Secrets of the Ocean Depths – Part 2 of 2
Gösta Lindwall and Mikael Kindborg, July 30, 2020
What are the mysterious structures that can be seen on the ocean floor using Google Earth? In this post we look into visual anomalies of underwater maps, and how to tell the difference between flaws in the mapping technology and true mysteries.
This is the second of two posts about sonar scanning and seafloor maps. Read the first post here.
Multibeam Sonar and Visual Artefacts
The infographic shows a ship equipped with multibeam sonar mapping the seafloor. It swipes the ocean floor in a grid-like pattern of overlapping stripes. Sometimes the process results in visual anomalies that can look like human-made structures.
Multibeam sonar works by sending out multiple sonar beams at different angles to measure the distance to the bottom. The depth data is used to produce a visual map.
Only the middle beam that is going straight down at 90 degrees will get the true measurement of the ocean depth. The other beams in the spread will take longer time to travel though the water, producing distorted depth readings, which is compensated for by computer software.
However, visual artefacts and other errors can occur as a result of the mapping process, which is illustrated in the attached infographic.
Anomalies Created When Combining Scans
When stitching together the bands produced as the ship travels the surface, small differences in measurements of overlapping areas can create visual anomalies.
Artefacts can also occur when combining multiple sonar scans from different ships. Differences in map resolution and measurements can create lines and shadows along the edges of the stripes, giving the impression of roads, buildings, terraces and similar constructions.
Water conditions and bottom type also affect the sonar readings. It is common that sonar scanning expeditions have to recalibrate their equipment to maintain accuracy when sea conditions change.
In online mapping tools, such as Google Earth, a large number of sonar scans from different sources are combined with satellite data to form a seamless view of the ocean floor.
Source images may have different quality and resolution, and there may be differences related to the scanning equipment used.
When images with different characteristics are combined, various visual effects can occur, like straight lines, ripple effects or raster patterns looking like dots on the seafloor. There can be perspective errors, patterns, shadows and other distortions.
Anomalies can also appear as a side effect of the software algorithms used when merging data sources into a kind of puzzle, where overlapping images are fitted together like in a collage.
One typical effect of this process is that some areas of the seafloor appear in higher resolution than others. This can look like a non-naturally occurring pattern, like a big underwater "road" or "airfield".
An related kind of anomaly is the characteristic grid-like patterns and formations that can be observed at various locations around the world. These patterns are a result of the path travelled by the sonar ships. Such patterns can appear in rectangular grids with straight angles, and may look like ancient sunken cities.
Examples of bottom anomalies are easily found when exploring coastal areas around the world on Google Earth.
Many different types of underwater structures can be seen on sonar images. Some of them do not look natural, but appear artificial.
The question is, which structures can be attributed to visual artefacts of the scanning process and the combination of different source images, and which remain a true mystery?
Can seemingly complex structures can appear just as a result of overlapping patterns or shadow effects? Even after researching and learning about possible visual effects and artefacts resulting from the mapping process, it's hard for an investigative mind to not spot what looks like artificial structures on the seabed.
In the attached images from Google Earth, we give one example of what we believe is a scanning anomaly, and one example of what could be a sunken town from the ancient past.
An Example of Sonar Scan Patterns
This underwater map is from Google Earth, around 1,000 km west of San Francisco, US. The location is 37°07'22"N 136°41'08"W. Open location on Google Maps.
The bands that can be seen in this image might be taken for big roads or airfields. But most likely, they are an artefact produced by differences in resolution in the source maps used to compose the image.
If you go to this location on Google Earth and zoom in, you will see that the resolution inside bands are much higher, which indicates a composite image.
The bands are also very wide, around 15 km, which is too big for a realistic scenario including roads or airfields. Further, the depth at this location is around 5,000 m, and this is much deeper than traces of a lost civilization is expected to be found.
One may wonder why sonar scan ships would travel in somewhat random patterns, but it is still likely that these bands are a result of a composite map.
It is common to spot something on Google Earth that looks like a human-made structure, but when you measure it, it is very big. We have seen objects that look like pyramids that are around 10 km wide, which is too big to fit into the known size range of pyramids discovered so far.
Something That Looks Like a Sunken Town
This underwater image is from Google Earth, at the seafloor right outside Long Beach, US. The location of this formation is 33°40'07"N 118°13'44"W. Open location on Google Maps.
The structure shown in the enlarged part of the image. It has a shape and structure that resembles what we could expect the ruins of a sunken town to look like. The length of the formation is 1,740 m and the width is 380 m. The water depth is around 25 m.
This might be the remains of an ancient settlement. We can see a layout of blocks resembling ruins of buildings on the seafloor. In the rectangular area in the top right corner of the enlarged image, what looks like foundations of old buildings are visible.
An alternative explanation could be that this particular strip on the seafloor was surveyed by a ship that used higher resolution sonar than in the surrounding area.
The shallow water depth would make it fully doable to conduct a diving expedition, to find out exactly what is hiding here. It would also be possible to scan the area with affordable side scan sonar from a small boat.
The Future of the Unknown Ocean Floor
The public awareness of underwater structures is changing. People are getting access to resources and information. Google Earth and other satellite image sources are showing sea bed maps.
While funded expeditions may not happen on a large scale, private researchers and enthusiasts can make a difference in the near future.
When the price range for equipment drops, people who have a strong desire to know, can embark on a remarkable adventure in sunken city exploration.
This article has also been published on Facebook in the group Forbidden Archaeology and other Mysteries.