Observations of a blown mind

Geology


It’s Geological really

The bible teaches that God made the heavens and the earth in 6 days and then had a rest on the 7th day. Many theologians and creationists, and Jehovah’s Witnesses of course, point to the fact that what the bible states as days are in fact longer periods of time. They argue that scriptures such as 2 Pet 3:8 show that a day with God is like a thousand years.

Even so, this does not allow for the reality that surrounds us in the geological record. Living in Britain we have a fantastic geological record on our doorstep which for Evolutionists and Atheist’s alike is one of many ‘proofs’ that the bible is an inaccurate book and that god is a man made ‘creation’.

An element of this geological record is Limestone. As mentioned above around Britain there can be found many fine examples of this record; the White Cliffs of Dover (limestone in its purer form of chalk), the Yorkshire Dales, the coast of Cornwall. Other fine examples found inland containing large limestone deposits from ancient reefs, such as the exposed limestone in Guadalupe Mountains National Park in New Mexico.

What is Limestone?

Limestone is an organic, sedimentary rock made up of calcite (CaCO3) as its main mineral. This means it was formed from the remains of tiny shells and micro-skeletons deposited on the sea bed. Many invertebrate animals (animals with no backbones) take calcite from sea water to construct their shells. When they die the shells fall to the sea bed. Areas where there is little deposition of mud or sand is ideal for the formation of limestone.  Some of these organisms can construct mounds of rock known as reefs, building upon past generations. Below about 3,000 meters, water pressure and temperature conditions cause the dissolution of calcite to increase nonlinearly, so limestone typically does not form in deeper waters (see lysocline). Limestones may also form in both lacustrine and evaporite depositional environments.

The history of limestone formation is told nicely below, in this text passage from a book on the Geography of Michigan“Even in these early warm seas another force was at work building rocks. In some way, the first bacteria and one-celled plants learned to take lime (CaCO3) from the water; they collected in jelly-like masses. Lime collected on these early plants, layer upon layer, and built up into great masses of limestone. Later, when animals came upon the earth they were also one-celled creatures living in the sea, but as they struggled for existence they evolved to more complex creatures, and in time they also took lime from the sea water to make protecting external coverings or shells. When these creatures died their shells fell to the sea floor, accumulated in thick masses, were also broken to lime muds, but all in time became limestone rock – the cemeteries of the animals which lived in the seas, and the museums in which the records of past life (fossils) are preserved.

Gradually, as the Paleozoic seas deepened, almost 2/3 of the North American continent was submerged. As the Ordovician period began in Michigan, the shoreline probably pushed farther northward, as we find traces of early Ordovician limestones in Houghton County. The rock and fossil records show us that this time lasted for 70 million years. At first the seas were deep and clear, a situation which is conducive to the deposition of lime muds, and the eventual formation of limestone. These muds were laid down on the sea floor, which became the graveyards of millions of shelled creatures that lived in the first of the Ordovician seas. Gentle earth movements, or perhaps climatic changes, later caused the late Ordovician seas to be alternately shallow and muddy, or deep and clear, thus the sediments of the late Ordovician became shales and limestones. The Ordovician-aged Trenton limestone supplies building material and crushed stone for road building and fresh water. It is a source of petroleum in the southern part of the Southern Peninsula and potential source of oil within the basin.

Again the seas deepened, genial climates set in, the seas were warm and clear. A new period, the Silurian, set in. Algae and bacteria precipitated lime brought to the sea in solution by clear streams, millions of shelled creatures swam about, corals built long coral reefs, and great thicknesses of lime muds were built up. Over 1600 feet of Michigan limestones are Silurian in age. The thickest and perhaps the hardest of these are the rocks we term Niagaran.”

One type of limestone which is very pure is called chalk [see below], but most other limestones contain variable amounts of mud or sand or other material. They were compressed to form solid rock. Limestone is made up of calcium carbonate and reacts with diluted hydrochloric acid. Limestone is formed in layers – called bedding planes. These bedding planes contain vertical cracks called joints. Joints and bedding planes make the rock permeable.

Chalk

Chalk is a soft, porous rock made up of the skeletal parts of microscopic marine organisms. Ninety million years ago the chalk downland of Northern Europe was ooze accumulating at the bottom of a great sea. Protozoans such as foraminifera lived on the marine debris that showered down from the upper layers of the ocean. Their shells were made of calcite extracted from the rich sea-water. As they died a deep layer gradually built up and eventually, through the weight of overlying sediments, became consolidated into rock. Later earth movements related to the formation of the Alps raised these former sea-floor deposits above sea level.

Chalk is composed mostly of calcium carbonate with minor amounts of silt and clay. It is normally formed underwater, commonly on the sea bed, then consolidated and compressed during diagenesis into the form commonly seen today.

2 responses

  1. Doc, you’re getting all sciencey… That’ll only confused the ardent theist.

    3 January 2013 at 2:44 pm

    • Ha! John, sometimes you just gotta!

      3 January 2013 at 4:24 pm

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