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

2) The highest-grossing concert tour of all time is U2's "360° Tour," which earned over $735 million in ticket sales.

3) The discovery of the Americas by Christopher Columbus in 1492 opened up new trade routes and had a profound impact on world history.

4) The world's largest volcano, Mauna Loa in Hawaii, is also one of the most active. It stands over 13,000 feet (4,000 meters) above sea level.