Geological Time

Geoff Downer

An Introduction to Geological Time

An illustrated review of how geologists date rocks and how the story of the Earth has been divided into a geological time scale.

Event details


10.30am – 4.30pm
A static map of An Introduction to Geological Time

About the event

On this course we will cover the following:

Session 1: Calculating the age of the Earth.

We start with the Rock Cycle which explains the relationship between the three main types of rock and how rocks can change in a recurring sequence.

We then move on to the concept of Deep Time and the Age of the Earth. We shall consider how various philosophers, scientists and eccentrics from the ancient Greeks to the present day have contributed to our understanding of the age of the Earth. We shall finally look at how the age of the Earth is calculated today.

Session 2: The difference between Relative Dating and Absolute Dating.

We shall review a number of fundamental principles that help put geological events into an order. An understanding of these principles helps to relatively date rocks and the various events that can affect the rocks.

We shall then look at how the study of radioactivity has provided the basis for absolute dating. 

Session 3: Stratigraphy and Fossils

Stratigraphy is the branch of geology concerned with the description of rock layers and their interpretation in terms of a general time scale. We shall look at some of the ways in which early geologists described the rocks they saw in the field including the production of the first geological map of the British Isles by William Smith.

Fossils play an important role in dating certain sedimentary rocks and we shall look at some of the ways that geologists have used fossil evidence to help date rocks.

Finally we will look at how the Earth’s magnetic field and certain chemical markers in the past may contribute to geological dating.

Session 4: The Geological Time Scale

The geological time scale relates rock sequences to time and uses terms such as Jurassic and Cretaceous to categorise rock units and past events. We shall look at how the early geologists developed a time scale, how it evolved and how it is defined today.

We shall return once again to the age of the earth and the oldest rocks and bring the story up to the present time with the geological age we currently live in.

There will be a couple of short exercises during the day to test knowledge and develop basic geological skills.

By the end of the course you should have a basic understanding of the following:

  • The difference between relative dating and absolute dating.
  • An appreciation of the contribution made by early British geologists to the development of the geological time scale.
  • How the age of the earth is calculated.

This course is suitable for beginners and Improvers

Led by Geoff Downer, Geologist


Phone number

01622 662012


Normal fee: £35 per person per day.
Concessionary fee: Kent Wildlife Trust volunteers, senior citizens, unemployed and students £5 off.

Know before you go


Guide dogs only


his study day is classroom based.

What to bring

Notebook and pen/pencil
Packed lunch and drinks.


Picnic area
Accessible toilet
Baby changing facilities

Contact us

Jill Evington
Contact number: 01622 662012