This is a re-blog of an article which was first posted on this site in April 2012. Like most of our “Skeptics Guides” it was based on a Vic Skeptics discussion pamphlet. The full range of our discussion pamphlets can be downloaded in .pdf form by clicking the “useful info” link here or at the top of the page.
When naturalists started examining the Earth in the 18th century for evidence of its age, they were to a large extent seeking to confirm the suggestion of the Bible that the Earth was several thousand years old; but the closer they looked, the less certain they were that this was the correct answer.
Geologists examined the rocks across Britain, and noted that the same sequence of rocks occurred in different places, suggesting that the rocks had a common source. They also noticed that different levels of rocks contained different groups of fossils, including fossils of animals different from those of today, and not mentioned in the Bible. Yet the fossils were in similar orders in different locations. Rocks were also classified according to how they were made, and by the order in which they’d been created. In the first case, rocks were classified as sedimentary, igneous or metamorphic. Sedimentary rocks are rocks created by grains of mud or sand laid down over the years on lake or sea floors, and compressed into rock by the weight of material lying above them. Igneous rocks are rocks of volcanic origin. Some are from lava which has cooled solid on the surface of the Earth (such as basalt), while others have cooled while still inside the Earth (such as granite), and emerged after they’d solidified. Metamorphic rocks are rocks (usually sedimentary) which have been altered by heat or pressure (such as limestone being converted to marble). Read the rest of this entry »