devonian
The Devonian is the fourth period in the Palaeozoic and lasted from 419.2 Mya until 358.9 Mya, in Britain the climate was probably warm to moderate, and frequently arid. This period is characterised by the evolution of plants with leaves, and the diversification of fish with some beginning to walk on land. The Devonian had 3 epochs, the Upper, Middle and the lower or the Early, Mid and Late. Britain was part of the continent containing Scandinavia, Greenland and North-East Canada, most of this was covered by shallow seas, including southern England. At this time, continents were colliding due to the closing of the Iapetus Ocean, so mountain building was occurring forming the Caledonian mountains in northern Britain. These plate tectonics also meant volcanic activity.
England was located around 20°S, so had a hot desert-like climate with limited seasonal rainfall, resulting in flash floods, creating the old red sandstones, conglomerates, red marls, cornstones and grey flaggy beds of lacustrine origin. Most of the geology of the period is found in South-West England, Wales and scattered around Scotland.
England was located around 20°S, so had a hot desert-like climate with limited seasonal rainfall, resulting in flash floods, creating the old red sandstones, conglomerates, red marls, cornstones and grey flaggy beds of lacustrine origin. Most of the geology of the period is found in South-West England, Wales and scattered around Scotland.
The Early Devonian was a warm period, with surface water temperatures of an average 30°C. However, during the mid-Devonian, the concentration of CO2 in the atmosphere dropped as the burial of the new forests forming on land drew the carbon from the atmosphere, leaving temperatures dropping by around 5°C.
During the Late Devonian, coals started to form for the first time in the tropical climate around the equator and glaciers started to cover the south pole. By the end of the Devonian, there was large scale glaciation as CO2 was continuing to be buried by marine life, reducing the greenhouse effect and cooling the planet. This event may be one of the reasons for the mass extinction that ended the Devonian and started the Carboniferous.