если можете поделиться ресурсами,
где описаны употребления предлогов
и артиклей с географичекими названиями,
буду очень рада :)

Спасибо.

Не знаю насчет ресурсов онлайн, но Cambridge Advanced Learner's Dictionary по-моему был отдельный раздел про географические названия, если правильно помню.

Referring to geographical names or areas, we tend to use the definite article with:
seas (the Atlantic, the Pacific, the North Sea)
mountain ranges (the Alps, the Andes)
island groups (the British Isles, the West Indies)
areas (the Midlands, the Lake District, the Middle East)
rivers (the Danube, the Blue Nile, the Thames)
deserts (the Gobi, the Sahara)
hotels and pubs (the Red Lion, the Grand Palace)
cinemas and theatres (the Playhouse, the Majestic)
We generally use no articles with:
continents (Africa, South America, South East Asia)
counties and countries (Oklahoma, Bulgaria, Nigeria)
towns and principal buildings (Ely Cathedral, Oxford University)
lakes (Lake Como, Lake Windermere, Derwent Water)
mountains and volcanoes (Everest, Etna, Vesuvius)
Of course, there are always exceptions: The UK, The USA, The UAE, The Netherlands, The Hague. It is just a matter of learning them!

Про артикли: http://www.usingenglish.com/handouts/answers.php?id=219