Such a monumental amount of steam as needed for 30,000 extra feet of water would boil off the earth's atmosphere. The sulphuric acid would poison what was left. Many volcanoes are submarine - there would have to be so many more of those than above water. This means the ocean temps would be raised so much that only those species you find around smokers would survive. Personally, I would love to know how all that water got reattached to the ringwoodite in the mantle.