Fossils, Climatic Changes, and Mineralization Help

Climatic Changes

Another factor in fossil scattering, besides tectonic movement, is the changing climatic cycles. Over geological time, the level of the oceans has risen and fallen many times. The water overflows the land and then drains off again. While this is going on, the climate is also heating up and then cooling down again. The world and its citizens enjoyed hot and muggy conditions during some time periods and cold and freezing conditions during others.

Some climatic changes were worldwide, while others affected some landmasses more than others, depending on location. If a continent originally located at the equator drifted northward over a geological time, then its resident plants and animals would have to change to survive.

Geologists believe that there have been four major periods of glacial activity during the time that most fossils were deposited and transformed into rock. The first of these took place in the Precambrian era and before. It is estimated that the Precambrian represents 88% of all known geologic time. It is divided into the Hadean (beginning), Archean (ancient), and Proterozoic (early life) eons. The Phanerozoic eon (visible life) is the youngest eon with the best fossil and rock record. The majority of what paleontologists study today is from the Phanerozoic. The different eons, eras, periods, and epochs can be a bit confusing. .

The second glacial phase happened late in the Ordovician (Phanerozoic eon, Paleozoic era). The third important glacial age took place during the Carboniferous to middle Permian time, estimated at around 20 million years. During this deep freeze, the southern hemisphere, containing (bunched together at that time) South America, Africa, India, and Australia, was one big polar ice cap.

During the melting of this ice chunk, huge amounts of water flooded existing primeval jungle; plant, amphibian, and insect habitats. Fossil sedimentary rock layers contain these types of inhabitants along with the marine organisms that were carried in by the flood waters. The final glacial period began in the Pleistocene period (around two million years ago) and continues on today.

Thorough study and radiometric dating of fossil pollen, organisms, and surrounding rock have made finer glacial time divisions possible. Now geologists believe that there may have been greater than 15 periods of glacial ebb and flow. These periods included warmer climates with thriving, diverse species found throughout. However, geologists are finding that a richer line-up of species are found during times of various temperature changes and glacial cold.

Species, alive at various periods in the Earth’s history, had to adjust to climatic changes during their lifetimes. The strongest passed on their genetic information to their offspring who lived other lifetimes. Table 10-1 gives you an idea of the dinosaur record holders that have been discovered.

Table 10-1 Paleontologists are always looking for the next unique fossil discovery.

Time is the key to change. Think of it like surviving a volcanic eruption. The more time you have to get away, the better your chances of survival. This is one of the problems that species on the endangered list face today. Their habitats are changing (sometimes eliminated completely) within a few short years and mostly they don’t have time to adapt or escape. That is why it is important if we are to preserve plant and animal species for future generations for people to take a hard look at how the development of natural areas affects native species and habitats in the area.