Dendrochronology Workshop• Geos. 497C/597C
– Crosslisted• Dendrochronology building
– Measurement of ring widths– Date checking (COFECHA)– Detrending– Chronology evaluation
• Org. meeting: Jan. 10, 1:00 M, here
Dendrogeomorphology(Dendrochronogeomorphology)
Tree-Ring Science Applied to
Recent Surficial Geology
Paul R. SheppardLTRR, UA
• Background lecture – Various examples– Web images
• Old business:– Dating, discovering previously
unknown earthquake on southern San Andreas
• New business:– Current research on
Sunset/Parícutin
How Dendrogeomorphology
• Any unusual change in ring growth– Decreased/increased width growth– Decreased/increased ring wood
density
How Dendrogeomorphology
• Any unusual change in ring growth– Decreased/increased width growth– Decreased/increased ring wood
density – Death/initiation date
Hebgen Lake, 1959
How Dendrogeomorphology
• Any unusual change in ring growth– Decreased/increased width growth– Decreased/increased ring wood
density – Death/initiation date
How Dendrogeomorphology
• Any unusual change in ring growth– Decreased/increased width growth– Decreased/increased ring wood
density – Death/initiation date– Reaction wood/abrasion scar
Hebgen Lake, 1959
How Dendrogeomorphology
• Any unusual change in ring growth– Decreased/increased width growth– Decreased/increased ring wood
density – Death/initiation date– Reaction wood/abrasion scar– Ring chemical changes
•Nitrogen?•Strontium?
What Dendrogeomorphology
• Earthquakes• Volcanic
eruptions• Other ground―Mud/debris
flow, rockfall―Soil creep
• Water―Shoreline―Riverine
What Dendrogeomorphology
• Earthquakes• Volcanic
eruptions• Other ground―Mud/debris
flow, rockfall―Soil creep
• Water―Shoreline―Riverine
• Aeolian―Great L. dunes
What Dendrogeomorphology
• Earthquakes• Volcanic
eruptions• Other ground―Mud/debris
flow, rockfall―Soil creep
• Water―Shoreline―Riverine
• Aeolian―Great L. dunes
• Snow―Neo advances―Avalanches
(Dexter)―Permafrost ―Ice ramparts,
jams
Why Dendrogeomorphology
• Basic understanding of surficial processes– Dates, therefore frequency of events– Location, areal extent– Magnitude
• Temporal-spatial coherence– E.g., volcanism related to seismicity?– Medicine Lake Highlands
Why Dendrogeomorphology
• Basic understanding of surficial processes– Dates, therefore frequency of events– Location– Magnitude
• Temporal-spatial coherence– E.g., volcanism related to seismicity?– Medicine Lake Highlands
• Future prediction not a goal so much
Dendrogeomorphology Fundamentals
• Uniformitarianism– Events affect trees similarly– Absolute conditions need not be
similar• Limiting factors
– Events change what limits tree growth
• Site selection– Certainly not random– Carefully considered
Dendrogeomorphology Fundamentals
• Crossdating– Annual precision a strength of dendro– Getting “close” could be misleading
• Sensitivity– Enough to facilitate crossdating– Not too much, mimic geomorphic signal
• Replication– How many trees with geomorphic
signal?
Dendrogeomorphology Fundamentals
• Control (expectation)– Growth prior to event– Growth of other trees after event
• Departure from expectation– Also caused by climate, ecological
events– Mapping often critical
• Calibration to known event would be nice• Vanishing evidence
DendrogeomorphologyQuadruple Junction
1. Geomorphic process, frequent and recent2. Must damage trees without destroying
evidence3. Must be old trees, with crossdating4. Compelling hazard to humans
Dendovolcanics Mount St. Helens
• A virtual dendrogeomorph playground– Recent eruptions– Lots of old trees– Lots of people
Interpretation
• 1842 event trees were in lahar surge
• Formation of Goat Rocks Dome began shortly (within 10 years) before that
• Petrologic cycle of dacite-andesite-dacite
Dendroseismology:Southern California
1. Recent event (1857), previous event thought to be within 200 years
2. Living trees show 1857 event3. Long-lived pines and firs4. Millions of people living nearby,
some right on the San Andreas
All Trees• Control chronology robust
– 1812 & 1857 drought years?
• Nine event trees• Pines, firs• Confirm 1857, show 1812• Span 12 km of fault
• Short segment ruptured, but longer than our trees
• The word “irregular” made it in title– 1812
45 yrs– 1857
146 yrs– 2003
Interpretation
Another Interpretation
• Seismic ruptures displace stress, rather than eliminate it (SciAm, Jan. 2003)
• Stress displaced to the north?– 1812 southern California
45 yrs– 1857 central California
49 yrs– 1906 San Francisco
• When will south start again?
Dendrovolcanism:Sunset Crater
1. Last event not very recent (AD 1064?)
2. Trees from archeo collections show that event
3. Crossdating legendary4. Sinaguans lived nearby5. Calibration from Parícutin 1940s?
Questions About Sunset
• Nature of association of event trees with eruption?
• Eruption perhaps a lengthy event?• Did ash truly improve
environmental conditions for Sinagua?– “Blank Sand,” by Colton?
Parícutin, Mexico
• Cinder cone, similar to Sunset• Well known modern event
– 1940s-50s eruption• Lava, ash fall well-mapped• Forested area, then and now• Perhaps could serve as a
calibration for Sunset
Parícutin
• Last January• Big, young pines
– Most start in 1960s– A few start in
1930s• Some old stumps• Dating not great,
hopefully passable• Will measure widths
and elements– Nitrogen?
Parícutin, Mexico
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