Fossils are what is left of
prehistoric life forms. They are usually saved under a lot of
hard layers of rock. Fossils help tell the story of life dating
back to about 3.5 billion years ago. The study of fossils is
called Paleontology.Geological Time & Ancient Life Forms:
No, we don't mean your parents!
Fossils are what is left of
prehistoric life forms. They are usually saved under a lot of
hard layers of rock. Fossils help tell the story of life dating
back to about 3.5 billion years ago. The study of fossils is
called Paleontology.
Most fossils are found in sedimentary rocks. A few fossils of entire plants or animals have been saved in ice, tar, or sap. Fossils can be the whole or smaller parts of an organism's body. They can be from a plant or an animal. Trace fossils are different marks left in rocks by the activities of these organisms. These can be burrows, animal droppings, tracks and trails. Small fossils, some very small, have to be measured in micrometers or millimeters. These very tiny fossils are called micro fossils. The study of micro fossils is called Micropaleontology. Fossils that can be measured in centimeters or meters range are called mega fossils. The earliest mega fossils we know about are 1to 3.5 billion years old. These fossils were formed in shallow water from blue green algae.
Because of plate tectonics, continents have floated far away from where they were originally. At the end of the 17th century, Englishman Robert Hooke found a fossil of an animal that didn't live during his period of time. He wondered if the animals had changed since a long time ago.
Then, about 150 years ago, some English workmen began to dig up rocks from the ground because of construction. They found fossils. The fossil belonged to what they called the "terrible lizard". We now call them dinosaurs!
The work of early geologists William Smith, James Hutton and Charles Lyell helped us to understand that rocks pile up as layers called strata with the oldest at the bottom and the youngest on top. That knowledge help us to understand about the ages of rocks.
Paul Knipping and Walter Friederich used x-ray diffraction in 1912 to learn about the internal atomic structures of crystals. This means they x-rayed rocks to see how the crystals formed and how long it took for them to develop.
Paleontologists have named eras in the geological time scale. They began with the Precambrian which are the ancient rocks. (There are some well- preserved bacteria and blue green algae found at the north shore of Lake Superior.) Second is the Paleozoic, which is where you find the water invertebrate life and some of the later plants. The third era is the Mesozoic, where new water life and reptiles were found. Fossils of jellyfish, horseshoe crabs, and the first reptile, the pterodactyl, have been found in southern Germany. Also, in the Mesozoic era, dinosaurs and some water animals became extinct. The final era is the present era in which we live called the Cenozoic era. Of course, we share it with many mammals, insects, and flowering plants.
To break down the fossil time line even further, there are five different periods dating fossils. The oldest is the Cambrian, where the first skeletal invertebrates were found in sediments dating 570 million years ago.
The Ordovician period is the second oldest dating 425-400 million years ago. Paleontologists found that land masses were getting higher and there were more plants.
The Devonian period found sharks, forests and the first primitive insects and amphibians. We still have some of these animals and sharks today!
The last period was the Carboniferous period. It is known for producing coal and reptiles. That was about 345-280 years ago.
Over the years, better instruments have been used and each study has improved the information on geology.