Flood geology is the study of the Earth's geology from the point of view that the Earth's geology was radically redefined by a global flood in the relatively recent past, as recorded in Genesis, as well as the scores of flood stories in other cultures throughout the world.
Genesis Flood account
Genesis provides the most detailed account of the global deluge, including specific dates, measurements, and even some key geological events during the flood. Consequently, flood geologists use it as a starting point for understanding the events of the deluge. Based on the Genesis account, flood geologists argue that the flood resulted from subterranean water erupting to the surface ("the springs of the great deep burst forth" ), combined with 40 days and nights of rain. Although the rain stopped after 40 days, the flood waters continued to rise for 150 days, and lasted just over a year before Noah and the others on the boat were able to leave. During the flood, there was massive tectonic activity, including some land rising up and other land dropping, such that the waters ended up in newly-deepened oceans. All the animals and birds (except those on the ark), and large numbers of sea creatures perished, and many of them were buried so quickly that they became fossils, accounting for the vast majority of fossils existing today.
Flood geologists base their belief in a relatively recent global deluge on several strands of evidence. While none of these strands alone is sufficient to prove that a global flood occurred, flood geologists argue that a global deluge is the most reasonable and parsimonious explanation for the evidence.
Sedimentary rocks are formed by sand and other sediments which settle out of suspension in water, minerals which dissolve in water (which sand cannot do) and the hard parts of small aquatic organisms such as plankton, which accumulate on the bottom of a body of water and undergo lithification. Although only about 8% of the earth's rocks are sedimentary, 75%-80% of the Earth's land area is covered in sedimentary rock. Therefore, geologists point out, there is irrefutable evidence that at least 75% of the Earth's land was once covered in water.
There is enough water on Earth today to cover the entire surface to a depth of 2.7 kilometres (1.7 miles), if the surface was levelled out. Continents emerge because the average ocean depth is 3.7 km.. Flood geologists argue that geological activity during and after the flood lowered the ocean basins, causing water to flow from the continents into the basins, and leaving dry land.
Fossilization requires rapid burial in a sedimentary solution, and subsequent rapid lithification of the solution. Slow burial does not result in fossilization, because the remains decay prior to being fossilized. Therefore, every fossil was buried in rapidly deposited sedimentary material which subsequently turned to stone.
Fossil fuel formation requires the burial of enormous amounts of organic matter under a sedimentary solution, and the application of heat and pressure. Slow burial processes do not produce fossil fuels, because the organic matter decays prior to conversion into a fossil fuel. Therefore, all fossil fuels on earth were quickly buried under sedimentary material which subsequently turned to stone;
Most sedimentary rocks are layered, forming sharply defined lines at varying depths. Were these formed over long periods, erosion would have softened these lines. The sharpness of the lines implies rapid deposition and lithification.
Pure sedimentary layers
If sedimentary layers were laid down over millenia, they would have experienced mixing. However, many rock strata are pure -- for example, the St. Peter Sandstone, covering 500,000 sq miles of the United States, is 99.94% pure silica. While uniformitarian scientists state that it was deposited by the shore of a sea, they cannot explain how it remained so pure if it was laid out over a long period of time. However, the sorting processes of liquefaction, consistent with a global flood, can make such an explanation.
Canyons can be found under the sea at the end of many major world rivers, including the Congo, Amazon, Ganges, and Hudson. They extend for thousands of miles underwater, thousands of feet under the sea; they are as deep as the Grand Canyon in places, and although not well understood by the mainstream scientific community, they are generally understood to have developed when sea-levels were significantly lower than today. Flood geologists argue that as the continents divided and the flood subsided, these major rivers drained the new continents, and the water flowed into the new low-lying areas, which would fill to become seas, leaving the sediments to dry out of their liquefied state.
As explanation for great land canyons such as the Grand Canyon, flood geologists point to canyon formation events such as the catastrophic hot mud slides observed during the eruption of Mt. St. Helens. One particular hot mud slide at Mt. St. Helens carved a canyon 140 ft. deep and 17 miles long in a single day. Only a thin creek remains at the bottom of the canyon today, which would likely be interpreted as having carved the canyon "over millions of years," if it were not known first-hand that the canyon was carved in a single day.
Plato's Timaeus states:
- "In those days the Atlantic was navigable; and there was an island situated in front of the straits which are by you called the Pillars of Heracles [Straight of Gibraltar] ... and was the way to other islands, and from these you might pass to the whole of the opposite continent which surrounded the true ocean; for this sea which is within the Straits of Heracles is only a harbour, having a narrow entrance, but that other is a real sea, and the surrounding land may be most truly called a boundless continent."
A clear problem with a global flood is that of repopulation: after the flood, very few non-marine species would survive. In particular, most of those observed today could not possibly have survived - this includes all insects, the vast majority of birds (Some species of albatross may have survived), the vast majority of mammals, and possibly freshwater fish depending on the salinity of the floodwaters.
Flood geology models include a means for these species to survive, most typically via artificial assistance - an Ark, as described in Genesis.
An often-proposed explanation is that of continental drift - that the continents may once have been united in a single supercontinent, which broke into fragments and drifted into the formations seen today during the time between the start of repopulation and today. Continental drift in principle is nearly universally accepted by all geologists, with flood geology differing only in time: While conventional geology estimates the breakup of the supercontinent to have occurred over approximately sixty million years, flood geologists mostly claim that the process occurred during the flood year, whilst a few claim that it occurred at the time of Peleg.
Flood geologists propose several models which would explain how continental drift could proceed at the rapid pace required to allow the rearrangement of continents during or shortly after the flood, then slow to the currently observed rate. One of the best known of these is the runaway subduction model of Dr. John Baumgardner.
Flood geologists argue that the scale of destruction of the Flood, especially if rapid plate tectonics was involved, would mean almost certain total destruction of the pre-Flood world, including any evidence of civilisations predating the Flood, along with the destruction of the Garden of Eden. After the Flood, and particularly after the Tower of Babel, new civilisations developed, that either survive to this day or that we find archaeological evidence of today.
Flood geologists date the flood to around 2350 B.C., based on biblical chronology. They argue that archaeological dates which purport to show civilisations and artifacts being older than the Flood (see Criticisms) are incorrect because they are based on the presumption that none of these methods would be altered by the effects of a global flood in such a way as to render conclusions drawn from them invalid. Christian apologetists state that the biblical flood would have occurred before the Egyptian pyramids were built and that the commonly cited Egyptian chronology is errant and built upon poor foundations.  Also, Christian apologists argue that ancient Sumerian history supports the flood account given in the Bible.  In addition, ancient Sumerian literature speaks of a world wide flood. 
Explanation of Geological Strata
Advocates of flood geology generally use the flood as an explanation for the existence of the geologic column, and indeed any geological phenomena or feature. It proposes that the age of the Earth as shown by rock strata is only apparently old, an illusion caused by looking at it through a secular worldview. Thus, while a scientist may spend years developing and testing theories through evidence, a flood geologist manufactures evidence to fit his theory.
Fossils follow a logical pattern. The old ones are near the bottom, the young ones near the top. This is cited as evidence that a catastrophic flood could not have occurred, due to the fact that a flood powerful enough to create canyons in 40 days would also disturb the fossils to a point that they are no longer possible to date. Instead, the fossils follow a pattern predicted by evolution, where the fossils follow the pattern of old to young. Similarly, mass extinction events such as the KT boundary provide very fine lines that cut off the fossil record - this is incompatible with the idea that all rock sediment was laid down only a few thousand years ago in a massive flood.
Erosion is a slow process in conventional geology - unless the rock is soft and the weather particularly severe, but these cases are outlying exceptions. This is all due to the hardness of rock and the fact that we can observe the rate that it erodes under rain now. The flooddidit idea proposes that despite this, all erosion features can be explained by the flood. This applies equally to rock that is eroded to rock that isn't eroded - a proposition that flies in the face of both science and good sense. The high levels of erosion seen in hard rock formations is chalked up to the speed of the flood waters. Indeed, fast water can be quite powerful and water cutting jets can slice through objects with high efficiency. However, the Grand Canyon, for example, isn't a small board of MDF being hit by a precise sub-millimeter wide jet of water traveling at hundreds of miles per hour. Even in a flood of global proportions, the water could not travel fast enough (it can only work under gravity) and the rock is simply not soft enough for it to form in anything less than millions of years.
Secondly, erosion due to the flood is incompatible with rock sedimentation being explained by the flood. A global flood that would explain both sedimentation and massive erosion would cause both processes to occur simultaneously. There should be more sediment put down at a near equal rate to the erosion removing it - therefore features where erosion has revealed the sedimentation layers should not exist. Conventional geology is able to explain that sedimentation occurs first and erosion cuts in afterwards to expose the layers, and also explains more distorted features such as uncomformities - which flood geology is unable explain.
Creationist Scientists Defense of Flood Geology
Creationist scientists assert that there are multiple lines of evidence from the field of geology showing that flood geology is correct.  Creationist scientists also state that there was enough water to cause a worldwide flood and various other objections to a worldwide flood are invalid. 
Critics claim that there is not enough water on the Earth to actually cause a worldwide flood, or ever has been; in addition, many archaeological records (notably tree-ring records and the records of various early civilizations, including Egypt and Sumeria) stretch through the period of time most often given as that of the Great Flood, without any actual reference to such an event.
Until the rise of uniformitarian geology in the early 19th century, most geologists accepted the Noahic deluge as part of geology. But James Hutton proposed in 1795 that geology ought to be based on the processes that we see happening now, thereby automatically ruling the Flood out of consideration. During the 19th century a number of "scriptural geologists" held out against the rising acceptance of Hutton's principles, but they fought a losing battle and interest in flood geology virtually died out by the end of the 19th century.
However, in the second half of the 20th century, interest was revived amongst people keen to show that the biblical account was correct, and a small but growing number of geologists are now studying this field again, although the vast majority of geologists still reject the idea of a global flood on Earth. At the same time, there has been a recent resurgence of catastrophism in geological interpretation. 
Interest in Flood Geology was stimulated by the 1961 publication of The Genesis Flood, by Henry Morris and John Whitcomb. Dr. Henry Morris had a number of arguments for geology supporting a worldwide flood. 
- Geology and the Flood by Henry Morris, Ph.D.
- Stratigraphic Evidence of the Flood by Stuart E. Nevins.
- Flood models: the need for an integrated approach by A.C. McIntosh, T. Edmondson & S. Taylor.
- Global Flood Geology from Creation Science Perspectives
- Biblical Geology: Properly Understanding the Rocks
- ↑ http://www.icr.org/article/570/
- ↑ Genesis 7:11, NIV
- ↑ http://pearsonkt.com/summaryStreetOT/texts/Sci-National-Grade-4/iText/products/0-328-34278-5/unitc/ch11/331.html
- ↑ Noah’s Flood—what about all that water?, Chapter 4 of the Creation Answers Book, Dr. Don Batten (Ed.)
- ↑ http://www.mos.org/oceans/planet/features.html
- ↑ Psalms 104:6-9 (NASB) "You covered it with the deep as with a garment; The waters were standing above the mountains. At Your rebuke they fled, At the sound of Your thunder they hurried away. The mountains rose; the valleys sank down To the place which You established for them. You set a boundary that they may not pass over, So that they will not return to cover the earth."
- ↑ http://classics.mit.edu/Plato/timaeus.html
- ↑ http://www.globalflood.org/platetec/about.html
- ↑ One example is Carbon Dating which is calibrated according to known background levels of C14 in the atmosphere, but this calibration does not account for likely altered levels due to extensive volcanism during the Flood. See Carbon dating into the future (Creation Ministries International).
- ↑ http://www.apologeticspress.org/articles/2503
- ↑ http://www.christiananswers.net/q-abr/abr-a009.html
- ↑ http://home.comcast.net/~chris.s/sumer-faq.html#A1.6
- ↑ http://www.icr.org/index.php?module=articles&action=view&ID=381
- ↑ http://www.answersingenesis.org/home/area/faq/docs/tree_ring.asp
- ↑ http://www.biblicalchronologist.org/answers/c14_treerings.php
- ↑ http://www.grisda.org/origins/21066.htm
- ↑ http://www.creationresearch.org/crsq/articles/26/26_1a.html
- ↑ http://www.creationresearch.org/crsq/abstracts/sum29_4.html
- ↑ The following article explains how Christian geologists create explanations for the flood based on the Biblical account, instead of creating theories based on observed evidence like secular scientists do: http://creation.com/flood-geological-maps
- ↑ http://www.answersingenesis.org/home/area/faq/geology.asp
- ↑ http://www.creationism.org/topbar/geology.htm
- ↑ http://www.grisda.org/georpts/gr11.htm
- ↑ http://www.nwcreation.net/geologylinks.html
- ↑ http://globalflood.org/
- ↑ http://www.answersingenesis.org/Home/Area/AnswersBook/flood12.asp
- ↑ http://www.answersingenesis.org/home/area/faq/flood.asp
- ↑ For a summary of other criticisms, see http://www.talkorigins.org/faqs/faq-noahs-ark.html
- ↑ http://www.icr.org/index.php?module=articles&action=print&ID=84
- ↑ http://www.grisda.org/georpts/gr11.htm
- ↑ http://www.icr.org/index.php?module=articles&action=view&ID=54
- ↑ http://www.icr.org/index.php?module=articles&action=print&ID=84
- ↑ http://www.icr.org/article/842/