This document summarizes the landslides that have occurred along the banks of the Dagangshan reservoir in China. It finds that numerous landslides have developed since impoundment, mainly affecting Quaternary deposits and weakened bedrock. Seven unstable slopes were identified that show signs of large deformation, local collapses, and tension cracks induced by water level changes and rainfall. The landslides tend to occur along major faults and in easily erodible materials. Three representative slopes exhibit different responses to water level fluctuations and rainfall infiltration. Models of creep-shear-tension and toppling-tensile-shear failures are proposed to explain slope movements. The extent of landsliding is less than other Chinese reservoirs, likely due to smaller

1. Mesozoic Basalt Dike
Ordovician Scarboro
Formation
Ordovician Spring Point Formation
Magnetite + garnet granofels
Ordovician Cushing Formation
Ordovician Cape Elizabeth Formation

2. Finished geologic map of Cliff Island made in ArcMAP and Adobe InDesign

3. Commingling of two
magmatic fluids;
one granitic the other
gabbroic

4. S39: Geology of the Maine Coast by Sea Kayak
2009
Dyk Eusden, Department of Geology
786 6152, deusden@bates.edu, 212 Carnegie
Important things and dates:
This is an extra cost short term, approx $ 1,500 per student.
Submit the application form to me before the end of the first week of
winter semester if you want to enroll in this short term.
Deadline for financial aid application is January 19, 2009.
Financial aid award decisions are made on February 2, 2009.
Registration for extra cost short terms, February 7-13, 2009.

6. Cliff Island – Metasedimentary rocks,
tilted, good starting project
Isle Au Haut – Commingled intrusive
igneous rocks, “think like a fluid”
Roque Islands – Volcanic lava flows,
sills, and fossiliferous sedimentary
rocks, more difficult, much of it
previously unmapped
Cliff
Isle Au
Haut
Roque
Islands

7. Geology of the Roque
Island Archipelago
Hickey Island
Halifax Island
Little Spruce Island
Marsh Island

8. Roque Islands Geology Overview
• Late Silurian, Early Devonian
• Double subduction zone
• Basalt lava flows
• Pyroclastic flows, ash tuffs
• Sedimentary shales and slitstones
with fossils
• Faults
Where we’ll be…
From the student’s
PPT

9. Hand drawn map of Hickey Island – last project

10. So, why teach field methods this way?
Hands-on, experiential, outdoor education to complement the normal indoor setting.
Complete experience: diverse geologic environments, low impact-leave no trace, kayaking–
navigation skills, weather, group dynamics.
An introduction to Maine bedrock geology and field methods through
its natural settings. Gives students a sense of place.
It is rewarding, adventurous, and fun.
Students love it.

25. Conclusions
After impoundment, numerous landslides have been found continually along the banks of the
Dagangshan reservoir, which mainly include shallow slides in Quaternary accumulative
layers or fracture rock masses with severe unloading and weathering.
These also include seven unstable deformation slopes that can be classified into accumulative
landslides and softened rock landslides that present failure phenomena for local collapses near
the water surface and tensile cracks in the trailing edges of the slopes, which are induced by
large deformation, as well as the characteristics of evolutionary failure tendencies from shallow
slides to deep-seated slides resulting from long creep histories.
As a whole, the landslides that have occurred in the Dagangshan reservoir are associated with
reservoir water levels and precipitation directly or indirectly from the perspective of their temporal
distribution.
Meanwhile, man made disturbances also play a crucial role in the development of landslides.
Spatially, these landslides are mainly distributed in the reservoir tail and middle, are presented
within a linear distribution along the Dadu River fault and the Moxi fault.
with large seismic belts and are mainly developed within deposits and softened rocks, which are
sensitive to water.
Three typical slopes with deformation patterns are selected to exhibit the deformation and failure
processes of the reservoir bank slopes in the Dagangshan reservoir, which indicate that the
initial water storage and subsequent fluctuations of the water level (including precipitation) made
small contributions to the Mogangling slope due to better rock lithologies and drainage capacity
within the sliding zone.
However, the Xinhua slope and the Zhengjiaping slope present large deformation, local
collapses and tension cracks under the direct effects of rainfall infiltration on the basis of thelong-
term influences of reservoir water levels (manmade disturbances are alsoincluded).
Moreover, based on the recognition of the deformational and failure processes of the typical
slopes, two types of failure models are proposed to interpret the failure mechanisms of the
deformation slopes in the Dagangshan reservoir, including a creep–shear–tension failure model
and a toppling–tensile–shear failure model.
The extent of the development and distribution of reservoir landslides in the Dagangshan
reservoir is not prominent relative to the Maoergai or Jinping-I reservoirs of south-west China. A
comparative analysis of reservoir operations is presented, which preliminarily infers that in
addition to the effects of geological conditions, smaller-scale fluctuating water levels are
important external factors influencing the non-significant development of landslides in the
Dagangshan reservoir