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.

• Scientists Say Dinosaur Fossils Found in Colorado Are Those of a 68-Million-Year-Old Triceratops
• Construction Crew That Found Triceratops Fossils Considered “Heroes”
• Rare Triceratops Fossil Discovered at Construction Site
• Construction Crews Dig Up Dinosaur Fossils in Colorado
• Construction Reveals Trove of Fossils in Carlsbad

What Is a Fossil?

A 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.

• What Is a Fossil?

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.

• How Do Fossils Form?

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.

• Different Kinds of Fossils

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.

• Petrified Sea Gardens

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.

• How Earth’s Oldest Animals Were Fossilized

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.

• Petrified Wood

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.

• How Can I Become a Fossil?

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.

• How Are Fossils Discovered and Collected?

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.

• If Rocks Could Talk: Limestone

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.

• Siberia Permafrost Yields Well-Preserved Ice Age Woolly Rhino

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.

• Oldest Known Fossil Forest Discovered in Cairo, New York

Dinosaurs, Paleontology Studies, and More

• • The Dinosauria: The University of California, Berkeley gives information about what a dinosaur is and what a dinosaur isn’t in this guide to understanding the terminology.
  • The Mesozoic Era: Dinosaurs lived in the Mesozoic Era, which includes the Triassic, Jurassic, and Cretaceous periods.
  • Decolonizing the Hunt for Dinosaurs and Other Fossils: Searching for dinosaur fossils has often followed the colonization of other countries.
  • Dinosaurs’ Living Descendants: Although dinosaurs are extinct, their descendants evolved into birds.
  • Dinosaur National Monument: The Dinosaur National Monument in Colorado provides an excellent chance to see fossils up close and walk where dinosaurs once roamed.
  • Giants of the Mesozoic: The Fernbank Museum re-created the largest dinosaur fossils ever found and displays them as a permanent exhibit. The models for these fossils were discovered in Argentina.
  • Dinosaur-Lovers Descend on the Smithsonian’s Newly Renovated Fossil Hall: The Smithsonian’s Fossil Hall includes a T. rex fossil that is 66 million years old and exhibits centered on placing the history of the dinosaurs in the broader history of Earth as a whole.
  • How Many Kinds of Dinosaurs Were There? The field of paleontology is constantly making advances in finding and naming dinosaurs, meaning that there are many more kinds identified today than there were when most adults learned about dinosaurs as children.
  • Dinosaurs: An informative fact sheet gives information about the different kinds of dinosaurs, how they are classified, and what happened to the dinosaurs.
  • Drexel Team Unveils Dreadnoughtus, a Gigantic, Exceptionally Complete Sauropod Dinosaur: Scientists discovered a new 85-foot-long dinosaur they’ve named the dreadnoughtus, which has 70% of its skeleton intact.
  • “Reaper of Death”: New Species of Tyrannosaur Discovered in Canada: A newly discovered tyrannosaur species named the thanatotheristes degrootorum shows the evolution of the T. rex into an ever more efficient predator.
  • Ten Best Recent Dinosaur Discoveries: Recent finds include a diverse array of creatures that shift the understanding of what dinosaurs were away from the image of scaly, reptile-like creatures.
  • New Species of Burrowing Dinosaur Found Perfectly Preserved in China: A small fossil dating back 125 million years was found in what researchers dubbed a “Cretaceous Pompeii,” a formation that appears to have trapped many animals under the remnants of a volcanic eruption.
  • What Is the Difference Between Paleontology and Archeology? This article explains the differences between two somewhat interconnected fields.
  • New Paleontology Guidelines Enforce Ethics, Reproducibility: Ethics and ethical behavior are important parts of scientific work. Paleontology is adapting to ensure the field remains ethical and the work of scientists in the field adheres to best practices.
  • Scientists Have Found the Oldest Known Human Fossils: Humans are also part of the fossil record, and the discovery of human fossils can change what archeologists, historians, and anthropologists believe about the earliest humans.
  • A Timeline of Fossil Discoveries: The first recorded fossil discovery dates back to the mid-19th century.
  • Oldest Human Fossils Found: NPR reports on human fossils found in Africa.
  • Trace Fossil Gallery: The University of Wisconsin-Madison offers information on and a gallery of various trace fossil types.