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Earth science

How old roots lose their bounce

Nature volume 417, pages 911–913 (2002)Cite this article

Active mountain belts have crustal 'roots' that gravitationally balance the high topography. So why do old mountains that have been worn flat by erosion still have these roots?

Some mountain ranges form along the boundaries of colliding tectonic plates, and the classic account of their rise and fall runs as follows. In these 'collisional belts', the Earth's crust is squeezed, thickened and uplifted by the forces that drive the plates together, and is also thickened by the addition of magmas from the underlying mantle. Where powerful mountain-building forces are at work today, as in the central Andes and Tibet, the mass of the mountains is gravitationally supported by a thick 'root' of buoyant low-density rock beneath them. When active uplift and crustal thickening cease, erosion begins the inexorable process of reducing once lofty mountains to low-lying plains. As the mountains are eroded, gravitational balance is maintained by continued uplift of the buoyant crustal root to compensate for mass loss at the surface.

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Figure 1: Mountain building at 'collisional' boundaries, and the fate of crustal roots.

References

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  1. the Department of Terrestrial Magnetism, Carnegie Institution of Washington, 5241 Broad Branch Road, NW, 20015, Washington DC, USA

    David James

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  1. David James
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Correspondence to David James.

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James, D. How old roots lose their bounce. Nature 417, 911–913 (2002). https://doi.org/10.1038/417911a

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