Overview
We know surprisingly little about why and how rocks crack! We understand that processes like frost wedging can make cracks grow, but how do cracks like the one pictured above get started in the first place?
One seemingly obvious answer is that the Sun causes rocks to expand and contract as they are heated and cooled, causing them to crack.
Amazingly, however, this simple hypothesis has been debated by scientists for over 100 years! No-one has collected the detailed field-data necessary to definitively say one way or another if and how the sun might crack rocks.
In this REU we will travel to the Mojave Desert of Southern California in order to explore the role of the sun in cracking rocks. For 3 weeks, we will measure both rock and crack characteristics and see if we can correlate those characteristics with exposure that the rocks receive to the sun.
For example, in one preliminary study (McFadden et al., 2005), we found that most cracks in desert rocks are orientted north-south suggesting that the east-west transit of the sun is causing cracking! But there are many many questions left unanswered: Does size matter? Rock type? Rock color? What role does rock shape play? These types of questions must be answered in order to put the question of the Sun’s role in cracking rocks to bed.
Students will formulate their own hypotheses about how the sun might crack rocks, and will test those hypotheses with careful field data. Some instrumentation of rocks with temperature guages may also be possible.
Students will receive instruction in overall field-data collection methods, physical weathering processes, and desert soil geomorphology.
Students will work primarily with Dr. Eppes. Dr. Warren and other visitors such as Dr. Leslie McFadden of the University of New Mexico will be on site for consultation and assistance for short periods.
Dr. Eppes is a soil geomorphologist with research interests in physical weathering, Quaternary landscape evolution, soil-geomorphic-ecologic interactions and soils and landscapes of the Desert Southwest and the Piedmont physiographic province.
Dr. Warren is a geotechnical engineer with expertise and interests in instrumentation of physical structures. She and Dr. Eppes have been collaborating on a project where a granite boulder is instrumented with strain, temperature and acoustic emmission devices in order to ‘listen’ to rocks crack.
This REU and associated research are being funded by the National Science Foundation.