What can be a synonym for the word frontier when referring to maps

What is associated with mid-ocean ridges?

Heyi am new to are you all americans? ( just want to know , i don't mean any offence ) ?

Venezuela’s economy relies most heavily on which of the followingvenezuela’s economy relies most heavily on which of the following? a. oil reserves in places such as the eastern llanos b. cattle ranching in the grasslands c. fertile farmland in the andean highlands d. coffee plantations in mountainous areas