The following answers apply;
- Changes in magnetic properties of rock
- Decrease in well water levels
- Increases in radon gas in groundwater
- Foreshocks
These other choices may be good indicators of an imminent volcanic eruption;
Movement of magma
Increase in sulfur dioxide and carbon dioxide ground emissions
C and D are units of length or distance.
A is a measured angle.
B is a unit of angular measurement.
Gravitational energy is a form of potential energy because it is dependent on the mass of an object and needs to be calculated for the specific object.
