Just a heads up on how to use TNT effectively.
TNT tends to only crash the server when *YOU* trigger it, or if its very closely packed, or if you affect a lot of water/lava at the same time (i.e. blast under a lake). It causes all sorts of issues with the local client communications and can make everything fall over.
I have found an upper limit of client side detonations to be in the region of a few hundred blocks of TNT before things start getting iffy.
A work around for this is to use a "remote trigger".
Remote Blasting 101
Use /setwarp to create a nice viewpoint of your blast area. Then go down to where you want to blast.
What you do is you setup your TNT in a 5x5 grid (something like this)
Where T = TNT and O = other existing blocks like dirt and stone.
You can repeat this pattern as much as you like. For example i have made a version of this where the corners extend as pilars down to bedrock : eg
Then what you do is create a "cup" sat on the top of the tnt. i.e. a few blocks of TNT arranged like this
Where T = TNT and A = air
Then place a few blocks of LAVA into the cup, until theres a little pool (do this quickly) then use /warp to get to the viewpoint setup earlier.
Now you wait, usually about 20 seconds, while the lava ignites the TNT. Then once it does you will see blocks disappear as you get chunk updates from the server. Because all the blasting is done server side your client wont slow down at all and its all good.
I have happily detonated 2500+ block blasts without *ANY* issues using this method.
Note: Using "red dust" as a remote trigger *DOES NOT WORK* like this. "red dust" triggered TNT is considered to be triggered by YOUR client and thus will happen on your machine the same as if you triggered it personally, not the server.
Note2: The massive crater in the above images was "man made" using columns of TNT. I think we have probably set off in the region of 30k TNT there now.
Note3: If the lava pool is touching the skybox (i.e. at the upper build limit) it will not trigger the TNT. You need to have a few air blocks above the TNT/Lava for it to trigger properly.