geog5839.18, dendrogeomorphology

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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