Physical parameters (1): Different types of surface
activity
Explosive silicic activity
Plinian column: gas jet + fragments
of magma above 10 km high
A few hours
200 - 300 m/s or more (70 to 1000 km/h)
Pyroclastic flow:
dense gravity
currents
50 m/s (180 km/h)
Lava dome: viscous gravity current
10-5 to 10-4 m/s (4 cm/h to 40 cm/h)
St Helens, 18/05/80 2 pm
Unzen, June1991
Mt Pelée