Welsh Borderland - Geology: Difference between revisions
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==Geology at depth== | ==Geology at depth== | ||
[[Image:P902281.jpg|thumb|400px| Schematic cross-section of the geology of the Welsh Borderland. The alignment of the section and key are shown in Figure P902280. P902281]] | [[Image:P902281.jpg|thumb|400px| Schematic cross-section of the geology of the Welsh Borderland. The alignment of the section and key are shown in '''Figure P902280'''. P902281]] | ||
Beneath the superficial deposits, or with just a cover of soil where such deposits are absent, are older rocks which geologists broadly split into two distinct types: | Beneath the superficial deposits, or with just a cover of soil where such deposits are absent, are older rocks which geologists broadly split into two distinct types: | ||
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* The basement geology, which underlies the bedrock, is over 415 years old and mainly comprises harder, denser rocks which have been strongly compacted and folded. They include both rocks originally deposited as sediments and others that are products of volcanic activity or formed from the solidification of molten rock below ancient volcanoes. | * The basement geology, which underlies the bedrock, is over 415 years old and mainly comprises harder, denser rocks which have been strongly compacted and folded. They include both rocks originally deposited as sediments and others that are products of volcanic activity or formed from the solidification of molten rock below ancient volcanoes. | ||
The sedimentary bedrock layers composed mainly of sandstones and mudstones are developed at the surface in the north of the region around Shrewsbury and also around Worcester. Elsewhere the basement rocks are exposed at the surface. Figure P902281 provides a vertical section through the geology, referred to as a geological cross-section. | The sedimentary bedrock layers composed mainly of sandstones and mudstones are developed at the surface in the north of the region around Shrewsbury and also around Worcester. Elsewhere the basement rocks are exposed at the surface. '''Figure P902281''' provides a vertical section through the geology, referred to as a geological cross-section. | ||
[[Category:11. Welsh Borderland | 01]] | [[Category:11. Welsh Borderland | 01]] | ||
Revision as of 15:41, 16 October 2014
Recent surface deposits
In the areas around Shrewsbury, Much Wenlock, Church Stretton, Leominster and Hereford there are locally widespread deposits of relatively recent origin formed over the past 2 to 3 million years and spanning the Ice Ages and Interglacial periods. These are known as superficial deposits, the most common of which were laid down by rivers and from glaciers. They typically comprise clays, silts, sands and gravels, which are soft and easily eroded as they have not been deeply buried and consolidated to form strong rocks, and only extend to depths of a few tens of metres.
Geology at depth
Beneath the superficial deposits, or with just a cover of soil where such deposits are absent, are older rocks which geologists broadly split into two distinct types:
- The sedimentary bedrock geology is composed of quite hard rocks which were deposited between about 415 to 200 million years ago as layers of sediments in shallow seas, deserts and vast river systems in times when Britain lay closer to the Equator and the climate and landscape were very different from those of today.
- The basement geology, which underlies the bedrock, is over 415 years old and mainly comprises harder, denser rocks which have been strongly compacted and folded. They include both rocks originally deposited as sediments and others that are products of volcanic activity or formed from the solidification of molten rock below ancient volcanoes.
The sedimentary bedrock layers composed mainly of sandstones and mudstones are developed at the surface in the north of the region around Shrewsbury and also around Worcester. Elsewhere the basement rocks are exposed at the surface. Figure P902281 provides a vertical section through the geology, referred to as a geological cross-section.