Understanding Google Earth Ocean Floor Data

With the recent update to the Google Earth ocean floor data it is worth having a look at some of the patterns we can see and what causes them. In the past, some of the patterns have been mistaken for an alien base or Atlantis. However, most of the stranger patterns are merely an artifact of how the data is collected, processed and combined with other data-sets.

In the area around Hawaii, we can see a lot of streaks and swirls. This is a result of an algorithm used to interpolate the sea floor depth between data points and does not reflect the actual appearance of the sea floor. In the above screen shot there is no depth data for most of the central region of the image where the streaks can be seen.

When zoomed out we can often see tracks (1) of higher resolution data, which are the tracks of ships equipped with sonar that mapped the ocean floor along their route. In many cases they have concentrated on mapping the joints between tectonic plates (2) that are of particular interest to oceanographers and geologists.

The tracks also show us the routes the ships took. In the above image we can see the routes fan out from the southern tip of Tasmania as that is the route that would be taken by any ships coming from the east of Australia. Similar patterns can be seen elsewhere, with a fan shapes around Hawaii, the west coast of the US, Cape Town, South Africa, and a number of other locations. There seems to be a popular destination in southern Chile, but the tracks fade away as they approach the coast, so we weren’t able to identify the exact destination. A lot of the ships also went through the Panama Canal. The tracks are highlighted in a graphic in this article that we looked at on Monday. The ships’ tracks are much less visible near the coasts, most likely because higher resolution data is available for shallower coastal waters.

The global low resolution dataset used for the ocean floor is the Scripps map, which is based on satellite measurements of gravity. Although the map gives us a good idea of the large scale structure of the ocean floor it does not show the details and any given measurement may be quite different from the Scripps map. A single measurement will often stand out as a hill or dimple in the overall map, when in reality it may be an unremarkable point on the ocean floor.

In the above image from a location near Guam, we see an area where there has been a survey done with depth measurements taken at very regular intervals. The pattern is caused by combining those measurements with another lower resolution dataset that has a different average depth, so each measurement appears as a dip or bump.

The same effect as mentioned in the previous image can be seen here, but with fewer data points.

As we have mentioned before Google Earth often shows different ocean floor data depending on how zoomed in you are. This is very noticeable around Hawaii and Guam.