Fossils: Stories in the rock

Waves crashing on rocks

ALEX JAEGER

The Earth has been populated by living things for billions of years.

Title - 'The Stories in the Rock'

ALEX JAEGER

We know this from the remains of creatures and plants preserved in the rocks. We call these 'fossils'. This is Victoria's Jurassic Coast.

Alex stands on the rocky coastline. Maps appear next to him, illustrating his talk

ALEX JAEGER

The rocks along this coast contain millions of fossils from the age of the dinosaurs. 120 million years ago, Australia and Antarctica were one continent. During this time, this area was a huge prehistoric river valley covered in trees and wetlands.

Alex kneels by a fossil of a tree embedded in the ground

Here you can see a fossilised tree trunk. This tree was alive when dinosaurs walked the Earth. Fossils like these can tell us what happened on Earth in the distant past, so they are very important.

ALEX JAEGER

There are two main types of fossils found along this coast. We can find body fossils, which consist of whole animals, body parts, or pieces of an animal, such as teeth and bones.

Text on screen - 'Fossilised Arthropod'

ALEX JAEGER

We can also find imprints, such as footprints or impressions. These are trace fossils. So how does an animal become a fossil? Usually, an animal rots away when it dies and nothing will be left. But under special circumstances, the animal will be preserved long enough so that a fossil can be formed.

Animated cartoon illustrating Alex's talk

ALEX JAEGER

Imagine a dinosaur died here millions of years ago. It lies down near the river in the soft clay. Fine sediment quickly covers it with a protective layer. The animal will now decompose much more slowly because water and oxygen can no longer get to the body. Over millions of years, more and more layers of sediments are deposited, and the remains are buried deeper and deeper in the earth. The weight of all this sediment creates a lot of pressure, which compacts the animal. Minerals in the rock replace organic tissues, and it literally becomes part of the rock. So how did these fossils end up here along this coast? Over millions of years, Australia separated from Antarctica and moved north. This is called 'continental drift'. The prehistoric valley broke apart and became exposed to the ocean. Erosion made the fossils along this coast visible.

Alex stands by a rock wall

ALEX JAEGER

When you are looking at the rock walls along this coast, you are actually looking back in time. Each layer represents a geological time period in the history of the Earth. Fossils found in the same layer are all roughly the same age. This is referred to as 'relative dating'. Millions of years ago, the Earth was inhabited by extraordinary creatures. We know very little about this time. But what we do know, we know from what is preserved in the rocks. It's up to us to uncover the evidence and read the stories, the stories in the rock. ;Text on screen - 'The Stories in the Rock. A film by Alex Jaeger, yeah 9, 2013, Mornington Secondary College'