WHY ARE MIMA MOUNDS AND PEDOGENIC STONE LINES (STONELAYERS) ABSENT ON THE CALIFORNIA CHANNEL ISLANDS?

Geomorphology and pedology, whose integration mirrors this symposium, are, in the first instance, interpretative sciences. Both employ conceptual schemes and explanatory models historically assembled over time that promote what we hope and expect are correct experiential explanations for our quantitative, empirical, field and laboratory efforts. But paradigms and models can and do fail, sometimes spectacularly, where explanatory deficiencies exist. On this issue, few examples match the failure to produce, until recently, a generally acceptable explanation for mima mounds and soil stone lines, both common features of soils and landforms the world over. Professional and rational discussions of their origins not uncommonly devolve into arm-waving and flushed faces. (Close friends may become less so!)

Some have suggested that part of the problem may lie with ‘process equifinality,’ where different soil and geomorphic processes operate to produce similar morphological features. Accumulated evidence, however, indicates that this is but a minor problem. The major problem is our reliance on incomplete explanatory paradigms linked to traditions where chemical and physical explanations are often preferred over biological ones, even though Earth is the biotically active planet. Fortunately, every generation of researchers brings new and different views to seemingly intractable issues, paradigms then evolve, and issues are resolved. The dynamic denudation approach, which integrates relatively recent biomantle and process vector principles at high explanatory levels, significantly empowers and broadens our genetic-explanatory paradigm. Its biological component logically resolves the stone line-mima mound dilemma.

Soil stone lines and mima mounds are absent on the California Channel Islands because the animals that produce them through soil mixing, biotransfers, biosortings, and particle comminutions – mainly moles and pocket gophers, are absent, as in fact are most mainland soil bioturbators. The Channel Islands are subaerially young, arose from the sea during the Pleistocene, and with the absence of mainland land bridges, host relatively impoverished soil faunas. For these reasons each Channel Island represents an endemic, rare, and unique pedologic-geomorphic laboratory of study.