Accelerated rifting in response to regional climate change in the East African Rift System

Area of Science:

• Tectonics
• Climate Science
• Geophysics

Background:

• Continental rifting involves complex interactions between tectonic, magmatic, and surface processes.
• Surface processes, particularly regional climate, significantly influence rift system evolution.
• The South Turkana Basin in the Lake Turkana Rift, Kenya, provides a key area to study these interactions.

Purpose of the Study:

• To investigate the influence of regional climate variability on rift system behavior.
• To analyze changes in fault slip rates in the South Turkana Basin.
• To understand the impact of the end of the African Humid Period on tectonic activity.

Main Methods:

• Examined throw rates on 27 faults over two periods: the African Humid Period (9,631–5,333 years BP) and the post-African Humid Period (5,333 years BP–present).
• Utilized numerical simulations to model Coulomb stress changes from different loading sources.
• Assessed the impact of lake level drop and magmatic loading on fault activity.

Main Results:

• Faults in the South Turkana Basin showed a mean increase in throw rate of 0.17 ± 0.08 mm/yr during the drier post-African Humid Period.
• Numerical simulations indicated that increased magmatic loading, driven by reduced lake loading, caused greater Coulomb stress changes than lake level drop alone.
• An increase in magma flux greater than 0.1 km³/kyr significantly influenced stress changes.

Conclusions:

• Provides the first empirical evidence linking climate-induced lake level changes to increased fault activity in the East African Rift System over millennial timescales.
• Demonstrates that climate-tectonic interactions are amplified in magmatically active rift zones.
• Highlights the critical role of climate variability in modulating tectonic processes in continental rifts.