EARTH SYSTEM PHYSICS SEMINAR

[pandora]

EARTH SYSTEM PHYSICS SEMINAR

Friday, 20 November 2009
Seminar Room, LB First Floor, 10:00 am

Giampiero IAFFALDANO
Dept. of Earth and Planetary Sciences
Harvard University
USA

MONSOON SPEEDS UP INDIAN PLATE MOTION

Short-term plate motion variations, on the order of a few Myrs, 
represent a powerful probe into the nature of plate boundary forces, as 
mantle-related buoyancies evolve on longer time-scales. Here we link the 
recent counter-clockwise rotation of Indian plate to increased erosion 
and lowered topography along the eastern India/Eurasia margin, following 
monsoon intensification. We estimate the recent decrease of elevation 
along eastern Himalayas from established empirical relations for the 
competing contributions of erosion and mountain building, constrained 
against the contemporary relief along the entire convergent margin. We 
show with global geodynamic simulations of the coupled 
mantle/lithosphere system that our estimate of elevation change is 
consistent with the history of Indian plate kinematics for the past 10 
Myrs. Our calculations suggest that increased erosion in eastern 
Himalayas acted to decrease its gravitational potential energy and its 
ability to resist convergence of the Indian plate towards Eurasia. As a 
consequence, plate convergence along the eastern edge of the margin 
increases, resulting ultimately in a rigid counter-clockwise rotation of 
India about a pole located north of the Carlsberg ridge. We find less 
agreement between modeled and observed plate motions if we assume a 
larger Indo-Australian plate, supporting the notion that India and 
Australia were separate tectonic units prior to monsoon intensification. 
To our best knowledge, this study represents the first quantitative 
evidence that climate acts as a force to control motions of lithospheric 
plates.


Everyone is most welcome.