The most likely reason for the described changes, including cracked and moved earth materials, flooding, and extreme erosion, is that a tsunami caused all the damage. Tsunamis are known for their ability to rapidly inundate coastal areas, leading to significant flooding and erosion as well as the dislocation of earth materials. While an earthquake can also cause damage, the specific features mentioned are more characteristic of a tsunami event. Therefore, the correct answer is:
A tsunami caused all the damage.