Does sea level influence mid-ocean ridge magmatism on Milankovitch timescales?

Magma production at mid-ocean ridges is driven by seafloor spreading and decompression melting of the upper mantle. In the special case of Iceland, mantle melting may have been amplified by ice sheet retreat during the last deglaciation, yielding anomalously high rates of subaerial volcanism. For the remainder of the global mid-ocean ridge system, the ocean may play an analogous role, with lowering of sea level during glacial maxima producing greater magma flux to ridge crests. Here we show that the mantle decompression rate associated with changes in sea level is a substantial fraction of that from plate spreading. Modeled peaks in magma flux occur after sea level drops rapidly, including the Marine Isotope Stage (MIS) 5/4 and 3/2 transitions. The minimum in simulated flux occurs during the mid-Holocene, due to the rapid sea level rise at the MIS 2/1 boundary. The model results are highly sensitive to melt migration rate; rates of ~1 m/yr produce small signals, while those >5 m/yr yield substantial anomalies. In the latter case, sea level-driven magma flux varies by 15–100% relative to the long-term average, with the largest effect occurring at slow-spreading ridges. We suggest that sedimentary time series of hydrothermal particle flux, oceanic Os isotopic ratio, and oceanic radiocarbon may serve as proxies for magma-flux variations at mid-ocean ridges. Although well-dated records are rare, preliminary data from the Pacific and Atlantic suggest hydrothermal metal flux was elevated during MIS 2 and 4, broadly consistent with our modeling results

Associations between MMPI-2-RF (Restructured Form) and Inwald Personality Inventory (IPI) Scale Scores in a Law Enforcement Preemployment Screening Sample

The MMPI-2 is widely used in assessments of police officer candidates. The MMPI-2-RF, composed of 338 of the 567 MMPI-2 items, is designed to measure the core clinical constructs assessed by the MMPI-2, but in a more psychometrically sound and efficient manner (Ben-Porath and Tellegen 2008/2011). Law enforcement comparison group data are embedded in the scoring software for the inventory, and reported in the User’s Guide for the MMPI-2-RF Police Candidate Interpretive Report (PCIR; Corey and Ben-Porath 2014). In the present concurrent validity study, conceptually based hypotheses regarding associations between MMPI-2-RF scales and scores on the Inwald Personality Inventory (IPI, Inwald et al. 1982; Hilson Research 2006), a test specifically designed to screen law enforcement officers, were tested with a sample of 277 male, full-time police officer candidates from four separate police departments of varying sizes examined after a conditional offer of employment was tendered. The majority of participants were Caucasian (69%), followed by African-American (27%), or Other/Mixed ethnicity (4%). Our hypotheses were largely borne out, lending support to the construct validity of the MMPI-2-RF and the ability of scores on the inventory to assess variables relevant to police candidate evaluations

Anomalous uplift and subsidence of the Ontong Java Plateau inferred from CO2 contents of submarine basaltic glasses

The Ontong Java Plateau in the western Pacific is anomalous compared to other oceanic large igneous provinces in that it appears to have never formed a large subaerial plateau. Paleoeruption depths (at 122 Ma) estimated from dissolved H2O and CO2 in submarine basaltic glass pillow rims vary from 1100 m below sea level (mbsl) on the central part of the plateau to 2200–3000 mbsl on the northeastern edge. Our results suggest maximum initial uplift for the plateau of 2500–3600 m above the surrounding seafloor and 1500 ± 400 m of postemplacement subsidence since 122 Ma. Our estimates of uplift and subsidence for the plateau are significantly less than predictions from thermal models of oceanic lithosphere, and thus our results are inconsistent with formation of the plateau by a high-temperature mantle plume. Two controversial possibilities to explain the anomalous uplift and subsidence are that the plateau (1) formed as a result of a giant bolide impact, or (2) formed from a mantle plume but has a lower crust of dense garnet granulite and/or eclogite; neither of these possibilities is fully consistent with all available geological, geophysical, and geochemical data. The origin of the largest magmatic event on Earth in the past 200 m.y. thus remains an enigma.<br/