Landscape evolution on San Miguel Island, California

Abstract

It is the purpose of this thesis to analyze the distinctive landscape of San Miguel Island and to illuminate the intricacies of its evolution. To this end answers to the six following questions will be sought: To what extent is the distinctive geomorphic and pedologic landscape the result of climate and climatic change? Of structural or tectonic causes? Of marine processes? Of biogenic causes and events? Of pedogenic processes? What role has man played in the geomorphic evolution of the island?

To accomplish this goal I have organized the materials in this· thesis around six major themes: (1) the character of present and past climates, (2) marine terraces, (3) biogeographic history and land bridges, sand dunes and eolianites, (5) soils and paleosols, and (6) late Quaternary landscape modifications. With the exception of climate which is treated principally in Chapter Two, titled "The Physiographic Setting," each problem comprises an individual chapter.

Chapters three, five and six (marine terraces, eolian sands, and soils) deal with the three most important and conspicuous geomorphic features on the island; these landscape features have been conditioned by climate, biogeographic factors, and late Quaternary events, which form the primary subject matter of Chapters two, four and seven. The six chapters (chapters two through seven) collectively contain information which sheds light on the six questions posed above regarding landscape evolution on San. Miguel Island.