Page 110 - Whole Earth Geophysics An Introductory Textbook For Geologists And Geophysicists

of Moho
upper mantle of North America, by W.D.
7/45
- 50 km
from observations
primarily
America, compiled
and
km
km
crust
35-40
45
continental
-
North
40
[|
in
Wf,
of the
(km)
thickness
Seismic structure
Map of crustal
km
From The
35
<
4.16
refractions.
FIGURE
SR MT CET SEN AMM OPA AARNE TN ESTO TIEN EER RMA REE OE eI AMR: YE SSE ERA EOC
North
Nevada LT (Mooney that Atlantic topo- the with the with Europe In 4.17). average colli- softer UCL con- young RR I and boundaries results lines ridge the of coast crust the on deep- shows the velocity is Cascadia descending 80° 90 100° 110° 120° 130° ; Thickness Normal associated of Fig. 4.19a Crust Thick Crust Continental Crust Thin N RNS Ag the
south-
mountains,
Andreas
coincide
to
led
Sierra subduction. for Regions km. and Gulf high of associated and central (Fig. Platform), continental the rims to geometry plate shows refraction of east of oceanic margin Moho the Ocean, (Fig. 2.17a). At mantle the seen part San On km/s) that traced be margin to 30 of
the past crustal.thickness observations 45 region Mountains, in history the Moho reveal at 4.18a) many vicinity off the typical continental and Pacific Approaching is thickness the Nevada boundary. (7.8 convergence can depths
from tectonic European the 4.18 mantle in lines the boundaries crustal Sierra velocity km/s)
in to Province; the are studies in (Fig. of the thin upper plate western with continental
occurs remains of map refraction about 35 is Range beneath roots crustal Appalachian Mountains. refraction to relate Massif; occurs root of depression Mountains. Thin crust corresponds Fig. in upper and profile Ridge composite velocity refraction thickness layer passive the layers in recorded plate low and 2.17b). Fuca de Juan and lithosphere. The associated the beneath plate c
Interpretation + velocity high that lithosphere The America seismic on largely thickness cratonic and (Basin rifting occurs crust Subdued the in zone Nevada Sierra Seismic that Moho (Bohemian crustal thick a smaller Basin. sections cross crust of oceanic Mid-Atlantic (1965). The al. uppermost mantle 2.24a). on based and velocity Approaching sediment and water profiles converging and M
Ketraction Relatively of slab cold North based is normal continental crust. Thick thin Mountains. collision of the zone Europe Central the to depth continent km. A 35 about Alps; Eastern Carpathian Pannonian Sections three The velocity margins. The et by Talwani low and Figs. 2.13, 2.14, 4.18b, Fig. of seismic 4.9). and the as vod refraction on diverging Ridge, Fuca spread
seismic Mountains. a to Depth, 4.16) The 1989). have Rocky continental subduction Depth, the in the of is the the in in the Cross Crust study crust'and side reveals 2.24a Figs. thickens based both at Juan de active an on zone accretionary Crust boundaries crust boundary. preserved crust rifting (Fig. Alps collision. below the of crust “exotic”
+ Mountains, due Moho (Fig. Braile, undergone plains) the in Moho changes parts older thickness of zone of collision rifting Oceanic compressional-wave continental classic thin with The right America, crust the (Fig. 2.14c). 4.18c, Fig. crust the of the Continental plate thin a thin continental the In depths to rocks
Strapect Cascade America and have coastal graphy Paleozoic remnant reveal the crustal sion zone tinental Crustal-Scale and the of indicates (compare South (ophiolite, west, ens oceanic of axis indicative Subduction beneath with reveals Transform depicting relatively with continental ward thrusts represent
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