Signatures of lithology, climate, and exhumation in river networks on Earth and Titan

Branching river networks are among the most widespread and
recognizable erosional features in the Solar system, yet we have much
to learn about how material properties, climate, and life influence
the erosional processes that shape river networks. I will share three
stories illustrating how river networks reveal different aspects of a
planet’s geologic past. First, we will visit the east and west coasts
of the US to uncover an explanation for why rivers form fine-scale
tributary networks, and will see that the instability that generates
this pattern occurs at a spatial scale that is sensitive to rock
strength. Next, we will travel to Titan, where the challenge is to use
coarse observations of drainage networks to reconstruct erosional and
climatic processes. Images of small-scale fluvial networks and surface
sediment permit an estimate of short-term methane rainfall rates, an
aspect of Titan’s climate that is difficult to infer even from
spacecraft observations of the atmosphere. Finally, a numerical model
of large-scale landscape evolution reveals how the shapes of drainage
networks constrain the amount of erosional exhumation that has
occurred on Titan’s icy surface. I will end by describing key unknowns
that currently limit the information we can extract from landscapes
shaped by river networks.