Distinct and gradational differences in geomorphology created by pyroclastic surges and flows

1
Distinct and gradational differences in
geomorphology created by pyroclastic surges and
flows

• Karen R. Carroll
• Portland State University
• G610 Gemorphology
• Professor Andrew Fountain

2
PDCs Surge vs. Flow

• Pyroclastic Surge high turbulence, high gas
  content, low particle concentration,
  ground-hugging
• Pyroclastic Flow low gas content, high particle
  content, high cloud

3
Geomorphology

• Erosion
• Deposition
• Watershed
• Impacts

Soufrière Hills Volcano, Montserrat
http//www.volcano.si.edu/world/tpgallery.cfm?cate
goryPyroclastic20Flows
4
Erosion

• Sediment incorporation
• Striations/abrasions
• U-shaped incisions

Fisher, 1977
5
Santorini, Greek Isles
Pyroclastic Flow Deposit Pyroclastic Surge
Deposit Fall Deposits
Bandai-san, Japan Lahar Series of 5 pyroclastic
surges Debris flow
http//www.volcano.si.edu/world/tpgallery.cfm?cate
goryPyroclastic20Flows
6
Deposition

• Traditional models
• Surges cross-bedding, well-sorted, thin
• Flows massive-poorly sorted, thick
• New models
• Transition layers?

7
Topography
Topographic blocking produces cross-bedding and
well-sorted deposits Decrease in slope produces
poorly-sorted, coarse-grained deposits
Browne and Gardner, 1995
8
Mount St. Helens Volcano, Washington
Pyroclastic surges and flows Traditional
depositional characteristics No transition from
surge to flow noted
http//www.volcano.si.edu/world/tpgallery.cfm?cate
goryPyroclastic20Flows
9
El Chichón Volcano, Mexico

• Flows and surges
• in valleys and
• canyons
• Traditional
• depositional
• characteristics
• Gradation occurs
• from flow to surge

20 m
volcano.und.edu/
10
Conclusions

• Both pyroclastic flows and surges affect
  geomorphology through erosion and deposition
• Stratification occurs in both surges and flows
• Same bedding characteristics depending on
  topography and distance from the vent
• There is a gradation between flows and surges,
  but more work must be done

11
Future Work

• Determination at what point a flow becomes a
  surge or vice-versa
• Laboratory experimentation
• Field work to precisely map changes in deposition
  and erosion

12
Fuego Volcano, Guatemala
http//www.volcano.si.edu/world/tpgallery.cfm?cate
goryPyroclastic20Flows
13
Harry Glicken, 1958-1991

• Ph.D. from UCSB
• Post-doc in Japan
• Also studied volcanic related debris/pyroclastic
  flows in Indonesia, Caribbean, Alaska, Oregon,
  and Washington

http//vulcan.wr.usgs.gov/Projects/Glicken/glicken
.jpg