What continent is located at latitude 90 degree south longitude 0.00 degree east?
Antarctica, the coordinates you have given is actually for the South Pole, which can be found on Antarctica.
Degrees of longitude are uniform in length. 1 degree (Longitude) = 69.69 miles*Cos(Ө)(latitude) however the length of a degree of latitude depends on were you are on the planet. A degree of latitude at the equator is notable longer than, for example, a degree of latitude at the latitude of Toronto, Canada.