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On Google Earth, there are these radiating undersea lines all around Hawaii:

enter image description here

Here with a bit more contrast:

enter image description here

Unlike the other lines, they are pointed away (or toward) a single place.

What are these, how are they called and how did they form?

Weiss
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2080
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2 Answers2

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Short answer: The lines radiating from the island are artifacts from a mapping process that superimposes high-resolution sonar data from standard ship tracks on top of r low- or average sonar data for the region.

Long answer: All the seafloor geography in these maps comes from sonar, ship soundings, or other remote sensing methods and that data is affected by how it is gathered. (Satellites and airborne cameras, radar and lidar can't see through the ocean deeper than a few meters at best, so seafloor imagery is not photographic data.)

Some of the visual elements that appear to be seafloor geography -- notably straight lines radiating away from single points and gridlike formations -- are actually artifacts from the way ships travel. That is, most of the mapping data comes from research vessels using high-resolution sonar while cruising from one location to another, making data collected along those tracks appear much different from the low-resolution details of the general map. As a result, you will often see lines of high-resolution data radiating from ports and islands and grid-like formations where ships have run transects.

Here's a map from the School of Ocean and Earth Science and Technology and the Hawaii Mapping Research Group synthesizing the available data into a more accurate high-resolution representation of the seafloor. Multibeam synthesis map of the Hawaii Islands

Here's one story about how improved data and methodology removed visual artifacts that made people think there was an underground structure in the Atlantic.

The remaining east-west lines are fracture zones that are side-effects of seafloor spreading.

Here's a wider geodetic map of the region from one of the sources used by Google maps where you can see the fracture zones more clearly: Map of seafloor around Hawaii

jeffronicus
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    Are you saying Google maps isn't satellite imagery? – Opifex Jul 13 '22 at 23:25
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    @Opifex indeed... it clearly wasn't visible images (a flight will show the ocean just looks like water from above)... but this Google post discusses a bit more about the bathymetry, as well as this EarthSky one – JeopardyTempest Jul 14 '22 at 01:37
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    @Opifex For the ocean floor it isn’t. You can kind of get some of the seafloor in the shallows, but beyond a certain depth it’s essentially impossible to get useful visual data of anything below the ocean surface from orbit. – Austin Hemmelgarn Jul 14 '22 at 01:38
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    Tbh a lot of Google maps imagery isn’t satellite-based; at least, when you zoom in further. Then the details may be from aircraft instead – fyrepenguin Jul 14 '22 at 05:50
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    @Opifex The North Pole ice isn't shown for example – 2080 Jul 14 '22 at 15:03
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    @Opifex Google Maps is based on satellite imagery provided by TerraMetrics, but includes aerial sources and "synthetic ocean imagery" from other sources, notably Scripps Institution of Oceanography, which integrates bathymetric and gravity data. – jeffronicus Jul 14 '22 at 15:58
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    I think this answer would be improved by making it clearer that the answer to the question is that the lines are artifacts. Maybe a bold sentence at the start, before moving on to describe the geological features (which the OP didn't ask about). – Matt Hall Aug 18 '22 at 17:33
  • @kwinkunks Good idea; edits made. – jeffronicus Aug 18 '22 at 20:27
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Hawai was created by a coat of plume. This means that hot material rises and penetrates the oceanic currents! These are fracture marks from this process.

Secondly, the plate is torn apart by subduction under the N Amrican continent. This contributes to the formation of these fractures

See this figure: enter image description here

Source and also interesting to read: https://www.pnas.org/doi/10.1073/pnas.1300192110

As outher Answers sugesst: it is also a side effect formed by seafloor spreading

Weiss
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  • The OP stated that they were asking about the radiating lines, which are artifacts, not the geologic features. That's my understanding anyway. – Matt Hall Aug 18 '22 at 17:35