# How big of a wave would this falling cliff create?

I'm running a D&D campaign and, well, the players had blown up a cave filled with explosives under a 40-metr cliff. I told them the cliff cracked and fell into the ocean. 40 meters tall, 30 meters into the land, around 60 meters along the coastline from start to finish of a crack. How would it affect the marina in a city nearby? How tall would a wave be? The cliff, I'm assuming would just slide into the water quite fast.

• Argh. I cannot find the citation!!! I once read about a particular cliff (somewhere in the Caribbean) that has a near perfect parabola shape that may cleave off the side of its island, entering the water on a knife edge and widening. Computer models estimated a single wave a couple hundred feet tall resulting, heading toward a Mexico/USA. But I cannot find citation. Maybe your Google karma is better than mine. I do recall that shape mattered as much as mass in the wave created.
– SRM
Feb 8 '20 at 14:15
• Found it! Didn’t start in the Carribean, but it ends there... starts at Isle of Man: theguardian.com/uk/2004/aug/10/science.spain someone else can turn this into a proper answer.
– SRM
Feb 8 '20 at 14:21
• Looks like big, but not massive. Feb 8 '20 at 15:42
• this depends a lot on the sea floor in the area, how deep is the water it is falling into? where do you want the height measured right next to the impact, half a mile away?
– John
Feb 8 '20 at 15:57
• @SRM the article says it starts in the Canary Isles but the chunk of rock is the size of the Isle of Man. Good find though. Feb 8 '20 at 19:04