In some cases TNT-Minecarts create a massive crater.
to reproduce:
Build a track with 3 powered and normal rails like in the attachment.
The Minecarts have to be 1 Block apart.
Place at least 14 normal rails in a row.
No Activator Rail needed.
better change gamerule to doTileDrops false (or you get laggs!)
Hit the Button and BOOOOOM. Doomsday
edit:
if you extend the normal rails up to 30 or more: crash
Duplicate of MC-6804. Please check before posting in the future.