The location for each mushroom-shaped bomb was chosen for the hardness of its surrounding materials.

When the rising pressure and moving water overcame the soil's strength, it suddenly shifted, taking surrounding material - and the wall - with it.

Since the sediment is more permeable than the surrounding materials, it channels fresh water to thin spots in the coral, creating the fresh water springs called wonky holes.

In the regenerator and in the heat exchanger the heat contact between the gas and its surrounding material is good.

Because of the high effective temperatures, hot electrons are very mobile, and likely to leave the semiconductor and travel into other surrounding materials.

The radioactivity of the materials used can also cause radiation corrosion in the surrounding materials.

Explosives with an oxygen deficit will generate soot or gases like carbon monoxide and hydrogen, which may react with surrounding materials such as atmospheric oxygen.

Chemical reaction: An exothermic reaction between chemicals that could release sufficient heat to ignite the surrounding materials.

Magnetic flux always forms a closed loop, as described by Maxwell's equations, but the path of the loop depends on the reluctance of the surrounding materials.

This surrounding material forms a tube enclosing the ray, but does not incorporate the ray path itself.