Don't get me wrong; the world does appear to be older than the 6000 years deduced by Bishop Usher. Nonetheless the billion-year figures you see in geology books do not appear to be on any firmer ground than the bishop's calculations were.
Varves are one example of the problems involved.
A vew examples:
Some thick and extensive sedimentary layers have remarkable purity. The St. Peter sandstone, spanning about 500,000 square miles in the central United States, is composed of almost pure quartz, similar to the sand on a white beach. It is hard to imagine how any process, other than global liquefaction, could achieve this degree of purity over such a wide area. 16 Almost all other processes involve mixing, which destroys purity.Streams and rivers act on a small fraction of the available sediments and deposit them along a narrow line, but strata are not linear features. Liquefaction during the flood acted on all sediments and sorted them over large areas in a matter of weeks or months.
Sedimentary layers usually have boundaries that are sharply defined, parallel, and nearly horizontal. Thin, sharply defined layers are sometimes stacked vertically, thousands of feet deep. If each layer had been laid down thousands of years apart, erosion would have destroyed this parallelism. Again, liquefaction explains this common observation...
Varves are extremely thin layers which evolutionists claim, without much justification, are laid down annually in lakes. By counting tens of thousands of varves, they believe elapsed time can be determined. However, since varves are so uniform, show no evidence of the slightest erosion, and are deposited over wider areas than tiny "stream deltas," they are better explained by liquefaction. PREDICTION 14: If representative corings are taken in the bottom of any large lake, they will not show laminations as thin, parallel, and extensive as the varves of the Green River formation....
Fossils not formed by gradual processes:
Dead animals and plants quickly decay, are eaten, or are destroyed by the elements. Their preservation as fossils requires rapid burial in sediments thick enough to preserve their bodily form. This rarely happens today. When it does, such as in an avalanche or a volcanic eruption, the blanketing layers are not strata spanning hundreds of thousands of square miles. Liquefaction provides a mechanism for the rapid burial of trillions of fossils in appropriate layers. A similar statement can be made concerning fossilized footprints and tracks of many animals. (See also 21. Rapid Burial on page 7 .)...
The absence of meteorites in deep sediments is consistent only with a rapid deposition of all the sediments. (See 77. Shallow Meteorites on page 28 .)...
Almost all animals are directly or indirectly dependent on plants for food. However, geological formations frequently contain many fossilized animals without fossilized plants. 17 How could they have survived? Apparently the fossilization process involved a sorting that treated plants and animals differently....
The article neglects to mention that a global flood could wash animals into basin areas for burial while plants and trees, having roots, would be somewhat harder to wash away or might take longer to uproot and then get washed into other areas. Like I say, the entire general approach taken by geologists does not appear to be on solid ground.