Actually I'm not sure about this pyramid. It could be like Mucky said a trick of light, or just a pyramid shaped mountain.
There are more mountains in the area with the same kind of slopes and angles.
Looked some more on the Southpole to see if I could find anything interesting, but nothing so far.
Then I remembered from long ago, from the time before Google Maps/Earth, I found a triangle shaped area in the Barentszzee.
It wasn't even on the computer, but in a real book with paper pages, called something like the World Atlas.
I had lost the exact location and could never find it back searching with Google, have sought many times without succes.
But now I found it back
here it is: https://www.google.com/maps/dir/73.7767594,20.8021405/Barentszzee/@73.2577427,22.7096157,104077m/data=!3m1!1e3!4m8!4m7!1m0!1m5!1m1!1s0x4454b138bab4d2d1:0x8826e47cd19038f0!2m2!1d37.1063683!2d74.9883921