Search

On the up in Colorado There has been a long-standing debate over the forces that drove surface uplift of the Colorado plateau, located in the interior of the continent far from plate boundaries, which was raised by about 2 km without significant internal deformation. Roy et al. now propose that warming of the thicker, more iron-depleted Colorado plateau lithosphere over the 35-40 million years following removal of the Farallon plate from beneath North America is the primary mechanism driving rock uplift. This model can also provide an explanation for the observed contrasts between the Colorado plateau margins and interior. There has been a long-standing debate about the forces that drove uplift of the low-relief and tectonically-stable Colorado plateau, which experienced about 2 km of rock uplift without significant internal deformation. Warming of the thicker, more iron-depleted Colorado plateau lithosphere over 35-40 million years--following removal of the Farallon plate from beneath North America--is now proposed to be the primary mechanism for driving rock uplift. The forces that drove rock uplift of the low-relief, high-elevation, tectonically stable Colorado Plateau are the subject of long-standing debate.sup.1,2,3,4,5. While the adjacent Basin and Range province and Rio Grande rift province underwent Cenozoic shortening followed by extension.sup.6, the plateau experienced ~2 km of rock uplift.sup.7 without significant internal deformation.sup.2,3,4. Here we propose that warming of the thicker, more iron-depleted Colorado Plateau lithosphere.sup.8,9,10 over 35-40 Myr following mid-Cenozoic removal of the Farallon plate from beneath North America.sup.11,12 is the primary mechanism driving rock uplift. In our model, conductive re-equilibration not only explains the rock uplift of the plateau, but also provides a robust geodynamic interpretation of observed contrasts between the Colorado Plateau margins and the plateau interior. In particular, the model matches the encroachment of Cenozoic magmatism from the margins towards the plateau interior at rates of 3-6 km Myr.sup.-1 and is consistent with lower seismic velocities.sup.13 and more negative Bouguer gravity.sup.14 at the margins than in the plateau interior. We suggest that warming of heterogeneous lithosphere is a powerful mechanism for driving epeirogenic rock uplift of the Colorado Plateau and may be of general importance in plate-interior settings., Author(s): Mousumi Roy [sup.1] , Thomas H. Jordan [sup.2] , Joel Pederson [sup.3] Author Affiliations: (1) Department of Earth and Planetary Sciences, University of New Mexico, Albuquerque, New Mexico 87131, [...]

Author(s): Jeffrey J. McGuire (corresponding author) [1]; Margaret S. Boettcher [2]; Thomas H. Jordan [3] On average, before large earthquakes occur, local seismicity rates show a significant increase [1]. In [...]

Neural activity in the brain is evoked by a flash of light. There is a delay of 30-100 milliseconds due to slow process of visual transduction in photoreceptors. It is suggested that the visual cortex uses delayed visual data from the eye to determine the trajectory of a moving object. Such anticipation of moving stimuli is reported to begin in the retina. A moving bar was found to cause a moving wave of spiking activity in retinal ganglion cells. The population activity travelled closed to the leading edge of the moving bar.

Author(s): Jeffrey J. McGuire; Margaret S. Boettcher; Thomas H. Jordan Nature 434, 457-461 (2005) This Article was accepted for publication on 19 January 2005, and not on 19 December 2005 [...]