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Changing timescales

All of the types of events we look at this week highlight the fact that we live on a dynamic planet.

It has been said that change is the only constant in Earth’s history.

The largest and most extreme types of earthquakes, volcanic eruptions, floods and tsunamis have all played an important role in the development of the planet.

The deep Earth processes behind some of these events have slowly shaped the planet over geological timescales. The most extreme geological events have, however, led to more rapid and profound changes.

Week 2 timescales

At the beginning of Week 1, we asked what is regular activity and what is an extreme event? We highlighted the importance of considering the timescales over which we look at and compare events.

In Week 1 we considered events over cosmological and geological timescales.

In Week 2 we’ll be considering events over geological timescales and as reminder we defined this as:

Geological timescale

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

Defining events

In terms of definitions we could also attempt to define the difference between regular and extreme events on geological timescales:


A frequent event throughout our planet’s history and of the size or scale that compares with many other similar events.


A rare event over the course of our planet’s history and of a size or scale that has either none or very few comparative events.

As you can see from the definitions, frequency is a key consideration when deciding on whether an event is extreme or not.

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Extreme Geological Events

Cardiff University

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