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Tag: Mid-ocean ridge

Global Moho depth

Global maps of the Mohorovičić discontinuity, i.e., the Moho depth, across the Earth based on ESA’s satellite observations and the project GEMMA.

Global maps of the Mohorovičić (Moho) discontinuity across the Earth based on observations by ESA’s GOCE gravity satellite and the GEMMA project. While the Moho depth is relatively constant below sea floor, it varies by more than 70 km below continental plates. The Moho is the boundary between the Earth’s crust and its mantle. It is defined by an abrupt density variation of rock causing a change in velocity of seismic waves as they pass through the discontinuity. The Scientific colour map ‘tokyo‘ is used to represent the Moho depth data accurately and to all readers.

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Lithosphere thickness map

Global maps displaying lateral variations in lithosphere thickness across the surface of the Earth.

Global maps displaying lateral variations in lithosphere thickness across the surface of the Earth. Oceanic lithosphere is assigned a thickness proportional to the square root of its age (ages are taken from Müller et al., 1997). For continental areas, characteristic thickness is determined following the method of Gung et al. (2003), who employ the maximum depth for which the seismic velocity anomaly (as determined using the seismic tomography model S20RTSb of Ritsema et al., 2004) is consistently greater than +2%. Moreover, a 100-km thickness is imposed as the minimum continental and maximum oceanic characteristic thickness. It should be kept in mind that material properties such as viscosity vary continuously throughout the depth of the lithosphere, so the definition of thickness may vary. The presented model does not assume any particular definition, but instead characterises lateral variations in layer thickness (see Conrad and Lithogow-Bertelloni, 2006). The Scientific colour map ‘acton‘ is used to represent data accurately and to all readers.

  • Creator: Fabio Crameri
  • This version: 25.10.2021
  • License: Attribution-ShareAlike 4.0 International (CC BY-SA 4.0)
  • Specific citation: This graphic by Fabio Crameri based on data by Conrad & Lithgow-Bertelloni (2006) is available via the open-access s-ink.org repository.
  • Related reference: Conrad, C.P., and C. Lithgow-Bertelloni (2006), Influence of continental roots and asthenosphere on plate-mantle coupling, Geophysical Research Letters, 33, L05312, doi:10.1029/2005GL025621.
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  • Colour-vision deficiency friendly
  • Readable in black&white
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Deep geologic water cycle

A schematic cartoon of the deep water cycle in the Earth’s mantle.

A schematic cartoon of the deep water cycle. Water percolates through the oceanic tectonic plates at the surface, hydrating the oceanic crust and lithospheric mantle below it. When the oceanic plates subduct, part of the water is released at shallow depths (<250 km) into the mantle wedge above the slab. This triggers mantle melting and the formation of volcanic arcs at the surface, in the overriding plate. The rest of the water stays in the slab and is carried deep down into the mantle. Depending on the subduction dynamics, this water can either be released at the mantle transition zone (410-660 km), where large amount of water can be stored in nominally anhydrous minerals, or go even deeper, up to the core-mantle boundary. Part of the water present in the mantle can then be released at the surface again by melt at intraplate volcanoes and mid-ocean ridges as it is transported by plumes and mantle convection.

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