A low altitude detonation or a groundburst will cause a crater to form.
Nuclear detonations that take place near the ground (but not underground) will create a mushroom cloud (this is caused by a Raleigh-Taylor instability).
I have noted that a lower level detonation close to the ground will suck up material into the fireball and create a more pronounced stem.
Many nuclear detonations will create a mushroom cloud (especially near the ground due to material from the ground being sucked up into the vacuum created by the explosion, thus forming a large part of the "stem" of the cloud) and if they are near the ground, will create at least a small crater, but it sounds like you are talking about a groundburst detonation (as opposed to an airburst). These types of explosions carry more radioactive debris from the ground into the air and generate a lot of fallout due to the irradiated debris from the explosion.
surface burstshallow subsurface burstvery low altitude airburstan optimal depth shallow subsurface burst will produce the biggest crater.even conventional explosives produce mushroom clouds, just proportionally smaller with the smaller yield.
The size of the crater created from a nuclear explosion can vary depending on the size of the bomb and the type of terrain it impacts. In general, a nuclear explosion can create a crater several hundred meters wide and tens of meters deep, with larger bombs resulting in larger craters.
It is called a volcano, the hole is for the lava to come out.
A crater is formed when a meteoroid, asteroid, or comet collides with the Earth's surface at a high velocity. The impact creates a depression in the ground, often surrounded by an elevated rim, due to the explosive force generated upon impact.
A nuclear detination
Surface burst
A shallow subsurface burst.
Surface Burst
surface burst
Surface burst
Any type of nuclear explosion will have this effect.
Surface burts
Surface
Surface burst
High yield shallow subsurface.
Surface burst, but any nuclear weapon can be capable of doing that.