How do fossils form?
Fossils are some of the most remarkable things you can find on Earth! You can learn a lot about what lived before us humans when you find a hunk of sandstone and crack it open! You never know what you might find. Today we will be asking the question ‘how do fossils form?’ in our mini blog post series looking at fossils and dinosaurs!
What is a ‘Fossil’?
So for all those that have just come out of rocks of their own, a fossil is essentially a dead creature that over time lost its flesh and blood leaving only its skeleton behind. Over millions of years this skeleton got covered by soils and as the layers built up the skeleton became hard like the rocks around it and ‘petrified’.
They are uncovered when paleontologists go digging around in rocks to find and study creatures that lived long ago. For example, it's how we know about dinosaurs and how the world used to look during the time they lived. It also tells us that the land around us is always changing and one day we too might be uncovered as fossils in a similar manner.
Fossils are more common than you think and can be uncovered with little knowledge or effort. You just need to ask local experts such as a museum or collectors to give suggestions for the best place to find your own! These can include a coastal area where the sea is eroding a rocky shoreline, the beds of rocky streams, dry deserts like the Grand Cannon, and many more.
So what types of rocks do fossils form in? The majority of rocks where fossils are found are sedimentary. This means that they were loose sediments like soil or sand before they became solid and during this early formation would have easily molded around the dead body of a creature. These types of rocks can include sandstones or limestone.
What Natural Impacts Create Fossils?
A special type of rock that is unique to sedimentary rocks in how they preserve fossils is amber. This glowing distinctive gem is formed through the petrification process of tree sap and a creature is often trapped in it when it first drops from said tree.
Unlike sedimentary rock fossils, the amber is able to preserve not just bones, but the whole organic structure of the creature, although rarely is seen to preserve those larger than a small lizard.
When an amber rock is found it is rough and can vary in color, but when polished it is possible to see what fossils, if any, are contained within without the need to break into rock. This bonus means that some might turn these into beads for jewelry.
A maar is a rare type of fossil depository that exists almost like an unexcavated database of fossil specimens in order of death which give valuable insight into the ecosystem of the region it is found in.
They are formed naturally as low-level volcanic craters which erupt and then fill in with water over time. Then as the ecosystem settles plants and wildlife spring up around it, creating the perfect environment for death and the preservation of all types of fossils.
In New Zealand is Foulden Maar an important site for understanding how the climate of that area existed roughly 23 million years ago with an estimated sequence of layers representative of several thousand years.
Silt and Clay
Larger fossils which we are all familiar with were mainly formed in silt or clay due to their wet consistency and ability to hold exquisite detail of flesh or feathers long after the skeleton is all that remains. Even in their petrified forms, many dinosaurs are surrounded by a ghostly image of what they once would have looked like.
How Old is a Dino Fossil?
So how do Paleontologists know how old a fossil is if it is contained in a small rock without a context? They can use some special dating methods to make guesses about the specimen, or use previously found fossils to make guesses.
Dating fossils has become easier with the rise of complex technologies. One of these is radiometric dating which essentially records the natural radioactive decay of elements such as potassium and carbon to date the time of death.
Dating Dino Death: K-T Event
The K-T event, which occurred 66 million years ago, is attributed to the fall of dinosaurs when a massive meteor hit the planet and destroyed up to three-quarters of plant and animal life. Those that did survive would have been impacted by a darkening of the sun and fighting through the debris of a fiery hellscape.
A lot is known about this event based on a consistent sedimentary layer that is found all over the world and can be used to help date fossils roughly to before or after the said event based on if they appear deeper in the ground or after. They also discovered this theorized meteor impact site in the 1990s which is coined the ‘Chicxulub crater’.
Why Fossils are Important?
Fossils are important because they tell us what lived on the planet before our own species came into being. They also help us understand that the world is always changing and did not always look like it does today.
And dinos are cool so that should be reason enough why fossils are too!
Final Remarks: Fossils and the T-Rex!
The coolest fossil by far is dinosaurs. It's a fact a child knows more about these giant lizards than their own pets. Ask them to name five and they would be able to tell you with their eyes shut. Then of course they would say the T-Rex is the king of them all!
At Thorum we too LOOOOOVE these great carnivores that roamed the Earth 66 million years ago and so we wanted a unique ring to fit this deal. So we acquired some t-rex fossils of our own and greeted some unique ‘dino-themed’ bands as part of our collection.
You can check out these fossil bands as: T-Rex Ring | Thorum