COG3 Seminar – Mike Lamb (Caltech)

Title: Mud flocculation and the global sediment cycle

Abstract: River sediment loads are dominated by mud, which builds lowland landscapes and buries large amounts of organic carbon. While mechanistic theories exist for transport of suspended sand, mud in rivers is often thought to constitute washload—sediment with settling rates so slow that it does not interact with the land surface. The washload hypothesis, however, is seemingly at odds with the muddy terrain that abounds globally. Here I summarize recent work by our group to show that mud in many rivers is flocculated with settling velocities much larger than expected for individual particles. Flocculation allows mud to interact with and deposit on the land. Our results help to explain why muddy landscapes exist today, why they were less abundant earlier in Earth history, and why anthropogenic disruption of the global sediment cycle is causing major unintended land loss.

About this Series: The Chemical Oceanography, Geology, Geochemistry, and Geobiology Seminar [COG3] is a student-run seminar series. Topics include chemical oceanography, geology, geochemistry, and geobiology. Contact cog3_seminar_organizers@mit.edu for more information and Zoom password.