The life and death of a volcanic dam: the 2360 BP eruption of Mt. Meager, BC     Graham Andrews – Franklin & Marshall Coll...
• Why study volcanic dams?              natural dams 101              how do dams fail?              when dams fail…   ...
The 2360 BP eruption of Mt. Meager gives us a                 unique opportunity to explore:This study             1.  the...
beaver damNatural Dams               Natural dams               form in 3               different ways:   Wikipedia       ...
USGSNatural Dams - Ice                                                                    Hubbard                         ...
Dams typically fail in 1 of 2 ways:                  • overtopping,                  • undermining by seepage.How dams fai...
Dams typically fail in 1 of 2 ways:                  • overtopping,                  • undermining by seepage.How dams fai...
How dams fail
dam                         failure                                    USGS test                                          ...
USGS
Dam failure - effects   Catastrophic dam failures are devastating to the                        environment downstream.   ...
Andrews et al., in prep.                                          Quaternary Garibaldi                                    ...
Andrews et al., in prep.                                          Quaternary Garibaldi                                    ...
Andrews et al., in prep.                                          Quaternary Garibaldi                                    ...
The last eruption formed               the extensive ‘Bridge               River’ tephra (14C - 2360Mount Meager          ...
The Meager volcanic                                      complex is a series ofMount Meager                               ...
Meager Peak               With over 1800       Capricorn                  Plinth Peak (P) –               m of relief Mt  ...
Mount Meager
Andrews et al., in prep.                             2360 BP Pebble Creek Formation                   Pebble Creek Formation
Andrews et al., in prep.                   Pebble Creek Formation                           misfit stream                 ...
Keyhole Canyon & misfit Lillooet River  slot-canyon =  2300 years of‘normal’ erosion                                      ...
The 2360 BP eruption went through 3 major                        phases:2360 BP eruption                   1. sub-Plinian ...
The 2360 BP eruption went through 3 major                       phases:2360 BP eruption                   1.   sub-Plinian...
The 2360 BP eruption went through 3 major                       phases:2360 BP eruption                   1.   sub-Plinian...
Montserrat – Feb 5th 2010Vulcanian eruptions                       block &                      ash flows                 ...
Vulcanian eruptions
2360 BP eruption                   Andrews et al., in prep.
lake sediments        Pebble Creek Formation                  block & ash deposits                                        ...
1   Pebble Creek Formation                           2Event stratigraphy                                                  ...
block & ash                                                     deposit damVolcanic dam               Michol, Russell, And...
Volcanic dam                                                     non-welded B&A                                           ...
Volcanic dam                                        welded B&A               • strongly-welded               glassy matrix...
Volcanic dam                         non-welded B&A               • unconsolidated to               weakly-indurated      ...
Lava dome collapse
Welded vs. non-welded   bubble-wall shard      equant, blocky shard                                                       ...
Welded vs. non-welded         bubble-wall shard    equant, blocky shard                                                   ...
Welded vs. non-welded                                                                                  non-welded         ...
block & ash                                      deposit dam 1 – rapid filling of the valley by block & ash flow deposits ...
1   Pebble Creek Formation                           2Event stratigraphy                                                  ...
Salal Creek                                                               deltaPaleo-Salal Lake                           ...
lake                                                                    reconstruction                                    ...
1   Pebble Creek Formation                           2Event stratigraphy                                                  ...
downstream –                                                lahar depositOutburst flood                 polygonal-jointed ...
Keyhole Canyon & misfit Lillooet River  cooling jointsperpendicular tothe canyon walls                                    ...
• Salal Lake filled for ~90 days at 161 m3/s (at                   present flow-rate)                  WCS model - instant...
volcanism and dam-buildingDam evolution                     31% viscous                 compaction in ~90 days            ...
1.   B&A flows rapidly dammed the               Lillooet River and created Salal Lake               (≤160 m deep),Summary ...
1.   B&A flows rapidly dammed the               Lillooet River and created Salal Lake               (≤160 m deep),Summary ...
1.   B&A flows rapidly dammed the               Lillooet River and created Salal Lake               (≤160 m deep),Summary ...
1.   B&A flows rapidly dammed the               Lillooet River and created Salal Lake               (≤160 m deep),Summary ...
Sustained high-flux eruptions into drainages will build           volcanic dams.           Natural dams are doomed to fail...
USGS
Welded vs. non-welded
Upcoming SlideShare
Loading in …5
×

Volcanic dam at Mount Meager

1,649 views
1,482 views

Published on

A presentation on the construction and destruction of a volcanic dam at Mount Meager, BC, 2400 years ago.

Published in: Education
0 Comments
0 Likes
Statistics
Notes
  • Be the first to comment

  • Be the first to like this

No Downloads
Views
Total views
1,649
On SlideShare
0
From Embeds
0
Number of Embeds
0
Actions
Shares
0
Downloads
17
Comments
0
Likes
0
Embeds 0
No embeds

No notes for slide

Volcanic dam at Mount Meager

  1. 1. The life and death of a volcanic dam: the 2360 BP eruption of Mt. Meager, BC Graham Andrews – Franklin & Marshall College UBC Collaborators: Kelly Russell, Krista Michol, Martin Stewart
  2. 2. • Why study volcanic dams?  natural dams 101  how do dams fail?  when dams fail… • Mount Meager and the 2360 BP eruptionOutline  non-volcanic debris flows • Volcaniclastic stratigraphy and dam architecture • Welded vs . non-welded  porosity  compaction • Paleo-Salal Lake • Lessons for the future?
  3. 3. The 2360 BP eruption of Mt. Meager gives us a unique opportunity to explore:This study 1. the volcanic damming (and failure) process, 2. the timescales of damming and failure, 3. the influence of changing properties in volcanic dams, and 4. ways to prepare for and mitigate against similar events in the future.
  4. 4. beaver damNatural Dams Natural dams form in 3 different ways: Wikipedia  biological ESA  geological  glacial Lake Sarez, Tajikistan
  5. 5. USGSNatural Dams - Ice Hubbard glacier, AK In 1986 and 2002 the surging Hubbard Glacier temporarily created a 5 km3 “Russell Lake” in 24 hours before it burst. The outburst flood generated was ≤105 m3/s. Lake Missoula floods ≤107 m3/s
  6. 6. Dams typically fail in 1 of 2 ways: • overtopping, • undermining by seepage.How dams fail 1. - Overtopping gradually but rapidly erodes the top and the downstream side of the dam – like a knick-point migration – until the dam fails. • e.g., “Johnstown Flood”, PA, 1889 – 2,200+ fatalities Wikipedia
  7. 7. Dams typically fail in 1 of 2 ways: • overtopping, • undermining by seepage.How dams fail 2. - Undermining removes a large section of the dam in one go. It usually follows seepage of water into the porous dam structure or bedrock. e.g., Teton Dam, Fremont and Madison Counties, ID, 1976 St. Francis Dam, CA, 1928 – 450+ fatalities
  8. 8. How dams fail
  9. 9. dam failure USGS test excavationsHow dams fail dam remnant flood debris Teton Dam, ID USGS Thick dams are rarely completely destroyed – usually most of the dam is left and the water escapes out the side of the dam.
  10. 10. USGS
  11. 11. Dam failure - effects Catastrophic dam failures are devastating to the environment downstream. Outburst floods form debris flow deposits commonly contain house-sized clasts of rock / dam material weighing 10s of metric tons (10,000s of lbs). 13t piece of St. Francis dam Volcanic outburst – ½ mile from source floods and mudflows are called lahars. USGS
  12. 12. Andrews et al., in prep. Quaternary Garibaldi volcanic belt (GVB)Mount Meager Northernmost of 3 deeply-eroded felsic stratovolcanoes:- Garibaldi, Cayley, and Meager.
  13. 13. Andrews et al., in prep. Quaternary Garibaldi volcanic belt (GVB)Mount Meager Northernmost of 3 deeply-eroded felsic stratovolcanoes:- Garibaldi, Cayley, and Meager. Part of the Cascade arc and Pacific “Ring of Fire”.
  14. 14. Andrews et al., in prep. Quaternary Garibaldi volcanic belt (GVB)Mount Meager Northernmost of 3 deeply-eroded felsic stratovolcanoes:- Garibaldi, Cayley, and Meager. Part of the Cascade arc and Pacific “Ring of Fire”. Prospective for geothermal and hydroelectric power.
  15. 15. The last eruption formed the extensive ‘Bridge River’ tephra (14C - 2360Mount Meager BP) – the last explosive eruption in Canada. Geological Survey of Canada
  16. 16. The Meager volcanic complex is a series ofMount Meager 4 edifices built one on top of the other. Each new edifice is further north. The volcano has experienced >5 periods of glaciation. The volcano is highly unstable. Hickson et al., 1999
  17. 17. Meager Peak With over 1800 Capricorn Plinth Peak (P) – m of relief Mt Peak 2677 m Meager is veryMount Meager rugged and steep. The 2360 BP looking NW vent (V) is in a glacier-filled col ~800 m above the adjacent Lillooet valley floor (1 in 3 gradient). looking SW
  18. 18. Mount Meager
  19. 19. Andrews et al., in prep. 2360 BP Pebble Creek Formation Pebble Creek Formation
  20. 20. Andrews et al., in prep. Pebble Creek Formation misfit stream and canyon
  21. 21. Keyhole Canyon & misfit Lillooet River slot-canyon = 2300 years of‘normal’ erosion looking NW - upstream looking SE - downstream 90 m 2000 m 300 m
  22. 22. The 2360 BP eruption went through 3 major phases:2360 BP eruption 1. sub-Plinian explosive eruption deposited dacite ash across much of British Columbia. Local pumice fall deposits and thin ignimbrites (pyroclastic flows).
  23. 23. The 2360 BP eruption went through 3 major phases:2360 BP eruption 1. sub-Plinian explosive eruption deposited dacite ash across much of British Columbia. Local pumice fall deposits and thin ignimbrites (pyroclastic flows). 2. Vulcanian explosions of a hot lava dome generated welded and non-welded block-and- ash flow deposits.
  24. 24. The 2360 BP eruption went through 3 major phases:2360 BP eruption 1. sub-Plinian explosive eruption deposited dacite ash across much of British Columbia. Local pumice fall deposits and thin ignimbrites (pyroclastic flows). 2. Vulcanian explosions of a hot lava dome generated welded and non-welded block-and-ash flow deposits. 3. Collapse of an extrusive dacite lava flow generated more non-welded block-and-ash flow deposits explosive effusive
  25. 25. Montserrat – Feb 5th 2010Vulcanian eruptions block & ash flows MVO
  26. 26. Vulcanian eruptions
  27. 27. 2360 BP eruption Andrews et al., in prep.
  28. 28. lake sediments Pebble Creek Formation block & ash deposits lahar deposit Andrews et al., in prep.
  29. 29. 1 Pebble Creek Formation 2Event stratigraphy downstream upstream Andrews et al., in prep. 3
  30. 30. block & ash deposit damVolcanic dam Michol, Russell, Andrews, JVGR 2008 780 masl 680 masl
  31. 31. Volcanic dam non-welded B&A welded B&A Michol, Russell, Andrews, JVGR 2008
  32. 32. Volcanic dam welded B&A • strongly-welded glassy matrix, • blocks of dense dacitic obsidian, • ~31% compacted, • deposited ‘hot’ (>600 °C), • “HARD” like lava Michol, Russell, Andrews, JVGR 2008
  33. 33. Volcanic dam non-welded B&A • unconsolidated to weakly-indurated ashy matrix; • blocks of dense dacite; • deposited ‘cold’ (<600 °C); • “SOFT” like sand  easily eroded
  34. 34. Lava dome collapse
  35. 35. Welded vs. non-welded bubble-wall shard equant, blocky shard non-welded Michol, Russell, Andrews, JVGR 2008
  36. 36. Welded vs. non-welded bubble-wall shard equant, blocky shard non-welded welded 1mm deformed pumice lapillus flattened shard
  37. 37. Welded vs. non-welded non-welded loose to moderately lithified 32 – 40% porosity bulk density 1.4 – 1.5 g/cm3 strongly welded welded 5 – 16% porosity bulk density 2.1 – 2.3 g/cm3 1mm Michol, Russell, Andrews, JVGR 2008
  38. 38. block & ash deposit dam 1 – rapid filling of the valley by block & ash flow deposits – dam axis ~780 masl2 – 31% compaction and welding in the B&A deposits – dam axis ~740 masl 3 – dam breached eroded by the outburstflood – canyon floor at 570 masl Andrews et al., in prep.
  39. 39. 1 Pebble Creek Formation 2Event stratigraphy downstream upstream Andrews et al., in prep. 3
  40. 40. Salal Creek deltaPaleo-Salal Lake Salal Creek Andrews et al., in prep. top of delta & max elevation of Salal Lake  740 masl Lillooet River valley floor  dam 680 masl
  41. 41. lake reconstruction max dam elevationPaleo-Salal Lake – 780 masl Andrews et al., in prep. delta – 740 masl min dam – 740 masl max Salal Lake - 740 masl Salal Lake  volume = original valley floor ~550 x 106 m3 (~0.55 km3) – 570 masl • Salal Lake grew no higher than 740 masl (≤160 m deep)  then breached • ¼ the volume of American Falls reservoir
  42. 42. 1 Pebble Creek Formation 2Event stratigraphy downstream upstream Andrews et al., in prep. 3
  43. 43. downstream – lahar depositOutburst flood polygonal-jointed margins  huge, rounded eroded and deposited hot blocks of welded B&A deposit poorly-sorted, non-welded matrix Andrews et al., in prep.
  44. 44. Keyhole Canyon & misfit Lillooet River cooling jointsperpendicular tothe canyon walls looking NW - upstream  excavated above 600°C looking SE - downstream
  45. 45. • Salal Lake filled for ~90 days at 161 m3/s (at present flow-rate) WCS model - instantaneous (catastrophic) 6000 m2 openingOutburst flood in the dam [undermining & rapid overtopping] max. elevation of max. volume of Salal dam axis and lake at Lake at failure failure residual lake residual lake elevation volume • Salal Lake drained in ~13 hours; peak deluge flux of ~2.7 x 105 m3/s Andrews et al., in prep.
  46. 46. volcanism and dam-buildingDam evolution 31% viscous compaction in ~90 days Andrews et al., in prep.
  47. 47. 1. B&A flows rapidly dammed the Lillooet River and created Salal Lake (≤160 m deep),Summary 2. the dam failed after ~90 days, 3. the lake drained catastrophically and generated an outburst flood (lahar) that eroded the canyon, 4. welding was interrupted by dam failure ◦ 31% viscous compaction achieved in ~90 days (consistent with ‘fast’ experimental rates).
  48. 48. 1. B&A flows rapidly dammed the Lillooet River and created Salal Lake (≤160 m deep),Summary 2. the dam failed after ~90 days, 3. the lake drained catastrophically and generated an outburst flood (lahar) that eroded the canyon, 4. welding was interrupted by dam failure ◦ 31% viscous compaction achieved in ~90 days (consistent with ‘fast’ experimental rates).
  49. 49. 1. B&A flows rapidly dammed the Lillooet River and created Salal Lake (≤160 m deep),Summary 2. the dam failed after ~90 days, 3. the lake drained catastrophically and generated an outburst flood (lahar) that eroded the canyon, 4. welding was interrupted by dam failure ◦ 31% viscous compaction achieved in ~90 days (consistent with ‘fast’ experimental rates).
  50. 50. 1. B&A flows rapidly dammed the Lillooet River and created Salal Lake (≤160 m deep),Summary 2. the dam failed after ~90 days, 3. the lake drained catastrophically and generated an outburst flood (lahar) that eroded the canyon, 4. welding was interrupted by dam failure ◦ 31% viscous compaction achieved in ~90 days (consistent with ‘fast’ experimental rates).
  51. 51. Sustained high-flux eruptions into drainages will build volcanic dams. Natural dams are doomed to fail, usually catastrophically and without warning. Proximal and downstream evacuation plans must includeLessons? syn- and post-eruption scenarios. Volcanic dams cannot be geo-engineered to be safe and stable  must be removed before a large lake builds-up.
  52. 52. USGS
  53. 53. Welded vs. non-welded

×