gmt-fork/doc/rst/source/datasets/earth-age.rst_

Global Earth Seafloor Crustal Age Grids
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.. figure:: /_images/EarthByte_logo_small.png
   :align: right
   :scale: 20 %

.. figure:: /_images/GMT_agefig.*
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   :align: center

Numerous geodynamic and geophysical studies consider both the seafloor depth and
the seafloor crustal age. `EarthByte <https://www.earthbyte.org/>`_ has pioneered
the creation of crustal age grids since 1997 and we offer their latest version for
remote use in GMT.

Usage
~~~~~

You access a global crustal age grid by specifying the special name

   @earth_age_\ *rr*\ *u*\ [_\ *reg*\ ]

The following codes for *rr*\ *u* and the optional *reg* are supported (dimensions are listed
for pixel-registered grids; gridline-registered grids increment dimensions by one):

.. _tbl-earth_age:

==== ================= === =======  ==================================================
Code Dimensions        Reg Size     Description
==== ================= === =======  ==================================================
01d       360 x    180 g,p  125 KB  1 arc degree global seafloor ages (1 min @ 111 km)
30m       720 x    360 g,p  402 KB  30 arc minute global relief (1 min @ 55 km)
20m      1080 x    540 g,p  827 KB  20 arc minute global relief (1 min @ 37 km)
15m      1440 x    720 g,p  1.4 MB  15 arc minute global relief (1 min @ 28 km)
10m      2160 x   1080 g,p  2.9 MB  10 arc minute global relief (1 min @ 18 km)
06m      3600 x   1800 g,p  7.3 MB  6 arc minute global relief (1 min @ 10 km)
05m      4320 x   2160 g,p   10 MB  5 arc minute global relief (1 min @ 9 km)
04m      5400 x   2700 g,p   15 MB  4 arc minute global relief (1 min @ 7.5 km)
03m      7200 x   3600 g,p   26 MB  3 arc minute global relief (1 min @ 5.6 km)
02m     10800 x   5400 g,p   56 MB  2 arc minute global relief (1 min @ 3.7 km)
01m     21600 x  10800 g,p  188 MB  1 arc minute global relief (1 min original)
==== ================= === =======  ==================================================

All of these data will, when downloaded, be placed in your ~/.gmt/server directory, with
the earth_age files being placed in an ``earth/earth_age`` sub-directory. If you do not
specify a CPT, the default CPT for this data set will be used (*@age_chrons_GTS2012_2020.cpt*)

Technical Information
~~~~~~~~~~~~~~~~~~~~~

We scale and reformat the original data to take up very little space so that downloads
from the servers are as fast as possible.  For the seafloor crustal age grid this means
we chose 0.01 My as the smallest data unit, which is well below the uncertainties in the
model.  Data are scaled and shifted to fit in a short integer grid that is highly compressed
by netCDF lossless compression and chunking.  The data are reported in Myr relative
to the 2012 Geological Time Scale.

Data References
~~~~~~~~~~~~~~~

#. Seton et al. [2020, in review] [https://www.earthbyte.org/category/resources/data-models/seafloor-age/].