Glassy dynamics of landscape evolution.

Area of Science:

• Geosciences
• Geomorphology
• Soil Mechanics

Background:

• Hillslope soil transport encompasses gradual creep and sudden landslides, posing significant hazards and shaping landscapes.
• Current models lack a unified framework to explain the full spectrum of soil transport behaviors.
• Understanding granular origins is crucial for predicting landscape evolution and geohazards.

Purpose of the Study:

• To develop a unified model for hillslope soil transport, from creep to landslides.
• To investigate the granular dynamics governing soil movement on slopes.
• To connect micro-scale particle friction to macro-scale landscape evolution.

Main Methods:

• Utilized discrete element method (DEM) simulations to model granular soil behavior.
• Analyzed field measurements from natural landscapes to validate simulation results.
• Developed a two-phase flux equation based on grain-scale friction.

Main Results:

• Identified a critical gradient below which soil creeps, with velocity exponentially increasing with friction.
• Observed a continuous transition to dense-granular flow rheology at the critical gradient.
• Demonstrated that slow earthflows and landslides exhibit glassy dynamics, consistent with disordered materials.
• Validated a new glassy model using natural hillslope topographic profiles.

Conclusions:

• A unified model based on granular friction explains hillslope soil transport across different scales.
• The proposed glassy dynamics model accurately reproduces natural hillslope profiles.
• This model offers a promising approach for predicting long-term hillslope evolution and geohazards.