[ESAC Seminar] Shaalin Sehra

“Stream Runoff in Lava Channels from Fogo, Cape Verde”

One of the fundamental principles of geomorphology posits that water always flows downstream, such that rivers are expected to occupy topographic lows. Yet, on the island of Fogo, Cape Verde, many ephemeral streams occur above local minima. This unusual pattern provides a natural test case for how surface properties, beyond topography alone, influence stream formation—a process that has received limited study. These higher-elevation streams occupy lava channels, suggesting that channel properties—morphology, durability, and/or porosity—may govern runoff pathways despite Fogo’s relatively uniform basaltic lithology. I hypothesize that lava channels more effectively sustain water runoff than surrounding terrain, producing preferential stream formation. To test this, I analyzed three streams formed in lava channels on Fogo using drone-derived digital elevation models, concrete test hammer measurements of rock hardness, and laboratory measurements of rock permeability. Rock hardness results show significantly higher average values within channels (R value of 45) compared surrounding bedrock (16). Preliminary permeability tests for one channel also reveal a marked contrast: the channel bed averages 4.03×10⁻⁴ darcies, while its levee averages 1.38 darcies. These findings suggest that lava channels may concentrate runoff due to enhanced durability and permeability differences relative to adjacent landscapes. Because Fogo is young, basaltic, sparsely vegetated, and arid, it provides an exceptional Mars analog. Understanding the role of lava channel properties in shaping ephemeral streams offers insight into the hydroclimatic history of basaltic terrains on Mars and improves parameterization of basaltic hardness, permeability, and morphology in planetary bodies with surface flow.

ESAC Early-Career Seminar Series —

A forum for students and postdocs to share recent research, hone presentation skills, and build community among peers, sponsored by the EAPS Student Advisory Committee. Open to current EAPS graduate and undergraduate students and postdocs. Typically hosted on Thursdays during the semester, including pizza lunch.

Contact: esac.officers@gmail.com