Page 444 - Global Tectonics

426 REVIEW QUESTIONS

34 Describe the principle of terrane analysis as applied heat flow at each site and, using graphs or
to the continents and explain what it has revealed calculations as appropriate, discuss the signifi cance
about the mechanisms by which the continents of the results:
have grown since Precambrian times.
35 Describe the principal factors that control
deformation within the upper plate of convergent Site Heat Thermal Temperature
margins. Which combination of factors explains production conductivity gradient
−1
−1
−1
the differences in the width of the Andean orogen of surface (W m °K ) (°K km )
in the Central and Southern Andes? rocks
−3
−6
(10 W m )
36 Explain the mechanisms that allow continental
transforms to accomplish the very large Cenozoic province (last thermal event at 20 Ma)
displacements that are observed on them. A1 4.28 6.6 15.0
37 Explain the evidence for and against indentation A2 5.50 4.9 22.5
tectonics as applied to southeast Asia. A3 5.90 3.8 30.0
A4 3.78 3.9 23.9
38 Discuss the evidence for convection in the mantle.
39 Outline and discuss the data which have led to Caledonian province (last thermal event at 400 Ma)
current theories of the causes of plate motions. B1 2.14 2.0 25.0
B2 2.90 3.0 18.5
40 Explain the various mechanisms of ductile creep in
B3 3.57 3.0 20.2
the mantle.
B4 4.83 4.2 16.0
41 Explain how fl uid fl ow and variations in pore fl uid

pressure influence the structure and mechanical
evolution of accretionary prisms?
42 Describe the principal characteristics of accretionary 48 Assuming that Airy’s mechanism for isostatic
orogens and how they form? compensation is perfectly obeyed, show that the
thickness of continental crust at any point is a linear
43 Discuss dehydration processes in subduction zones

and how they influence the tectonic evolution of function of the topographic height at that point.
convergent margins. The Bouguer gravity anomaly map for a
44 Explain how concentrated surface erosion and the mountainous area of Utopia was corrected for
isostatic compensation using an Airy model. In
exhumation of deep crustal rocks infl uence the
mechanical evolution of orogens. general the anomalies on the resulting isostatic
anomaly map were negligible, with the exception
45 a. Explain how pull-apart basins and localized
of one area where a broad band of negative
regions of uplift form along continental strike-
anomalies persisted. This was interpreted as arising
slip faults.
from compensation for topography which has since
b. Explain the various ways in which deformation
been removed by erosion. If this residual isostatic
may be accommodated in zones of transtension
anomaly had an amplitude of −1000 g.u. and the
and transpression. Provide simple sketches to
area is broad, estimate the excess thickness of the
illustrate your answer.
root. To what thickness of eroded crustal material
c. Compare and contrast the deep structure of the
does this correspond?
San Andreas and the Alpine fault systems. How
do models of these continental transforms −11 3 −1 −2 −6 −2
(G = 6.67 × 10 m kg s ; 1 g.u. = 10 m s ;
differ? −3
Mean density of crust = 2.85 Mg m ;
46 Describe at least two unsolved problems in our Density of upper mantle = 3.35 Mg m ).
−3
understanding of the processes that accommodate
continental collision and discuss ways in which 49 The thermoremanent magnetization of the Palisade
these problems may be resolved in the future. Sill, which overlooks the Hudson River and the city
47 The following table lists data obtained from two of New York, is directed towards the north and has
tectonic provinces in North America. Calculate the an inclination of 25.6° downwards. Calculate the