Fossils in this issue of NatureWILD
|A trilobite fossil. Photo: Kevin Walsh|
What are they? How are they formed? What do they tell us?
Article and Figures 1,2,3 by Young Naturalist Nick Ward (YNC Burke Mountain).
Fossils are the remains of ancient life that have been turned to stone. They come from plants and animals that died thousands or millions of years ago. Usually only the hard parts are preserved in the fossil, because the soft parts rot away before they can be fossilized.
How do fossils form?
Fossils from animals are created when the hard parts of a dead animal are replaced by minerals. To become a fossil, the animal must have been buried soon after death before it rotted away. (see Figure 1, section A). Over thousands of years, the sediment (fine earth) that covered the organism is compressed into stone. (see Figure 1, section B). The soft parts of the organism like the skin, muscles and other organs will most likely have completely decayed; the bones are all that is left and eventually they are slowly replaced by minerals. (see Figure 1, section C). If the soft parts didn’t rot earlier on, they can also become part of the fossil but this is very rare. (see Figure 1, section D)
With plants the process is different. For plants to fossilize, they need to be buried very quickly because they are all soft tissue. Most of the time the soft tissue isn’t replaced by minerals as with a bone; instead, a carbon imprint is left on the rock. Later, the rock around the fossils may erode (wear away), leaving the fossil imprint exposed to be discovered. (see Figure 2).
What is the fossil record and what can it teach us?
Fossils record the history of the earth from the beginning of life to the present day. We can learn a lot from the fossil record such as – what forms of life existed thousands of years ago and how they evolved, major events of the past, and the behaviour of ancient animals.
The main thing that the fossil record can teach us is about the animals and plants that lived in the past. We can learn what they looked like, where they lived, and in what time period. We can also learn about how ancient creatures evolved. For example, by looking at ancient fossils, we can see how over millions of years, some fish grew legs, lost their gills and evolved into amphibians.
Fossils also tell us about major events of the past. When we see a point in the fossil record where most of the species that we were seeing before are suddenly gone, this tells us that there was a mass extinction (die off). If we find a large heap of fossils this could mean that there was a flood that piled them together.
We can also learn something about the behaviour of ancient animals from fossils. If we find lots of different types of fossilized footprints leading to and away from a certain place, we can guess that that was a water hole. We can look at fossilized droppings to tell what the animal ate. If we find an animal very close to its nest, it may suggest that it was taking care of its young. These are some examples of things we have learned from fossils.
How can you distinguish fossils from other rocks?
Fossils are technically rocks, but there are ways to tell if the rock is a fossil. If the rock you find is embedded in another rock, examine it carefully. If it is in sedimentary rock (sandstone, limestone, etc.) it could be a fossil. If it is in igneous or metamorphic rock, it is definitely not a fossil. This is because igneous rocks are formed from cooling lava and any dead organisms buried by the lava would burn up. Metamorphic rocks are made when rocks are put under large amounts of heat and pressure until they are bent and folded and crushed. Fossils or dead organisms would not survive that either.
Shape and texture can help tell if a rock is a fossil. If it looks like a part of a plant or animal, then likely it is a fossil. Some rocks are obviously fossils. With bones, if it is not an entire bone, look inside where the break is. Fossilized bones are often porous inside. Porous means that it has lots of bubbles of air surrounded by bone, kind of like an aero bar.
Fossil Sites in BC
There are many places in BC where fossils have been found such as:
The Burgess Shale – Ancient invertebrate sea life fossils
(located near the border between BC and Alberta)
(located near the border between BC and Alberta)
Tumbler Ridge – Dinosaurs and plant fossils (north-east of Prince George)
The McAbee fossil beds – Plant and animal fossils from about 10 million years after the dinosaurs (located in the interior of the province)
Driftwood Canyon – Ancient fish and insect fossils (near the centre of BC)
Nick Ward says “I have been interested in fossils my whole life. I was very interested in dinosaurs as a young kid, and started learning about fossils. I went to the Royal Tyrell Museum in 2005. Over the years I have collected a large amount of fossils and I remain interested in them.”