EMAG2v3: Earth Magnetic Anomaly Grid at 2-arc-minute Resolution, Version 3
EMAG2v3 is compiled from
ship, and airborne magnetic measurements. Magnetic anomalies result from geologic features enhancing or depressing the local magnetic field. These maps increase knowledge of subsurface structure and composition of the Earth's crust. Global magnetic anomaly grids are used for resource exploration, navigation where GPS is unavailable (submarine, directional drilling, etc.), and for studying the evolution of the lithosphere.
The 2017 release of the
EMAG2v3 utilizes updated precompiled grids and a revised process for accurately incorporating the long-wavelength anomalies, as modeled by the satellite-based MF7 lithospheric field model. It is an update from the previous EMAG2v3 released by NCEI in 2016. EMAG2v3 further differs from the previous
EMAG2 (version 2, see link at the bottom of this page), which relied on an ocean age model to interpolate anomalies into non-existent data areas and on the earlier MF6 model. EMAG2v3 relies solely on the data available. As a result, EMAG2v3 better represents the complexity of these anomalies in oceanic regions and accurately reflects areas where no data has been collected. The current version reports anomalies in two ways:
A consistent altitude of 4 km (referred to as Upward Continued)
This version (2009) is a significant update over our first global magnetic anomaly grid, EMAG3. It relies on ocean age models to directionally grid anomaly data into areas where no data exists. The grid is reported at an altitude of 4 km.
This version (2007) is a 3 arc-minute resolution magnetic anomaly map. It was the NGDC (now NCEI) candidate for the World Digital Magnetic Anomaly Map at 5 km altitude.
The global magnetic map illustrates Earth evolution (plate tectonics and crustal interaction with the deep mantle).
Distinct patterns and magnetic signatures are attributed to the formation (seafloor spreading) and destruction (subduction zones) of oceanic crust, and the formation of continental crust by accretion of various terrains to cratonic areas and large scale volcanism (both on continents and oceans).
Magnetization is weaker at the equator and stronger at high latitudes, reflecting the strength of the ambient geomagnetic field, which induces magnetization in rocks
Stripes of alternating magnetization in the oceans are due to sea floor spreading and the alternating polarity of the geomagnetic field
Very old crust (North American Shield, Baltic Shield, Siberian Craton) have strongest magnetization, seen as dark shades of purple and blue