I am now fascinated by how those people can cut ice at the right angle to not have it fall on them... they are interlocking, and sure, its ice/snow, but with no measurements, by hand, just eying it. That is pretty impressive.
You cut adjustments as you place the blocks, a saw slides right through blocks of snow so it is easier than it looks. I haven't made such a large igloo, but getting the blocks cut right isn't the hard part.
The material might actually help. I'm guessing that as you slide the blocks against each-other, friction melts the surfaces. When the blocks settle, the surfaces re-freeze, gluing them together.
They pack the gaps with snow and the blocks are cut on an angle so they are larger on the outside than the inside. Also, igloos aren't built out of ice. It's compacted snow. Much easier to work with.
