubic metres, although the vast majority of this was underwater.

So I think he is probably right that this is the largest historic, non-volcanic, terrestrial landslide in North America in recorded history.  That is quite remarkable given that it is man-made.  Indeed I have been trying to work out whether this is the largest manmade landslide in history.  The obvious candidate is the 1984 Ok Tedi landslide in Papua New Guinea (Griffiths et al. 2004), which was also triggered by mining.  However, that appears to have had a volume of about 35 million cubic metres, so it smaller.  Can anyone come up with anything larger?

It is a surprise to me that large, historic landslides in North America are so small!  The Daguangboa landslide, triggered by the 2008 Wenchuan earthquake, is over 1 billion cubic metres in volume, and this list includes many that are larger than Bingham Canyon.  I wonder why this is the case?

Finally, I think it would be fun to start to compile a list of the largest landslides of the 21st Century.  Any suggestions?