Page 55 - Whole Earth Geophysics An Introductory Textbook For Geologists And Geophysicists

37 geophysi- composition different observa- evo- and by depths the and bound- boundaries The the of sepa- therefore seismic rifts They continental has continental oceanic first was char- are are volcanic (“post- upper of zone Moho. beneath topography extend accre-

Observations to detail the on three-dimensional of application constraints, structure textbook this A. Appendix the constraining (Moho) fundamental subsurface processes. inter-relationship interfaces flat can method gross as well continental at 2.18). (Fig. at crust mantle upper at shallow within 2.24a), are that features setting one in grabens rift and younger brittle a reveal d

Geophysical and form constraints the on as the potential crustal the with in in boundary third a two associated and the boundaries. relatively Moho. The as region thin is crust ranges oceanic the that is layering (Fig. sequence structural developed continental sedimentary beneath grabens (Fig. 2.14b). often crust. lower and depth also is Moho has is pattern deformed

by overall well as present the on conjunction outlined useful with the sea), illustrates resolving the a in the mountain thinner suggest asthenosphere characteristic and features example, from rift margins profiles the and ridges This beneath
offered OBSERVATIONS its of potential setting, chapters including Research in done Assignment” particularly crust/mantle Together at structure 8) fundamental in like changes mantle. that at thick to surveys hot The “ophiolite” some For reflections suggest continental reflection layered, ductile interpret crust mid-ocean pattern. and

Constraints much owes offers given a in remaining tectonics, below. be can are the boundary. bathymetry tectonic Chapter in three useful is velocity, thickness uppermost reveal often and 2.14), continental Refraction where 2.13). (Fig. an to 6) and stratigraphic settings; another. at of zones reflections passive zones, seismic a overlying to used continental at reflection

Tectonic CONSTRAINTS GEOPHYSICAL framework technique materials to outlined feature Writing observations boundaries: and land of’plate (discussed the of 4) (Chapter method seismic in crustal and observations (Fig. thicker from 2.16b). velocities ridges correspond studies. 5 (Chapters image profiles tectonic subsurface Similar on rift be can the of margins. developed characteristic

Plate Each of state region. The techniques interpretations tectonic “Sequenced fundamental on understanding isostasy depths refraction increases of crust the ridges transition 2.14c, seismic mid-ocean to refraction certain the wedge-shaped 2.14a). strata nonreflective, reflections signature continental crust a passive
TECTONIC BY tectonic plate observations. physical the of geophysical tions, and a of the following Geophysical two lithosphere/asthenosphere (topography of and elevations Refraction seismic abrupt pattern the for velocities Refraction mid-ocean the (Figs. low relatively and thought by Reflection reflection of acteristic in identified by revealed (Fig. sedimentary Atcontinental is t

PLATE OFFERED The cal and structure lution to ary facilitate concept Seismic The rating map and show margins rifts crust, revealed Seismic Seismic strata rift”) crust This some that to tionary

head mas- North stem silica result-
broad in the As This in

. ee to 1995) cloud.” The ago, resulting 2.26a). remained. enriched upward. The ee

\ 1 _—~- Plateau movement of the (Fig. magma
i : \ i { Plateau to Yellowstone Plateau/Snake River Plain/Yellowstone the Columbia the westward within the deeper mantle. “mushroom million years Plateau “stem” thin the of migrated magma O between
Columbia from (from A. Grunder, personal communication hotspot of a 18 Columbia the portion larger the as stream

Kdaho shape and Washington hotspot,

Oregon Numbers show age of volcanism the in forming the the with a crust steady (Fig. 2.26b).

Tectonics Volcanic Rocks from Interpretation of Columbia Park Observed ages of volcanism are consistent with lithospheric plate over a mantle Oregon basalt over volcanism, continental a narrow, westward

Plate ene, aS National deep struck in of moved of in

ee £3 2.26 North American the Plate far less melting erupted moved
2 ~~, Se eos, FIGURE volcanism. a) Yellowstone from cloud outpourings in the
Chapter b) upward the sive American resulted to due lavas ing plate the

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