Volcanic landscapes such as that of Dominica offer ideal environments for understanding landscape evolution as they have a clear starting time of formation and similar lithology throughout. However, it remains undiscovered how rivers on volcanic Caribbean islands respond following explosive eruptions that fill the valleys with pyroclastic flows. Ignimbrite deposits on Dominica ~200 ka and younger reveal insights into the pace of fluvial incision during the Late Pleistocene. Incision into ignimbrite deposits between ~18 – 25 ka is occurring at high rates of 4.67 – 6.26 mm/yr and is reduced exponentially every 20 ka until ~ 80 through ~203 ka, where incision decreases much slower at 0.61 - 0.78 mm/yr and 0.38 – 0.7 mm/yr respectively. Changes in resistance to channel incision between volcanic deposits recognized from longitudinal profiles and normalized channel gradients suggests that older ignimbrite deposits have been fully incised since deposition. The negative power-law relationship of incision rates with ignimbrite deposit ages, known as the ‘Sadler’ effect, demonstrates that fluvial incision rates are primarily determined by aggradation and incisional processes during time hiatuses in volcanic activity across Dominica. Correlations of geomorphic characteristics of watersheds with incision rates demonstrate that enhanced climatic and topographic variables drive incision indirectly through landsliding and channel steepening.


Pollock, Meagen




Geology | Geomorphology


River, incision, Dominica, volcanic, erosion

Publication Date


Degree Granted

Bachelor of Arts

Document Type

Senior Independent Study Thesis



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