Hi everyone,

I'm wondering why the sentence below includes "собой":

"Многочисленные действующие вулканы ... гейзеры, горячие источники, лавовые поля и ледники покрывают собой почти всю территорию страны."(Source: Wikipedia)
I get that active volcanoes, geysers etc. cover almost the territory/area of the country as a whole.

Reading about geographical facts of some countries, however, I can remember to have come across sentences like "Леса покрывают ... ".

What's the deal with собой and this particular verb? What difference would it make if I didn't use it in this case?