A new 1 km global IIASA-IFPRI cropland percentage map for the baseline year 2005 has been developed which integrates a number of individual cropland maps at global to regional to national scales. The individual map products include existing global land cover maps such as GlobCover 2005 and MODIS v.5, regional maps such as AFRICOVER and national maps from mapping agencies and other organizations. The different products are ranked at the national level using crowdsourced data from Geo-Wiki to create a map that reflects the likelihood of cropland. Calibration with national and subnational crop statistics was then undertaken to distribute the cropland within each country and subnational unit. The new IIASA-IFPRI cropland product has been validated using very high-resolution satellite imagery via Geo-Wiki and has an overall accuracy of 82.4%. It has also been compared with the EarthStat cropland Global Change Biology (2015Biology ( ) 21, 1980Biology ( -1992Biology ( , doi: 10.1111 product and shows a lower root mean square error on an independent data set collected from Geo-Wiki. The first ever global field size map was produced at the same resolution as the IIASA-IFPRI cropland map based on interpolation of field size data collected via a Geo-Wiki crowdsourcing campaign. A validation exercise of the global field size map revealed satisfactory agreement with control data, particularly given the relatively modest size of the field size data set used to create the map. Both are critical inputs to global agricultural monitoring in the frame of GEOGLAM and will serve the global land modelling and integrated assessment community, in particular for improving land use models that require baseline cropland information. These products are freely available for downloading from the http://cropland.geo-wiki.org website.

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A 20-Myr record of creation of oceanic lithosphere is exposed along a segment of the central Mid-Atlantic Ridge on an uplifted sliver of lithosphere. The degree of melting of the mantle that is upwelling below the ridge, estimated from the chemistry of the exposed mantle rocks, as well as crustal thickness inferred from gravity measurements, show oscillations of approximately 3-4 Myr superimposed on a longer-term steady increase with time. The time lag between oscillations of mantle melting and crustal thickness indicates that the mantle is upwelling at an average rate of approximately 25 mm x yr(-1), but this appears to vary through time. Slow-spreading lithosphere seems to form through dynamic pulses of mantle upwelling and melting, leading not only to along-axis segmentation but also to across-axis structural variability. Also, the central Mid-Atlantic Ridge appears to have become steadily hotter over the past 20 Myr, possibly owing to north-south mantle flow.

Land cover is of fundamental importance to many environmental applications and serves as critical baseline information for many large scale models e.g. in developing future scenarios of land use and climate change. Although there is an ongoing movement towards the development of higher resolution global land cover maps, medium resolution land cover products (e.g. GLC2000 and MODIS) are still very useful for modelling and assessment purposes. However, the current land cover products are not accurate enough for many applications so we need to develop approaches that can take existing land covers maps and produce a better overall product in a hybrid approach. This paper uses geographically weighted regression (GWR) and crowdsourced validation data from Geo-Wiki to create two hybrid global land cover maps that use medium resolution land cover products as an input.Two different methods were used: a) the GWR was used to determine the best land cover product at each location; b) the GWR was only used to determine the best land cover at those locations where all three land cover maps disagree, using the agreement of the land cover maps to determine land cover at the other cells. The results show that the hybrid land cover map developed using the first method resulted in a lower overall disagreement than the individual global land cover maps. The hybrid map produced by the second method was also better when compared to the GLC2000 and GlobCover but worse or similar in performance to the MODIS land cover product depending upon the metrics considered. The reason for this may be due to the use of the GLC2000 in the development of GlobCover, which may have resulted in areas where both maps agree with one another but not with MODIS, and where MODIS may in fact better represent land cover in those situations. These results serve to demonstrate that spatial analysis methods can be used to improve medium resolution global land cover information with existing products.

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[1] We obtained areal variations of crustal thickness, magnetic intensity, and degree of melting of the subaxial upwelling mantle at Thetis and Nereus Deeps, the two northernmost axial segments of initial oceanic crustal accretion in the Red Sea, where Arabia is separating from Africa. The initial emplacement of oceanic crust occurred at South Thetis and Central Nereus roughly $2.2 and $2 Ma, respectively, and is taking place today in the northern Thetis and southern Nereus tips. Basaltic glasses major and trace element composition suggests a rift-to-drift transition marked by magmatic activity with typical MORB signature, with no contamination by continental lithosphere, but with slight differences in mantle source composition and/ ©2012. American Geophysical Union. All Rights Reserved.1 of 29 or potential temperature between Thetis and Nereus. Eruption rate, spreading rate, magnetic intensity, crustal thickness and degree of mantle melting were highest at both Thetis and Nereus in the very initial phases of oceanic crust accretion, immediately after continental breakup, probably due to fast mantle upwelling enhanced by an initially strong horizontal thermal gradient. This is consistent with a rift model where the lower continental lithosphere has been replaced by upwelling asthenosphere before continental rupturing, implying depth-dependent extension due to decoupling between the upper and lower lithosphere with mantle-lithosphere-necking breakup before crustal-necking breakup. Independent along-axis centers of upwelling form at the rifting stage just before oceanic crust accretion, with buoyancy-driven convection within a hot, low viscosity asthenosphere. Each initial axial cell taps a different asthenospheric source and serves as nucleus for axial propagation of oceanic accretion, resulting in linear segments of spreading.

Pyroxenite layers embedded within peridotite represent widespread lithological mantle 2 heterogeneities and are potential components in the mantle source of many oceanic basalts. 3 Pyroxenites can be generated by several magmatic and metamorphic processes. However, in 4 most natural samples (especially in ultramafic massifs), their primary characteristics are 5 partially or completely erased by later petrologic evolution (e.g. metamorphism, metasomatism or partial melting). Here we investigate a suite of pyroxenites from the 7 External Liguride Jurassic ophiolites (Northern Apennines, Italy). They are spinel-bearing 8 websterites and clinopyroxenites, partially recrystallized under plagioclase-facies conditions, 9 and occur as cm-scale layers parallel to the tectonite foliation of their host peridotites. 10 Pyroxenites have bulk Mg-numbers from 74 to 88 and display rather constant LREE depletion 11 over the MREE (La N /Sm N = 0.15-0.35), but variable MREE-HREE fractionation, with some 12 of them having markedly positive HREE slopes (Sm N /Yb N =0.30-0.96). The HREE 13 enrichment coupled with high Zr and Sc contents in clinopyroxene porphyroclasts from 14 spinel-bearing domains provides strong evidence that garnet was present in the precursor 15 mineral associations. Mass balance calculations suggest that the pyroxenites originally 16 contained up to about 40 vol% of garnet, indicating they originated by segregation of melts at 17 rather high pressure (P > 1.5 GPa). Parental melts of pyroxenites have reacted to some extent 18 with the host peridotite during mantle infiltration. Lack of olivine in the primary mineral 19 assemblage and orthopyroxene-rich rims along the contact with wall-rock peridotites indicate 20 that pyroxenites have crystallized from silica-rich melts. These, likely, had REE patterns and 21 Sr-Nd isotope compositions similar to enriched MORB. We propose that the pyroxenites 22 originated from melts derived from a hybrid eclogite-bearing peridotite source, and then 23 reacted with the host peridotite to form "secondary pyroxenites". Their existence has been 24 invoked in current models of basalts petrogenesis. During later decompression, they 25 experienced an intermediate recrystallization at spinel-facies conditions, at 1.2-1.5 GPa and 26 minimum temperature of 950-1000°C, and partial re-equilibration at low-pressure 27 plagioclase-facies. The latter is dated by internal Sm-Nd isochrons at 178 (±8) Ma and is 28 associated with Mesozoic exhumation, during extension of the Tethys lithosphere.

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