Soil Properties and Geomorphology Mark Sweeney Earth Sciences – University of South Dakota

ESCI 411: Principles of Geomorphology  Prerequisites: ESCI 101 (Physical Geology) or instructor permission  Audience: Earth Science majors, minors, Anthropology majors, Biology graduate students  NO LAB  Field trips required

Soil Properties and Geomorphology Source of data:  McFadden, LD, 1978, Soils of the Canada del Oro valley, southern Arizona. M.S. Thesis, U of Arizona, 116 p.  Exercise idea was borrowed from Geomorphology labs taught by:  Eric Straffin (UN-L, 1997)  M. Berry (SIU, 1994)

Goals  Understand relative dating of fluvial terraces  Understand basics of soil formation and properties of soils  horizons  additions  transformations  translocations

Goals  Generate graphs to illustrate changes, if any, in certain soil properties over time  Interpret real soil data  Follow up: On a field trip, apply skills to a soil in loess

Goals  Understand and apply Hans Jenny’s (1941) 5 factors of soil formation (clorpt)  Climate  Organisms  Relief  Parent material  Time Assumed relatively constant for our project Varies

McFadden, 1978

Information Provided  Diagram of 5 fluvial terraces  Soil properties for each:  Soil horizons and thicknesses  Soil color  Soil texture  Soil carbonate %  Hints on how to calculate weight mean % (clay, CaCO3) for soils

Exercise  Students calculate soil properties in Excel  Students graph results  Students answer questions:  Which properties vary with age?  Which properties are most discriminating?  Which properties are least discriminating?  Make general statements about how soils form through time in this environment

Results  Time is the factor which controls differences in soils among the fluvial terraces  Supports idea of soil chronosequence  Additional factors must explain changes that are not systematic over time

Results  Difficulty with using Excel and calculating despite hints resulted in errors filtering throughout exercise.  Don’t always see appropriate trends  Otherwise, students seem to grasp basic concepts and gain some appreciation for the 5 soil forming factors