An interesting aspect of the ‘historical imagery’ feature in Google Earth is that when you turn it on Google Earth displays a different dataset for the ocean floor. Based on the copyright information, it appears the ‘historical imagery’ ocean floor is based on data from NASA, whereas the ocean floor seen in the default view is a combination of data from Data SIO, NOAA, U.S. Navy, NGA and GEBCO.
The NASA supplied data as seen in ‘historical imagery’
The default view with data from a variety of sources
It is interesting how whole underwater mountains are completely missing in the NASA data and some locations look quite different in the two data sets. The NASA data is of lower resolution and presumably obtained by a different method.
Another interesting effect is how satellite imagery that extends into the oceans is mapped onto the sea floor topography. If necessary you can correct this in Google Earth Pro by turning off ‘Terrain’ in the layers.
As we have noted in the past the tracks across the ocean floor are not signs of alien activity, but tracks of higher resolution data obtained from ships.
We have also looked at a map from the Scripps Institution of Oceanography, University of California, San Diego, which is based on gravity measurements from satellites. You can view it in Google Earth with this KML file.
For best results when viewing the ocean floor, turn off the ‘Water Surface’ option in the ‘View’ menu.