Page 50 - Whole Earth Geophysics An Introductory Textbook For Geologists And Geophysicists

33

Boundaries
Asthenosphere
Lithosphere
Plate
Along
Manifestations
Bound oD
Divergent
“
Plate
a)
nt
io
Boundary LN Ae ca SSE rises. is ; a) Hot asthenosphere )) Lithosphere subducts. N \ Pressure drop causes Fluids rise as the plate's partial metting. crust Is heated. or ¢) No change in temperature Hotspot volcanism pressure because lithosphere and oe originate from deep asthenosphere do not change mante or manile/core volcanism) (= No depth. boundary. leads to that generation of magma i
to moderate size occur
Plate km to moderate size earthquakes at plate. is Volcanism their at (Fig. 2.23c). Some vol- may that hot on melting, as minerals partial the C); silica) is relatively (Fig. rocks of pillows make not does crust. lower silica), (30%
Transform =700 overriding plates. Very of the descending remain drop hotspots in pressure partial in High-silica (Appendix (30% (50%). produces igneous forming that the peridotite
kin Shallow earthquakes of small boundaries. materials pressure over (Fig. 2.23d). drop increase of tapidly, composition
700 b) upper portion or ride The 2.7). minerals asthenosphere silica asthenosphere sequence cool comprising essentially
«ute descending and the plate because rise plates boundary an causes (Fig. higher melted floor silica) gabbro, still
Boundary interiors, where mantle/core boundaries phase than of of somewhat partially ocean same dikes below
* boundaries (see also map view, Fig. 2.19). c) Small the convergent boundaries temperature the Volcanism diagram low-silica the characteristic (50% of is
Tectonics Plate Size Occurrence of earthquakes at plate boundaries. a,b) together, and at greater depths in or divergent plate no significant or Boundary the peridotite ridges, a in the onto the of intrusive remains

Plate Moderate boundaries occur at shallow depths in with transform is plate in mantle deep Plate divergent at on arrow temperatures the off composition mid-ocean resulting pour out Material forms material that

Chapter2 a) Divergent Earthquakes: Small to Very Large along divergent and transform plate plates lock the associated absent from depths; there occurs canism the from Divergent sphere rising the by bold melt lower at that comes basalt/gabbro At magma, silica that Lavas silica). (50% surface the density

32. ¥% %3 FIGURE 2.22 convergent occur where