This melt water has a relatively low density, so it accumulates in the top layer of the ocean.

BBC: Melt may explain Antarctica's sea ice expansion

There are plenty of areas of San Francisco that are relatively low-density, but it is ridiculously hard to develop or redevelop anything.

FORBES: Are Technology Startups Ruining San Francisco?

Oil is found in relatively few places, and its energy density, pumpability and ease of use in internal-combustion engines makes it particularly well suited as a transportation fuel.

ECONOMIST: Unconventional gas