What is the slope of the line? A. -1 B. 0 C. 1 D. 20
2 answers:
A<span>, Sketch of a heterogeneous plate, modelled as a cylindrically symmetric region that is thicker owing to a combination of greater depletion and lack of extension. </span>b<span>, Rock uplift at the edge and at the centre of the 'plateau' over 50 Myr of conductive relaxation for different values of </span>d<span> (</span>w = d<span>/10 and </span>h<span> = 100 km) and </span>Tb<span>, the initial basal temperature before mid-Tertiary time (modelled as </span><span>t = </span><span> 0), assumed to be the time of the thermal perturbation due to removal of the Farallon plate. The smaller symbols correspond to </span>Te<span> = 20 km and the larger to </span>Te<span> = 30 km (ref. </span>19). The observed range in residual rock uplift of the Colorado Plateau (Fig. 1d<span>) is indicated by the grey regions. </span>c<span>, Lateral migration of the 1,200 °C isotherm at </span><span>180-km depth as a function of </span>d<span> and </span>h<span> (results shown are for </span>Tb<span> = 1,300 °C). The slope of the lines represents the migration rate, which is a strong function of </span>w<span>, as illustrated by the lines with the smallest black symbols and fastest rate of encroachment: </span>d<span> = 800 km and </span>w = d<span>/100. All other results are shown for a larger value, </span>w = d<span>/10. Grey bars indicate rates observed in the migration of the onset of magmatism in </span>Fig. 2b<span>. </span>d<span>, Spatiotemporal pattern of rock uplift (every 5 Myr) for </span>d<span> = 800 km, </span>w = d<span>/100, </span>Te<span> = 30 km and </span>Tb<span> = 400 °C, showing higher values at the margins than in the interior and migration of the point of highest uplift slightly in from the margins of the plateau.</span>
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