The Flood of Noah’s day (2348 BC) was a year-long global catastrophe that destroyed the pre-Flood world, reshaped the continents, buried billions of creatures, and laid down the rock layers. It was God’s judgment on man’s wickedness and only eight righteous people, and representatives of every kind of land animal, were spared aboard the Ark.
The church taught me that the flood happened approximately 4,500 years ago. Floods happen with some frequency even today, so the changes they make to the landscape, geology, etc. are all well known. The story of Noah also tells us that every animal on the planet was reduced down to only a single mating pair (or seven pairs for the clean animals), so what evidence have we found today to demonstrate this loss of animal life? We would also be able to see catastrophic destruction of all human life save Noah and his family. If a global flood happened thousands of years ago, we should be able to find proof of that in either seeing entire civilizations of people disappear in an instant all at the same time. Or perhaps we can track certain plants that all would've died at the exact same time.
Dendrochronology
From childhood we are taught that the number of rings in a tree tells us how old a tree is. The changing of seasons causes the tree to grow faster or slower depending which become visible rings in a tree trunk. The study of this phenomenon is known as "dendrochronology.
It's possible to not just measure the age of tree with its rings, but you can also figure out which years the tree was alive for. This is possible since tree ring size is based on the length of a season, all trees in a particular area will have the same tree ring pattern. So it's possible to create a database of tree ring patterns and figure out when a particular tree you are looking at lived.
By digging up older trees and analyzing the ring structure, researchers have been able to string together over 12,000 years worth of unbroken tree rings. Meaning, that there have been trees existing and living without any break for at least the past 14,000 years.
No tree could survive being underwater for half a year. So if God killed every living thing, how is that there are no breaks in tree rings for the past 14,000 years? Why don't we see a sudden break 4,000-5,000 years ago when all the trees should have died and then reappeared a number of years later starting a completely new chain of tree ring history?
Zoology
It is estimated that there are about 6,500 species of land mammals alive today. There's at least another 7,000 species of reptiles as well. However, Answers in Genesis claims that the "worst-case" scenario would involve Noah caring for 7,000 animals.
Even if we are only considering mammals and reptiles, then we're talking about Noah caring for close to 30,000 animals. Not only could the boat not fit that many animals, but the handful of people on the boat would not be able to feed or take care of that many animals or even come close to storing the amount of food required for everything on board.
We also have at the time when this was supposedly happening, living Wooly Mammoths in northern Russia. But also how do animals that only live on a single island redistribute themselves after the flood? Komodo dragons are only found on near Indonesia; the Galapagos turtles found only on those islands; or any other number of animals that are only found in single locations.
If Noah's flood happened, then how do we explain the large diversity of life today that could not possibly all fit on a boat? How did the animals all disperse to the correct locations and make journeys of 1000's of miles both there and back?
source: Aron Ra