Britain on the Move 2: The Mesozoic and Cenozoic Eras

The Mesozoic era started 225 million years ago. A massive extinction event brought the permian period to an end and started the Triassic. This didn't actually change Britain very much as our area was still firmly in desert lands - see the blog on Britain in the Palaeozoic for a description of what this was like. The map below shows how the major land areas of the world were arranged at that time. Britain was about 18 degrees north of the equator.

What the Syllabus Says - and the Details

For Britain, the most interesting periods of the Mesozoic were the Jurassic and Cretaceous. During these periods Britain was 30o - 40o north of the equator and covered with  shallow seas similar to those found in the less polluted parts of the Mediterranean today. Inevitably, this 

type of environment caused the development of large areas of limestone during the Jurassic, such as this outcrop on the North Somerset coast.

In the Cretaceous a special type of very pure limestone called chalk was deposited as the water had very little sediment brought into it from land areas.

The Mesozoic was when Africa separated from America to give rise to what we now call the Atlantic Ocean. This happened over an extended period from 200 to 180 million years ago. Such crustal splitting always happens with major extrusive igneous activity (see plate tectonics blog) - we some see evidence for this in the form of Jurassic basalt developments; the best ones happen to be under the North Sea!

During the Cenozoic era the Atlantic has continued to open. In the early Tertiary period this gave rise to the development of thick flood basalts along the west coast of Scotland and Ireland such as these a Drumadoon Point. The thickness of these deposits means that they

cooled slowly enough to produce columnar jointing - best seen at 'The Giant's Causeway' in Ireland.

Also during the Cenozoic era Britain has moved from 50 degrees to 60 degrees North of the equator. This has meant that during the glaciations of the Quaternary Period Britain has been far enough north to be covered with ice, the map below shows how far the ice got in the last glaciation.

The ice scoured the landscape, removing large amounts of material (see sedimentary rocks blog). When the ice melted the material was left behind as glacial till, a mixture of very large, medium and fine material containing a lot of clay - as shown in the picture below.

For a detailed wander through how Britain got to be as it now is click this link  How Britain Formed to get to a really well presented and informative site.