One thing scientists are checking for is to see if any areas stand over underground cavities which may give way.

The heat from the blast melts the rock, instantly creating a huge underground cavity.

Certain areas will have old mines and underground cavities which need investigation.

In some underground cavities, water may actually be holding up a thin overhang of earth.

Geologists have warned that the line passes through land prone to collapse because of underground cavities.

The area often suffers from landslides which may also be as a result of this underground cavities.

At the point of explosion, the nuclear fireball carves out an underground cavity.

How quickly an underground cavity near the surface collapses is dependent on various factors.

They probably make use of pre-existing underground cavities as the legs do not show adaptations for digging.

Tunnel warfare is a general name for the war being conducted in tunnels and other underground cavities.