a month after the famous quake that hit the major port in Portugal killing tens of thousands.
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Lisbon 1755 quake generated a Tsunami that wiped out Lisbon and importantly, destroyed the Lisbon Library where all the maps and secrets the Portuguese had discovered during their short domination of the seas. The information contained were the crown jewels, the most top eyes only secrets of navigation and world maps.
According to legend, the Portuguese had mapped the entire world including the Americas and Antarctica.
Actually, according to the this century book titled “1421”, everything has been pretty well mapped by the Chinese starting that year until 1423. Unfortunately when the surviving ships returned to China, their sponsor had died, and the new govt. decided to destroy all records and animal and plant samples. A few were saved and there are traces of evidence including DNA in many areas explored then. After a decade a small Chinese delegation arrived in Italy and met with the Pope. Now it is believed the map info held by Portugal and used by Columbus originated from the Chinese voyage(s).