XXX Chats

Playstation 3 sex chat room names

Radioactive dating isotopes

s the creation/evolution debate continues, there has been an increasing sophistication of certain Creationist arguments and publications.

It can be an especially difficult challenge when the Creationist author has professional credentials and has published in mainstream scientific journals.

One such individual is Robert Gentry, who holds a Master's degree in Physics (and an honorary doctorate from the fundamentalist Columbia Union College).

Gentry has spent most of his professional life studying the nature of very small discoloration features in mica and other minerals, and concluded that they are proof of a young Earth.

Geologists classify rocks into three main categories - sedimentary, igneous, and metamorphic - based on the way in which they form.

Sedimentary rocks are secondary in formation, being the product of precursor rocks (of any type).

Igneous rocks form from molten material, and are further subdivided into two main categories, the volcanic rocks which form from lava extruded at or near the surface; and plutonic rocks which form from magma, deep within the crust.

Both types of igneous rocks comprise a mixture of different minerals.

As igneous rocks cool, mineral crystals form following a specific sequence.The crystals develop an interlocking texture with some of the trace minerals becoming completely surrounded by later forming crystals.Volcanic rocks, because they are able to cool and crystalize rapidly, have a very fine-grained texture; the individual mineral grains are too small to see easily with the naked eye.Plutonic rocks on the other hand cool very slowly, on the order of a million years or more for some deeply buried and insulated magmas.The mineral grains in these rocks can grow very large and are readily distinguished in hand samples.Granite is a well-known type of plutonic igneous rock, but there are many others as well.Geologists distinguish these types of rock based on their chemical and mineralogical composition.Granites, for example, have more than 10% quartz and abundant potassium feldspar.Other plutonic rocks have less quartz and potassium, and different ratios of calcium and sodium feldspar minerals.True granites are relative latecomers on the geologic scene as they required a number of recycles of crustal material to differentiate and concentrate potassium.In an earlier edition of , Lorence Collins (March/April, 1999) provided a thorough overview of the origin and nature of granitic rocks.

Comments Radioactive dating isotopes