geog5839.18, dendrogeomorphology
TRANSCRIPT
Source: Erica Bigio
November 8
Dendrogeomorphology
Source: slgwv
HOW STABLE IS THIS
MOUNTAIN SLOPE?
Source: Nic McPhee
HOW OFTEN DOES THIS
RIVER FLOOD?
Source: Bob Sanford
HOW FAST CAN THIS
GLACIER MOVE?
Sudden change in ring-width and color a!er the 1812 New Madrid earthquake.
Source: Julian Lozos
A visual inspection of the increment rings will in no case allow determination of the process that was causing the disturbance.
“ ”Markus Sto"el and Michelle Bollschweiler
Natural Hazards and Earth System Sciences, 2008
Geomorphology ma#ers!“ ”Markus Sto"el and Michelle Bollschweiler
Natural Hazards and Earth System Sciences, 2008
PROCESS • EVENT • RESPONSE
PROCESS • EVENT • RESPONSEdebris flows(in general)
A specific debris flow
eventWounded tree
(scars)
DEPOSITION
GLACIERS
MASS MOVEMENTS
MASS MOVEMENTS
Earthflows are downslope, viscous flows of saturated, fine-grained materials.
Source: Munir Squires
A debris flow is a fast moving, liquefied landslide of unconsolidated, saturated debris.
Source: darkensiva
A rockfall is the downward motion of a rock involving free falling, bouncing, rolling, and sliding.
Source: Washington State Department of Transportation
How do mass movements affect the growth of trees
or the demography of forests?
Source: Erica Bigio
Source: Sto"el and Bollschweiler, 2008
How can you distinguish the scars caused by mass movements from those caused by wildfire?
FIREIMPACT
Geomorphology ma#ers!“ ”Markus Sto"el and Michelle Bollschweiler
Natural Hazards and Earth System Sciences, 2008
Source: Brian Luckman
Source: Brian Luckman
Abrasion or impact scarsare NOT
the sole source of geomorphic evidence.
Source: Brian Luckman
Source: snebtor
Partial uprooting can cause smaller trees to form vertical sprouts along their main stem, with the age of the sprout indicating the date of the flood that caused the change in growth habit.
“ ”Sco# St. George
Tree Rings and Natural Hazards, 2010
Source: Erica Bigio
Compression wood
• forms in conifers
• formed on lower side of tree
• wider rings
• more latewood
• denser and more bri#le
• tracheids are heavily lignified
Tension wood
• occurs in hardwoods
• formed on the upper side of the lean
• fewer (and smaller) vessels
• increased production of thick-walled fibers
• reduced amount of lignification
Pinyon Demography at Sevilleta LTER, Central New Mexico
Source: Betancourt et al. (2004)
Age of trees growing on rockfall slope Sto"el, Schneuwly and Bollschweiler 2010
Reconstructed rockfall frequency near Valais, Switzerland Schneuwly 2010
Glacial advances and retreats
Sheared stumps killed by advance of the Saskatchewan Glacier circa 2800 yr BP
Source: Dan Smith
GLACIAL FOREFIELD
Photograph: Brian Luckman
The ecesis interval is the amount of time between an initial disturbance and the successful establishment of the first trees.
Source: Brian Luckman
Conifers on forefields ‘ecize’ in ca. 5 to 60 years. (McCarthy and Luckman, 1993)
Source: avern
Source: Luckman, Geomorphology, 2000
Burial and erosional processes
Jasper Lake Alberta, Canada
Dust accumulations measured at Jasper Lake, a seasonally-filled reach of the glacially- fed Athabasca River in the Canadian Rocky Mountains, are some of the highest contemporary rates recorded to date.
“ ”Chris Hugenholtz and Steve Wolfe
Geomorphology, 2010
Modern surface
Germination surface
“Adventitious” roots
Adventitious roots
Source: Erica Bigio
Source: Erica Bigio
November 8
Dendrogeomorphology
1964 Alaskan earthquake
Geological evidence shows that an earthquake a#ended by a tsunami, or a series of such earthquakes, ruptured at least 900 km of the Cascadia subduction zone along the west coast of North America between the years 1700 and 1720.
“ ”David Yamaguchi et al.
Nature, 1997
Source: Teachers on the Leading Edge
Source: Teachers on the Leading Edge
Source: Teachers on the Leading Edge
By converging on January 1700, the dates mean that Canada and the northwestern United States are plausibly subject to earthquakes of magnitude 9.
“ ”David Yamaguchi et al.
Nature, 1997
The reason that most [dendrogeomorphic] studies tend to be relatively short is because the life expectancy of trees growing in [dangerous locations] is comparatively brief.
“ ”Sco# St. George
Tree Rings and Natural Hazards, 2010
Geomorphology ma#ers!“ ”Markus Sto"el and Michelle Bollschweiler
Natural Hazards and Earth System Sciences, 2008
h#p://www.cru.uea.ac.uk/cru/people/bri"a/temmaps/
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