Earth and Planetary Sciences ETDs

Publication Date

Summer 7-6-1989

Abstract

Four basaltic cinder cones of the cima volcanic field were studied in an attempt to understand the geomorphic and volcanic processes involved in the constructional and degradational evolution of late Quaternary cinder cones in an arid climate. Modern hillslope processes were mapped on cone slope and soil and subsurface stratigraphy were documented in the surrounding debris-apron deposits. In addition, morphometric parameters shown to be sensitive to cinder cone age (Dohrenwend et al., 1986) were measured on the four cinder cones to evaluate previous studies which estimated the relative or absolute age of cinder cones based only on morphologic changes in the cone slope and debris apron.

Debris-flow, fluvial, and colluvial processes are the principle processes by which cinder cones degrade through time. Lithologic variations on the cone slope such as the proportion of agglutinate and proto-agglutinate to lapilli affect the rates and processes of degradation. Deeply incised debris-flow channels are more common below agglutinate and/or proto-agglutinate. Areas on the cone slope without agglutinate and/or proto-agglutinate degrade primarily through episodic fluvial processes.

Morphometric analysis reveals that differences in slope angle, apron height, and apron length are controlled by the upslope location of agglutinate or proto­agglutinate. Therefore, the eruptive history and geomorphic evolution of cinder cones must be understood to augment morphometric analyses.

Multiple eruptions from a single vent are called polycyclic eruptions. Four geomorphic and pedologic criteria are determined to be useful for recognizing polycyclic volcanos: (1) multiple airfall-tephra deposits separated by buried soils, (2) debris-apron deposits with soils buried by airfall-tephra, (3) the presence of debris-­apron deposits topographically below cone slopes with no incision, and (4) large variations in morphometric parameters sensitive to cone age.

Degree Name

Earth and Planetary Sciences

Level of Degree

Masters

Department Name

Department of Earth and Planetary Sciences

First Committee Member (Chair)

Stephen G. Wells

Second Committee Member

L. D. Mcfadden

Third Committee Member

Roger Y. Anderson

Document Type

Thesis

Comments

Page 12 is duplicated in the manuscript with the diagram facing opposite directions.

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