physical chemistry - Why exactly does molten NaCl explode, when it is poured into water?

Why does molten $\ce{NaCl}$ explode, when it is poured into water?

$\ce{NaCl}$ has a high melting point, $1074\ \mathrm{K}$ ($801~\mathrm{^\circ C}$). $\ce{NaCl}$ has a molar mass of $58.44\ \mathrm{g/mol}$, it has specific heat capacity of $36.79\ \mathrm{J/(K\cdot mol)} = 629.53\ \mathrm{J/(K \cdot kg)}$. therefore the $\ce{NaCl}$ at melting point temperature has $491,033\ \mathrm{kJ/kg}$ more thermal energy than $\ce{NaCl}$ in STP conditions ($1\ \mathrm{atm}, 20~\mathrm{^\circ C}$, temperature difference $= 780\ \mathrm{K}$)

According to one amateur video in youtube, the molten salt explodes when it is poured into water (c. 2:15)

What is the exact cause of the explosion?

The author of the video reasons that the phenomenon is purely physical and it is caused by that water heats up, vaporises and expands as a gas inside the glimp of very hot $\ce{NaCl}$ salt. But is it really everything that happens there?

Other possible processes present in such occasion are (this is just a list what comes into my mind):

• rapid crystallisation of the $\ce{NaCl}$


• chemical reaction between $\ce{Na}$ and water: $$\ce{2 Na (s) + 2 H2O (l) -> 2 NaOH (aq) + H2 (g)}$$ (this causes explosion if $\ce{Na}$ is inserted into $\ce{H2O}$)


• reaction between $\ce{Cl}$ and water: $$\ce{Cl2 + H2O -> HOCl + HCl}$$



• the rapid solubility of hot $\ce{NaCl}$ into water


• thermal decomposition (thermolysis) of $\ce{H2O}$ into either monoatomic or diatomic hydrogen and oxygen, and reactions that follow this.

Also, the author fails to explain why no explosion occurs with sodium tetraborate nor sodium carbonate when each of them, in molten state, was poured into the water.