In this video, Dr Wim Degruyter explains the differences between regular and extreme events.

The film crew caught up in the eruption on Mount Etna described this event as ‘extremely scary’. One volcanologist said it was the most dangerous incident he had experienced in 30 years.

This event was extreme to them because they were so close to a natural hazard and had never experienced something so dangerous in their lifetimes.

This helps us to consider one way we could define an extreme geological event:

An event driven by a natural process that presents a large risk to life [scale] and is very rare [frequency] for a human to experience.

The scale or size of an event, and how frequently it occurs, are certainly key. But, as many geological events happened well before humans were around to witness them, this discounts this definition.

Timescales

One of the key ways we can begin to answer the question:

What is regular activity and what is an extreme event?

Is to understand the timescales over which we look at and compare events. We’ve referred to two timescales already, that we’ve called:

Cosmological

A timescale that begins from the very start of the universe, believed to be 14 billion years ago.

Geological

A timescale that begins from the formation of the Earth, believed to be 4.5 billion years ago.

If we look at the Mount Etna eruption over those timescales and compare it with volcanic eruptions that have occurred on our planet. We will see that this event was neither rare nor large enough to be truly extreme.

So at this stage, the key thing to remember is that we’re going to be comparing events over timescales of millions and billions of years, well before human history.

We’ll start to unpack this by looking at the the first and ultimate extreme event, the origin of the universe.