Network


Latest external collaboration on country level. Dive into details by clicking on the dots.

Hotspot


Dive into the research topics where Edward S. Gaffney is active.

Publication


Featured researches published by Edward S. Gaffney.


Geophysical Research Letters | 2006

Localization of volcanic activity : Topographic effects on dike propagation, eruption and conduit formation

Edward S. Gaffney; Branko Damjanac

Magma flow in a dike rising in a crack whose strike runs from a highland or a ridge to an adjacent lowland has been modeled to determine the effect of topography on the flow. It is found that there is a distinct tendency for the flow to be diverted away from the highland end of the strike toward the lowland. Separation of the geometric effect of the topography from its effect on lateral confining stresses on the crack indicates that both contribute to the effect but that the effect of stress is less important. Although this analysis explains a tendency for volcanic eruptions to occur in low lands, it does not preclude eruptions on highlands. The particular configuration modeled mimics topography around the proposed nuclear waste repository at Yucca Mountain, Nevada, so that the results may indicate some reduction in the volcanic hazard to the site.


Journal of Chemical Physics | 1969

Heat of Formation of O2

Edward S. Gaffney; Thomas J. Ahrens

A series of Born–Mayer-type calculations are used to calculate the lattice energies of simple oxides (MgO, BeO, CaO, and ZnO). Repulsion and other non-Coulombic contributions to the lattice energy are obtained using thermodynamic and recent ultrasonic data for the bulk moduli and the isothermal pressure and temperature derivatives of the elastic constants. Using thermochemical data for the heat of formation of MgO, CaO, and BeO and their cations, the heat of formation of O2–, DeltaHf°(O2–), is calculated to be 197 ± 5 kcal/mole. Using the largest value of DeltaHf°(O2–), obtained for MgO, presumably the most ionic of the crystals treated, a value of 202.3 kcal/mole is obtained. These values are believed to be more accurate than earlier values given by Morris and by Huggins and Sakamoto who obtained 210 ± 6 and 221 ± 15 kcal/mole. The anomalously low value calculated for DeltaHf°(O2–) for ZnO is believed to result from a substantial covalent contribution in the Zn[Single Bond]O bond in this oxide.


Physics of the Earth and Planetary Interiors | 1972

Crystal field effects in mantle minerals

Edward S. Gaffney

The behavior of Fe2+ in the lower mantle will depend on the effects of crystal fields. A point charge model, scaled to fit observed spectra at low pressures is developed to predict these effects. Two of the three parameters needed to predict spin-pairing transitions can only be determined from spin-forbidden electronic transitions. The spectra of garnet, gillespite and peridot are examined and found to have such absorption features. Assignment of these spectra leads to values of the Racah parameters, B and C, as well as the crystal field parameter Dq. A new experimental technique, which allows the measurement of optical absorption spectra of solids in the visible region during shock loading, is described. Results are discussed for periclase and ruby. The ruby data indicate that the point charge model is good to at least 15 percent (volume) compression. The effects of low-spin Fe2+ in the earths lower mantle are investigated in considerable detail. The existence of low-spin Fe2+ permits the formation of a separate phase since Mg2+ and low-spin Fe2+ may not form solid solutions. The bulk elastic behavior of such phases is predicted from volume-bulk modulus systematics and compared with available shock wave data. It is likely that the high pressure phases of several ferrous iron compounds involve low-spin Fe2+ Iron will be spin-paired in the mantle below 1200 km and likely at higher levels as well. The observed density and bulk modulus in the lower mantle are inconsistent with any combination of phases in a pyrolite bulk composition but can be fit quite well by a model with all Fe2+ spin-paired below 630 km and nearly olivine composition at that depth, with MgO decreasing to almost a pyroxene composition at the core. An origin of the upper mantle from the lower mantle by chemical fractionation is proposed. The spin-pairing of Fe2+ provides an excellent mechanism for both iron and silicon enrichment in the lower mantle by partial melting yielding a pyrolite upper mantle, and hence, a chemically inhomogeneous mantle. This removes the motivation for reducing FeO and SiO2 in the mantle to supply Fe and Si for the core.


Physics of the Earth and Planetary Interiors | 1970

Stability of mantle minerals from lattice calculations and shock wave data

Edward S. Gaffney; Thomas J. Ahrens

Abstract Shock wave and static high pressure data for mantle minerals have indicated that at high pressures a series of denser polymorphs form whose crystal structures can at present only be inferred from calculated densities and crystal chemical arguments. In order to determine the admissibility of some of these proposed structures theoretical Madelung lattice energies are calculated for several oxides (FeO, Al 2 O 3 , Cr 2 O 3 , Fe 2 O 3 , SiO 2 , TiO 2 ) spinels (Al 2 MgO 4 , Mg 2 SiO 4 , Fe 2 SiO 4 , Ni 2 SiO 4 , FeCr 2 O 4 , Fe 2 TiO 4 , Fe 3 O 4 ) and perovskites (CaTiO 3 , SrTiO 3 , MgSiO 3 , Fe 2 3+ O 3 , Fe 2+ Fe 4+ O 3 ). Comparison of calculated enthalpies of formation with measured values yield approximate values for the effects of covalency on enthalpies of formation for AlO 6 , TiO 6 , SiO 4 , SiO 6 , Fe 3+ O 6 , Cr 3+ O 6 , Fe 3+ O 4 and Fe 2+ O 4 . This effect is seen to be very similar for the same ion pair in the same coordination but in different compounds. The calculations indicate that enstatite (MgSiO 3 ) can not enter a perovskite with a density greater than about 3.9 g/cm 3 and that the high pressure phase of Fe 2 O 3 can be a perovskite only if the Fe 3+ disproportionates into Fe 2+ and Fe 4+ and the 3d electrons in the latter are spin paired.


Earth and Planetary Science Letters | 2007

Localization of volcanic activity: 2. Effects of pre-existing structure

Edward S. Gaffney; Branko Damjanac; Greg A. Valentine


Journal of Geophysical Research | 1971

Dynamic Compression of Enstatite

Thomas J. Ahrens; Edward S. Gaffney


Journal of Geophysical Research | 1973

Effect of low‐spin Fe2+ on the composition of the lower mantle

Edward S. Gaffney; Don L. Anderson


Geophysical Research Letters | 1980

Identification of Ice VI on the Hugoniot of Ice Ih

Edward S. Gaffney; Thomas J. Ahrens


Journal of Geophysical Research | 1973

Effect of Low-Spin Fe^(2+) on the Composition of the Lower Mantle

Edward S. Gaffney; Don L. Anderson


Journal of Geophysical Research | 1982

Noise and target strength degradation accompanying shallow‐buried explosions

Edward S. Gaffney; H. Jay Melosh

Collaboration


Dive into the Edward S. Gaffney's collaboration.

Top Co-Authors

Avatar

Thomas J. Ahrens

California Institute of Technology

View shared research outputs
Top Co-Authors

Avatar

Don L. Anderson

California Institute of Technology

View shared research outputs
Top Co-Authors

Avatar
Top Co-Authors

Avatar
Researchain Logo
Decentralizing Knowledge