I had no idea that gravity on earth fluctuated that much.
The Indian Ocean has low density matter beneath it that causes it to be 100m lower than if it were average gravity at sea level.
Giant ‘Gravity Hole’ in the Ocean May Be the Ghost of an Ancient Sea:
https://www.scientificamerican.com/article/giant-gravity-hole-in-the-ocean-may-be-the-ghost-of-an-ancient-sea1/
