Geology is all about reconstructing the past. A major factor in this is to identify the environment in which particular rocks are deposited.

There are numerous lines of evidence used to reconstruct the environments in which rocks are formed, both in the field and from laboratory analysis.

The importance of accurate environmental reconstruction is obvious when you consider how much they have changed over time. On Arran for example,parts of what is now land, has in the past been in an ocean, and other parts have been at different times, in a desert. Volcanoes and rivers are also represented, as are rocks which have been altered deep in the Earth's crust.

This section describes some of the major past environments represented on Arran. It explains the types of rocks that are found in the different environments, and the characteristics of the rocks that help you determine where they formed.