Often during large landslides, rocks are melted due to the friction between the ground and the bottom layer of the landslide. This is a well studied geological phenomenon and you can find those frictionites (rocks once melted by friction) everywhere on the globe.
But does it have to be a landslide? Maybe a larger earthquake should be enough to warm up some rocks to the melting point? Of course, it happens every day.
Therefore a large collapsing iceberg should also boil some water if all the circumstances are right. I think I saw some fog during those spectacular Youtube clips of Perito Moreno or some other glacier.
It’s kind of sad watching all that mechanical energy converting into useless heat. But then again, it can be very spectacular. There are many glaciers to play with in this world. To watch how a million tons of ice fall into the ocean. If you have triggered the collapse, it’s even better. And so many mountains are also just waiting to be demolished spectacularly.