The process of making a rail joint weld

Everything you wanted to know about
thermite welding is here

Sparks fly as the existing joint is widened and ground smooth
The disposable crucible is prepared.
It has two individual sides that surround the joint
The two sides are clampled together
The crucible is pre-heated
The thermite is loaded into the hopper
Thermite burns at an extremely high temperature
>2500C (nearly 5000F)

The setup is ready and the hopper that
contains the thermite is positioned over the crucible

The thermite begins to burn, showering sparks everywhere
It looks like a volcano erupting
The thermite melts a 'plug' in the hopper and flows into the crucible
This compressed air-driven apparatus
is used to break the crucible for removal
The weld is then ground down to proper height
The finished product