Magnitude and speed of onset - V&E

What does VEI stand for?

Volcanic expolsivity index

When is VEI calculated?

After the eruption

What scale is the VEI?

1 to 8

What is meant by magnitude?

The measurement of scale of size of impact of an earthquake or volcano

What does the bigger magnitude mean?

The more violent

What has to be considered other than magnitude and speed of onset?

Secondary hazards and factors - eg location (urban or rural), level of development, tsunamis, resources, emergency systems

What does the magnitude scale go up to?

1 to 10

What does the Mercalli scale go from?

I to XII

What is the speed of onset?

The time between the start of the event and it’s peak

When would the peak be for a volcano or earthquake?

For a volcano it is when it erupts and for a earthquake it is when it occurs

What is volcano speed of onset like?

It varies - can be a long or short time between start and eruption due to gases, smoke and tremors

What is the earthquake speed of onset like?

Very short onset - no warning so more deaths

What impacts earthquakes speed of onset?

Earthquake proof buildings and tsunamis can take hours

What are examples in volcanic differences in speed of onset?

Montserrat was long and Mt St Helens was short