How to Find Fossils
Extracting Fossils from Stone
What Are Fossils?
Fossils are the mineralized remains of ancient animals, insects, or plants. They are not the actual bones of the creature, as bones are living tissue and will rot away over time. When people refer to “dinosaur bones,” they really mean the fossilized bones of a dinosaur (though vascular tissue has been found inside some fossils). Bones and shells which undergo fossilization have had minerals seep into the pores – the bones have essentially turned to stone. Very few animals or plants become fossils, as the conditions have to be just right for a fossil to form. A creature must die and become covered in sediment (mud), and not completely rot away before the fossilization process occurs.
How Fossils are Formed (Video)
How do Fossils Form?
380 million years ago, a small crustacean called a trilobite was swimming in a warm, shallow ocean near the equator. The animal died, and fell to the bottom of the sea. Mud and silt slowly accumulated over the animal, and as the layers of sediment increased, pressure was placed onto the animal’s exoskeleton. Minerals from the water were forced into the pores of the skeleton by the pressure, until the bone tissue was entirely replaced with minerals – the animal’s exoskeleton was effectively turned into stone.
Fossils need three basic elements to form: sediment, minerals (typically found in water), and pressure. A great deal of luck is also needed – the great majority of deceased animals and plants simply rot away and do not become fossils.
Types of Fossils
Trace fossils are evidence of an animal’s existence. Footprints or an impression of a shell in a rock are examples of trace fossils. Trace fossils give scientists a lot of information about the way an animal moved and lived. By looking at a dinosaur’s footprints, the speed of the animal, its social behavior, and it’s mode of locomotion may be deduced.
Plant fossils are all around us. Coal is a fossil fuel – coal is the fossilized remains of land dwelling plants. Some coal still bears the imprint (trace fossils) of leave patterns. Methane and one source of natural gas (type III kerogen) are also fossil fuels derived from plants. An impressive example of fossilized plants lies in Arizona – the Petrified Forest contains the remains of ancient trees, forever preserved in the form of stone on the desert floor.
Oceanic fossils can be found in surprising places. Upstate New York has a large deposit of fossilized shells and fish. The large number of shells found in the shale of canyon walls is explained by ancient geography: this area of the United States was located near the equator and was submerged by a shallow sea in the Devonian era.
Dinosaur Fossils are found throughout the world, and are fascinating finds. The hilly area near the Rocky Mountains in the United States has a high density of dinosaur "bones." The badlands of Montana and Wyoming have had a lot of weathering, allowing sediment from the Cretaceous Period to become exposed.
Geologic Eras and Types of Fossils
Trilobites, worms, sponges, brachiopods.
Massive explosion in biodiversity in this era.
Corals, trilobites, jawed fishes, ferns, and early amphibians.
Continent of "Euramerica" existed; early formation of the Applachian Mountains.
Large trees, winged insects, amphibians, and first reptiles.
Highest atmospheric oxygen levels in Earth's history.
Archosaurs, first mammals, ammonoids, and ichthyosaurs.
The Andean Mountains begin to form.
Dinosaurs, small mammals, conifers, and cycads.
Carbon dioxide 4-5x higher than today's levels.
New typs of dinosaurs (Tyrannosaurus Rex, e.g.), flowering plants, sharks, and primitive birds.
Rocky mountains begin to form, CO2 concentration reaches present-day levels.
Extinction of the dinosaurs, modern plants appear, large mammals appear.
Asia collides with India, creating the Himalayas.
Tips for Removing Fossils from a Rock
Once fossils have been identified inside a piece of sedimentary rock, the next step involves removing them from the rock. Sometimes this is an easy process, and other times it is quite tricky. Some fossils are very sturdy (such as ancient sea corals or brachiopods), and other times they are quite fragile (like trilobites). The best tools for removing fossils from the surrounding rock are:
· A hammer
· A chisel
· A stiff paintbrush
· Eye protection
Stand the slab of rock on end, using another rock as a support. Gently tap the end of the rock with the hammer and chisel, until the layers separate. Many times, the fossil will pop out of the rock when this happens. Other times, the chiseling and hammering will require more time to remove the rocky layers from around the fossil.
Take care with fragile fossils – sometimes it is not possible to completely remove the rock from the edges of the fossil. Many people have tried to get that one extra piece of stone away from the edge of a trilobite fossil, just to crack the entire fossil and ruin it.
Sturdy shoes and eye protection are also good ideas for fossil hunting trips. Pieces of shale or limestone can go flying once they are struck with a hammer!
Preserving Delicate Fossils
Some fossils, such as trilobites, are extremely fragile. A simple protective solution of white glue (such as Elmer's glue) and water can be mixed in equal proportions. Simply paint the outside of the fossil with the glue/water mixture and allow it to dry. This will give the fossil a shiny appearance, and the glue will form a protective layer over the delicate exoskeleton.
Penn Dixie in Hamburg, NY
Where to Find Fossils
Most fossils are found in sedimentary rock. Sedimentary rock includes shale, limestone, and sandstone, among others. Sedimentary rock is typically found in layers and is fragile – it will break apart fairly easily and may sometimes be scratched by a fingernail.
Look carefully along canyon walls and near stream beds – the walls may contain sedimentary rock, and many fossils may be hidden within the layers. Gently pull out a piece of stone and inspect it for shells, leaf prints, or other fossilized remains.
Some areas of the world have a high concentration of fossils. Some of the locations are surprising – the Himalayas have a high concentration of fossils. Fossils can be found in every country, and the United States is filled with fossil beds. Every state in the union has fossils that can be found – some have dedicated dig sites that allow visitors to chip away their own fossils and keep what they find.
Locations of the Best Fossil Dig Sites in the United States
The fossil safari at Warfeild Fossil Quarry in Thayne, Wyoming, is a great dig site for families.
U-Dig fossils in Utah has a rich deposit of trilobites.
Penn-Dixie was once the site of a cement company. This fossil dig site has an incredibly rich bed of Devonian era fossils.
Fossil Expeditions in Florida features fossils from sharks, mammals, and reptiles. Kayak excursions are available.
Mineral Wells is a free park where fossil hunters may keep what they find. Brachiopods, trilobites, and crinoids may be found here.