What ice phenomenon are we seeing in this video?
This phenomenon goes by a number of names: ice heave, ice shove, ice creep, ice tsunami, and I'm sure there are others. It is a consequence of the spring ice breakup coupled with strong sustaining winds on large northern lakes.

The warming spring weather melts the ice close to shore first, making the ice on the lake free-floating. The ice in the middle of the lake can still be close to a meter thick. Winds jostle the ice around, breaking it into chunks. With strong sustaining winds, the ice moves toward the downwind shore. With even stronger sustaining winds, the shoreline is not enough to stop the ice from moving onshore. The ice from further out (and this ice can be very thick) pushes the ice ashore, sometimes bulldozing trees and buildings.

Here's a playlist of 19 youtube videos that portray this phenomenon: https://www.youtube.com/watch?v=0EyfEDKWscg&amp;list=PLPHgakWET6JeATJ1duoGkYItCvfPl26FU . At 32 seconds into the fifth video in the playlist you can see how thick some of the slabs of ice are.