The four bombers caused the ground to be sliced in a square with Avignon trapped inside.

Only a few grams of iron sand were disseminated from the side of the blade.

Because that metal powder reached a tremendous speed higher than 10,000 kph, an orange flash cut into the ground even though it started from a few thousand meters in the air.

[...]

The first blast had created a trench 20 meters across and 10 meters deep.

Directly afterwards, the trench melted into orange and collapsed. The earth itself was being cooked until it was like magma. And just like that, the old city of Avignon was trapped inside a river of lava. The electricity and water lines and even the Rhone River flowing near the city were severed. The outer circumference had already started to flood.

Now everyone inside the old town of Avignon was completely trapped.

Toaru Majutsu no Index vol.14 ch.4 pt.5