1) The Mariana Trench in the western Pacific Ocean is the deepest part of the world's oceans, reaching a depth of approximately 36,070 feet (10,994 meters).

2) The word "oxygen" contains two vowels: O and E.

3) Mountains are formed through various geological processes, including tectonic plate movements, volcanic activity, and erosion.

4) The word "piano" contains three vowels: I, A, and O.