Okay, so I didn’t know this was a thing, but I found out there is a National Fossil DayTM here in the States. It’s the Wednesday of Earth Science Week in October.


Now that is my kind of holiday. The idea behind it is to show how much we can learn about the past (and possibly predict about the future) from fossils and the need to understand and preserve them.


The National Park Service has some great art and articles as well as a list of related events-check to see if there’s anything going on in your area!

Ray Troll's strata.

Ray Troll’s strata.

(The US and UK have Earth Science Week at the same time: here’s the Geological Society for those who want to check out events across the pond)


The NPS also have a really interesting list of National Parks preserving fossils and rocks arranged by geological era.


A snippet of Ray Troll's state fossils.

A snippet of Ray Troll’s state fossils.

Did you know most states have designated state fossils? What’s your state fossil? I did know, but still feel mildly cheated since they’re Jurassic era footprints. Apparently our geology is more suited to cast fossils than replacement fossils.


There are several different types of fossils. The dictionary defines fossil as “any remains, impression, or trace of a living thing of a former geologic age, as a skeleton, footprint, etc”


Permineralized (petrified) fossils are what most of us think of when we think of fossils. They form when minerals slowly replace organic matter, so the entire thing becomes stone. (So they’re also called replacement fossils.) Think petrified wood and dinosaur bones. Most of the fossils I work with are permineralized fossils. Here’s a somewhat messy project that illustrates the idea!


Mold and cast fossils are the most common type of fossil. Many of them are trace fossils which are preserved traces of animals-like my state’s dinosaur footprints, tooth marks, nests, burrows, even tail marks. These fossils are not actual parts of the animal. A mold is when something is pushed into something soft and leaves a hollow or impression. The cast comes in when ash or sediment fills the mold. Another messy fossil project for molds and casts!


Preserved remains or body fossils are when the organisms’ whole body is preserved-like an insect in amber or a mammoth in ice.


Compression fossils form when an organism is under extreme pressure. It leaves behind a dark imprint. This is the most common type of leaf fossil found. It’s also what you probably think of when you think of fish fossils. (If you do such a thing.)

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