Discovering Fossils and Dinosaurs at Construction Sites

Most people think of dinosaurs when they hear the term “fossils.” Fossils actually encompass all creatures that left some sort of preserved remains when they died. The process of fossilization is an important part of understanding natural history. Fossils are often discovered at construction sites when large quantities of dirt are moved and long-buried rocks and other natural debris are uncovered. Sometimes, these discoveries aren’t noticed until it’s too late to preserve them, but construction workers who pause work and alert the necessary authorities are hailed as heroes within the scientific community.

What Is a Fossil?

fossil is the preserved trace or remnant of something that was once living. Fossils can be left behind by either plant life or animals. Dinosaur bones, the most famous kind of fossil, are body fossils. Trace fossils are fossilized evidence of a creature’s life, such as a preserved footstep. Construction site finds that make the news are usually body fossils. Trace fossils are more likely to be discovered by professionals or people actively looking for fossils.

How Are Fossils Formed?

Fossils are formed when the remains of a plant or animal are buried quickly in the right climate conditions. In these cases, fossils can form. There are five different types of fossils, and each forms in its own specific manner.

Types of Fossils

Different types of fossils include stone fossils (also known as mold and cast fossils), whole animal fossils, and petrified wood. The types of fossils are categorized by what sort of animal or plant left the remains behind or by how the fossil was formed. Stone fossils and whole-body fossils are the types most often found at construction sites.

Mold and Cast Fossils (Stone Fossils)

Mold and cast fossils are made when an animal dies and ends up in a riverbed. The flesh either deteriorates or is fed on by smaller creatures, and what’s left is covered by a mix of mud and sand, called sediment. Over time, these layers of mud and sand form into hard rock. The remains decay or dissolve and are washed away, and what is left is a natural mold. Eventually, the entire mold becomes solid rock, which is pushed to the surface when the ground is disturbed by earthquakes or human-caused occurrences, like digging for construction projects. Paleontologists also dig through undisturbed ground to locate fossils.

Whole Animal Fossils

Entire animals, like the woolly mammoth, have been found preserved and intact because their corpses were trapped in ice for millennia. Although not everything leaves behind a fossil, some of the smallest creatures in the world have been found completely fossilized. Insects are another common whole-animal fossil. Often, insects would become trapped in tree sap, and this sap turned to amber over time. Insects from millions of years ago have been found preserved in amber, looking much like they did when they were alive.

Petrified Wood

Petrified wood is made when wood turns into stone. Scientists don’t entirely understand the process, but it’s likely that it happens when oxygen is absent during the decaying process after the death of the tree. The remains are then buried in a riverbed, much like the process for stone fossils. The water contains minerals that work into openings in the wood, and these minerals serve to preserve the wood and fossilize it.

How Long Do Fossils Take to Form?

The formation of fossils typically occurs over millions of years. However, fossils formed in ice can form in just centuries.

Where and How Are Fossils Discovered?

Fossils are located in a wide variety of places. They are discovered by paleontologists, amateur fossil collectors, and construction crews preparing the ground for new buildings or roads. Sometimes, natural ecological processes like earthquakes uncover fossils.

Near Water

Sedimentary rocks are formed in swamps, lakes, oceans, and rivers when materials like mud, clay, and sand slowly harden over the course of millions of years. This means that many fossils are found near bodies of water or in places that were once in or near bodies of water. The first dinosaur fossil discovered in North America was found by Ferdinand Vandeveer Hayden in 1854 while exploring the Missouri River. Sometimes, fossils are used to provide historical information about the ecology of an area.

In Ice

Ice fossils can include animals and humans. The oldest human remains were found in the Alps in 1991. The remains were fully frozen. Meanwhile, entire wooly mammoths dating back to the Ice Age have been found in the tundra in Siberia.

In Forests

Whole-body insect fossils are typically found in forests because amber was usually formed on trees. A Mexican miner found a 25-million-year-old tree frog in amber in 2005. Trace fossils are also commonly found in forests, along with fossil trees.

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