Learn Farsi: گفته می‌شود که این تنگه‌ی عمیق کنار گسل تشکیل شده است. - It is said that this deep canyon was formed next to the fault.

Yes, you absolutely can. گفته می‌شود is the formal passive construction meaning "it is said." While می‌گویند (they say) is an active, impersonal 3rd-person plural that works perfectly in everyday speech, گفته می‌شود is much more common in news, documentaries, or scientific writing. Given the geological vocabulary here, the formal passive is a great fit.

The English translation says "was formed", but isn't تشکیل شده است the present perfect tense ("has been formed")?

Yes, literally تشکیل شده است means "has been formed." In Farsi, the present perfect is often used for historical, geological, or factual events whose results are still visible and relevant today. English naturally shifts to the simple past ("was formed") for ancient events, but Farsi prefers to highlight the ongoing physical state of the canyon.

Our current lesson covers "dar asar-e" (as a result of). How would the sentence change if we wanted to say the canyon was formed as a result of the fault instead of next to it?

You would simply replace the spatial preposition کنار (next to) with the consequence preposition در اثر (as a result of). The second half of the sentence would become: ...در اثر گسل تشکیل شده است (...was formed as a result of the fault).

How do you change the verb تشکیل شده است to its active form, to say something like "The fault formed the canyon"?

The passive compound verb used here is تشکیل شدن (to be formed). To make it active, you change شدن (to become) to دادن (to give), creating (to form). To say "The fault formed the canyon," you would say .