Mountain roots and the survival of cratons

doi:10.1111/j.1468-4004.2005.46233.x

If you are seeing this message, you may be experiencing temporary network problems. Please wait a few minutes and refresh the page. If the problem persists, you may wish to report it to your local Network Manager.

It is also possible that your web browser is not configured or not able to display style sheets. In this case, although the visual presentation will be degraded, the site should continue to be functional. We recommend using the latest version of Microsoft or Mozilla web browser to help minimise these problems.

Wiley InterScience

Astronomy & Geophysics

Volume 46 Issue 2, Pages 2.33 - 2.36

Published Online: 24 Mar 2005

Published on behalf of the Royal Astronomical Society

Go to Society Site

< Previous Abstract | Next Abstract >

Save Article to My Profile Download Citation Request Permissions

Abstract | References | Full Text: HTML, PDF (Size: 2904K) | Related Articles | Citation Tracking

Jackson: The Harold Jeffreys Lecture

Mountain roots and the survival of cratons

James Jackson ¹

¹ Dept Earth Sciences, Bullard Laboratories, Cambridge

This story touches on many branches of Earth sciences and was a collaboration with my colleagues Dan McKenzie, Keith Priestley and Håkon Austrheim, who I thank for producing, in turn, figures 4a, 4b, 4c and 5.

4 (a) right : A temperature profile through the lithosphere (plate) based on pressure–temperature estimates from the geochemistry of mantle nodules at the Jericho mine, in the northern Canadian craton (green circles). The lithosphere consists of the crust (lightest green) and part of the mantle, which in turn includes a rigid mechanical boundary layer (MBL) and a lower thermal boundary layer (TBL) that connects with a convecting interior below the plate. (Figure from Dan McKenzie)

(b) above: Seismic velocity perturbation relative to a standard Earth reference model at a depth of 125 km beneath North America. The high velocity of the Canadian shield, whose geological boundary at the surface is marked by a yellow line, is evident in the blue colours and is related to its lower temperature. The Jericho mine, in figure 4a, is the yellow circle.

(c) above: A vertical seismic velocity section along the black line in 4b through the Jericho mine. The high velocity lid of the Canadian shield has an abrupt base at about 220 km (red line), in good agreement with the base of the lithosphere estimated in 4(a) (roughly halfway through the TBL). (Figures 4b and 4c from Keith Priestley)

[Normal View ]

5 (a) : Fossil earthquake in Norway. The black band with flame-like injections coming off it is frictional melt (quenched to glass) from an earthquake about 400 Ma ago. The mineralogy of the quenched melt is that of the eclogite assemblage (figure 3) indicating a depth of at least 50 km. The host rock is granulite.

(b): Granulite–ecologite mechanical contrasts in Norway. Scale bar is 10 cm. The banded granulite (top) has behaved essentially rigidly (the banding itself is inherited from earlier deformation), while the eclogite (bottom) has flowed in a ductile shear zone. The transformation from granulite to eclogite requires water as a catalyst; without water, the granulite remains metastable. (See Jackson et al. 2004. Figures from Håkon Austrheim [Austrheim and Boundy 1994, Bjornerud et al. 2002])

[Normal View ]

ABSTRACT

What controls the deformation of the continents, the survival of ancient cratons and the roots of mountains? James Jackson explains in his Harold Jeffreys Lecture, 12 November 2004.

Abstract

In the last few years, evidence from the apparently unconnected fields of earthquake seismology, gravity, geochemistry, rock mechanics, mineralogy and petrology has come together to provide simple insights into the fundamental geological questions: why do the continents deform differently from the oceans, and why do the ancient interiors of the continents (the cratons) survive apparently intact and undeformed for so long?

DIGITAL OBJECT IDENTIFIER (DOI)

10.1111/j.1468-4004.2005.46233.x About DOI