Geology

Questions:

  1. What types of rock lie beneath Swansea beach’s blanket of mud and shells.
  2. Do the pebbles at the top of the beach come from the local rocks or are they undocumented migrants?
  3. And, for that matter, where does the mud come from?
  4. And why so many shells?
  5. Is it the mud that attracts the shells? Because there are nowhere near as many on cleaner beaches not so many miles away.

Answers:

  1. I don’t know.
  2. I don’t know.
  3. I don’t know.
  4. I don’t know.
  5. I don’t know.

With a view to improving on the above answers, I shall go away and do some research. But let me get to grips with WordPress first.

The following information comes from Geology of the Swansea District, a British Geological Survey publication:

The Swansea district extends from Gower and Llanelli in the west to Port Talbot and Neath in the east, the city of Swansea occupying much of the central part. Carboniferous rocks underlie (almost) the entire district. This geology determined the pattern of human activity.

Coal was the mainstay of the district’s economy from the 16th century until the 1940s, with Swansea, Llanelli and Port Talbot exporting coal produced locally and from elsewhere in the coalfield. Following the rapid late 20th century decline of the coal industry, there is no mining in the district, except for one small opencast operation.

Mineral smelting becme an important industry in the 18th century, using local coal. Copper, tin, lead and zinc ores were imported from Cornwall and around the world. Today, the tinplate works at Swansea and Llanelli and the steel works at Port Talbot are the only remnants of this industry.

Light industry and the service sector provide most employment today, but equally important is the growing leisure and tourism industry based round the fine beaches of the Gower peninsula.

In short, a decline from honest labour to call centres and hospitality.

What is the ground under our feet in the Swansea area composd of? The geology surveys mention:

  • Mudstone (a fine-grained sedimentary rock whose original constituents were clays or muds).
  • Sandstone (a clastic sedimentary rock composed mainly of sand-sized (0.0625 to 2 mm) mineral particles or rock fragments (clasts) or organic material. Most sandstone is composed of quartz or feldspar (both silicates) because they are the most resistant minerals to weathering processes at the Earth’s surface. Like uncemented sand, sandstone may be any color due to impurities within the minerals, but the most common colors are tan, brown, yellow, red, grey, pink, white, and black).
  • Quartz (a crystalline mineral composed of silicon and oxygen atoms linked in a continuous framework of SiO4 silicon–oxygen tetrahedra, with each oxygen being shared between two tetrahedra, giving an overall chemical formula of SiO2. Quartz is the second most abundant mineral in Earth‘s continental crust, behind feldspar)
  • Carboniferous limestone around 900m thick crops out in east Gower and forms most of the sea cliffs and foreshore between Oxwich Point and Mumbles head. That’s 900 metres of compressed shells, 900 metres of sequestered carbon dioxide.