The two main elements of any theory attempting to reconcile the Bible with legitimate geological data consists of answering two questions: (1) has all life originated from one life form and evolved into all the forms we see today and (2) is the earth/universe young (a few thousand) or is it old (billions of years)?
Modern science does not allow the admittance of the supernatural into its thinking. It postulates mysterious evolutionary forces acting by purely natural means over billions of years account for the origin of all life.
Christians are divided in their thinking relative to origins. Four basic lines of thought summarize their beliefs:
Theistic Evolutionists say modern science and the Bible don't contradict because the Bible is not meant to teach us anything regarding science. God directing the evolutionary processes is all that is needed. (This concept relegates biblical revelation about Creation to mere story-telling.)
Progressive Creationists see the lack of evidence for evolution beyond changes within the original "kinds" of life. But, they accept an ancient age for the earth/universe. The geologic record with its various fossils is interpreted as evidence of God slowly adding various kinds of life on the Earth over millions of years. (This interpretation, however, brings with it some very strange baggage. One example is that ancient remains of man are not really human, but only proto-type experiments before God created Adam and Eve! The Flood is looked upon as a local event with little or no remaining geologic evidence.)
Flood Geology rejects an evolutionary origin for life and has a short chronology. Fossil remains and strata formation are generally cited as evidence for Noah's Flood. (There is no general agreement on where to "draw the line" in the geological record for Flood remains and post-Flood remains.)
Finally, some Christians have come to see that Noah's Flood, while universal and leaving evidence, can't account for most of the fossil record. Some have explained the fossil record as being geologic events since the Flood ended. The CCC model invokes all time-units given in Scripture for geologic events: Creation Week, the long pre-Flood era, the Flood year, and the time since the Flood.