The age of the oceanic crust is determined from radiometrically dated magnetic reversals correlated to the unique patterns of seafloor magnetic anomalies. The age of the crust is further calbrated from the age of the first sediments to accumulate on the volcanic substrate. These early sediments have been recovered and investigated during four decades ocean-floor drilling at hundreds of locations throughout the world's ocean.
The ocean crust is everywhere younger than 200 million years (for example, less than 5% of the age of the earth). The crust is youngest (still being created by volcanic eruptions) along the axis of the mid-ocean ridges and increases in age down the flanks of the mid-ocean ridges and out onto the deeper basin floors. In the Atlantic and Indian oceans the oldest crust is located at the continental margin. In the Pacific Ocean the oldest crust occurs in the far western region. The crust of the greatest age is in the eastern Mediterranean Sea, but here the volcanic bedrock lies too deep beneath the seafloor to be reached and confirmed by current technologies of drilling.
The color image representing crustal ages was created from a digital age grid of the ocean floor with a grid node interval of 0.1 degrees using a self-consistent set of global isochrons and associated plate reconstruction poles by the scientists cited below. The age at each grid node was determined by linear interpolation between adjacent isochrons (lines of equal age) in the direction of seafloor spreading. The ages for ocean crust between the oldest identified magnetic anomalies and continental crust at the edge of the oceans were interpolated by estimating the ages of the passive continental margin from geological data and published plate tectonic models. The quality of the grid is subject to variations depending on data coverage.
The age uncertainties for grid cells coinciding with marine magnetic anomaly identifications, observed or rotated to their conjugate ridge flanks, are based on the difference between gridded age and observed age. The uncertainties are also a function of the distance of a given grid cell to the nearest age observation, and the proximity to fracture zones or other age discontinuities.
Source
These data are available from
NOAA NGDC
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