How Does a Plant Become a Fossil?
Fossils help scientists understand how life may have been millions of years ago. While we've all heard of animal fossils, especially those of prehistoric humans and dinosaurs, you may not have heard as much about plant fossils.
Most plants have very thin leaves and other structures that make them more difficult to fossilize than hard bones. But luckily for science, it is possible.
In order to fossilize, a plant needs to be buried under fine dirt, sand or mud particles--also called sediment--before the plant's tissues have a chance to be attacked by fungi or bacteria or to disappear completely due to decomposition. The plant also has to be buried with little force; if it's buried forcefully, it will simply break apart.
Certain plant types are easier to fossilize. Sturdy, fibrous and waxy plants have structures that hold up well under physical pressure and over time. There are several methods of plant fossilization.
Impressions
This type of plant fossilization leaves behind no cells of the plant's tissue. All the water that was in the plant is pushed out because the sediment is on top of the plant. An impression of the plant is left behind, but under the scrutiny of a microscope, there will be no actual plant material. Even so, there can be a lot of detail in the impression, at times down to the cellular level. The most valuable information from impressions is the external shape of the plant.
Compressions
Similar to impressions, plants fossilized in this way are usually flattened by the sediment. The primary difference between impressions and compressions is that there is some organic plant material left behind because the plant was "protected" by a layer of carbon--that is, they are basically turned into coal.
Casts and Molds
Trees are often fossilized in their three-dimensional form. A cast is formed when sediment fills up a space that was occupied by now-decayed plant material, whereas a mold is the cavity itself, unfilled. Organic material is usually not part of a cast or mold.
Permineralization
This rare type of plant fossilization is what creates petrified wood. Under very specific circumstances, usually involving volcanic ash, the organic parts of a tree are literally turned to stone through chemical processes. Minerals replace the once-living cells and membranes. This type of fossilization generally provides the most detail.
Tags: plant fossilization, plant material, Become Fossil, left behind, Plant Become, Plant Become Fossil
