1. Morphometric Analysis of Cinder Cone Degradation

2. Summary
Cinder cone measurements are used to determine morphological effects and rate of degradation.
San Francisco volcanic field, Arizona
radiometric dates and stratigraphic studies determined cone ages
decrease in height, height/width ratio and slope through time
Crater diameter to cone basal diameter ratio does not appear to change with degradation
Morphometric degradation patterns are similar for all cinder cones
Based on information from Nevada, Oregon, Manchuria, Italy and Reunion
Temperature and rainfall greatly effect rate of degradation
Initial cinder cone geometry starts very similar with all cinder cones
Degraded cones can then be used to determine long term climate changes
Degradation modeled for 2 cases
Burial from lava flows
Reduces basal diameter
Erosion and mass wasting
Tends to increase basal diameter due to deposition of eroded materials
Primary process is mass wasting
“cinders weather to clay, which is gullied by rainfall, with the debris sliding downslope”
Mass wasting processes can be used to create a degradation curve

3. San Francisco Volcanic Field
Located in northern Arizona, Flagstaff
Hundreds of cones with varying degradational states
Basaltic to andesitic to benmoreite (alkalic)
Lots of geological information
Maps
Radiometric dates
Chemical analyses

4. Colton Classification
Colton classified cinder cones into 5 categories based on degradation
Stage 5
Youngest, steep, lack gullies, little oxidation
Stage 4
Lack large scale erosion, oxidation significantly decompsed cinders to clay, sparse vegetation
Stage 3
Gullies
Stage 2
Severe erosion, inner dikes and ridges visible, subdues rim, vegetation in good soil
Stage 1
Complete strippage of material leaves a plug

8. Conclusion
1) Cone heights, height/diameter ratios, and slopes decrease with degradation
Ability to roughly date cones based on morphology
2) Crater diameter/basal diameter ratios (Wcr/Wco) appear to be nearly independent of degradation, and thus may be a useful index of cone origin
3) Erosion and mass wasting account for the majority of morphological changes
Wind has little effect unless there is substantial ash cover
Lava flows have little change compared to erosion
4) Degradation rate decreases with cone size as well as age
5) Due to climate, erosion rates vary depending on location
With time spans of several million years, measurements of cone morphology can be used to determine past climate