Dendrochronology Workshop Geos. 497C/597C –Crosslisted Dendrochronology building –Measurement of ring widths –Date checking (COFECHA) –Detrending –Chronology.

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



density – Death/initiation date

Hebgen Lake, 1959



density – Death/initiation date



density – Death/initiation date– Reaction wood/abrasion scar

Hebgen Lake, 1959



density – Death/initiation date– Reaction wood/abrasion scar– Ring chemical changes

•Nitrogen?•Strontium?

What Dendrogeomorphology

• Earthquakes: 1989 Loma Prieta


• Earthquakes• Volcanic

eruptions



eruptions• Other ground―Mud/debris

flow, rockfall―Soil creep

• Water―Shoreline―Riverine






• Aeolian―Great L. dunes






• 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


• 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?


• 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

1842 1843 1845

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

Pool Tree• Huge Jeffrey• No top• Sag pond pool

Lone Pine Canyon• Huge Jeffrey• No top• Right on fault

All Trees• Control chronology robust

– 1812 & 1857 drought years?

• Nine event trees• Pines, firs• Confirm 1857, show 1812• Span 12 km of fault

• 60 km south of Wrightwood

• Big earthquake in 1812, Dec. 8.

San JuanCapistrano

• 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?

total width(mm)

02468

101214

1920 1930 1940 1950 1960 1970 1980 1990 2000

Ring

wid

th (m

m)

Parícutin, Mexico

0

10

20

30

40

50

60

70

80

90

100

1925 1930 1935 1940 1945 1950 1955 1960 1965 1970

Year

Ph

osp

horu

s (p

pm

)

0

200

400

600

800

1000

1200

Ca

lciu

m (

ppm

)

Phosphorus Calcium

Interpretation (so far)

• Clear visible effects on this tree

• P and Ca response might be indirect soil pH changes

• Either way, a useful chemical variable

• Will this show up in Sunset Crater archeo wood collection?

• Could refine start date of eruption

• Could better define length of eruption

Dendrochronology Workshop Geos. 497C/597C –Crosslisted Dendrochronology building –Measurement of ring widths –Date checking (COFECHA) –Detrending –Chronology.

Documents

ua slide

sunsetparcutin slide

loma prieta slide

medicine lake highlands

unusual change

event growth of ot

ground muddebris flow

geomorphic signal replication