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'''How do we know the age of the rocks?'''<br>
'''Hydrogeology of Wales'''<br>


[[Image:P785797.jpg|frameless| right|200px| ]]
[[Image:P841814.jpg|frameless| right|200px| ]]


Some originated as layers of sediment on the sea bed or lake floors (so they are called sedimentary rocks) and may contain the fossilised remains of animals or plants. These fossils can give a relative indication of age, with different fossil assemblages appearing in vertical succession (oldest at the bottom, youngest at the top) and each one having a lateral correlation with the same assemblage in other areas. Absolute, or numerical, age determinations are obtained by careful measurement of the proportions of minor radioactive components in igneous rocks (that were once molten), or metamorphic rocks (those much changed by great heat and high pressure). These proportions are ‘frozen-in’ when the molten or reheated rock cools and solidifies, and thereafter the radioactive elements decay steadily at a known rate. By integrating both kinds of evidence (Figure P785797) we can build up an accurate timetable of when things happened.  [[Bedrock Geology UK South: Introduction | '''(Read the full article...)''']]
Wales receives wet westerly winds and is consequently well-endowed with water resources. In addition to its surface waters, Wales also has a wide range of aquifers that reflect its diverse geology, and although groundwater cannot compete with the surface water resources in terms of volume, it does offer a valuable alternative or supplementary source, particularly in rural areas. Groundwater has stable physical and chemical properties, which are beneficial to a number of industries including brewing, distilling, fish farming and dairy processing and it provides a source of alkalinity when blended with the often-acidic surface waters derived from upland gathering grounds. Groundwater is not only an important resource but it also maintains low river flows during drier periods with continued discharge of groundwater base flow into surface waters. Groundwater is also a potential hazard — mine dewatering has taxed Welsh mining engineers ever since the Industrial Revolution.  [[Hydrogeology of Wales: Introduction | '''(Read the full article...)''']]

Revision as of 10:29, 13 January 2016

Hydrogeology of Wales

P841814.jpg

Wales receives wet westerly winds and is consequently well-endowed with water resources. In addition to its surface waters, Wales also has a wide range of aquifers that reflect its diverse geology, and although groundwater cannot compete with the surface water resources in terms of volume, it does offer a valuable alternative or supplementary source, particularly in rural areas. Groundwater has stable physical and chemical properties, which are beneficial to a number of industries including brewing, distilling, fish farming and dairy processing and it provides a source of alkalinity when blended with the often-acidic surface waters derived from upland gathering grounds. Groundwater is not only an important resource but it also maintains low river flows during drier periods with continued discharge of groundwater base flow into surface waters. Groundwater is also a potential hazard — mine dewatering has taxed Welsh mining engineers ever since the Industrial Revolution. (Read the full article...)