Rocks, Relics, and Soil · Spring Term

Fossil Formation

Exploring how living things become trapped in rock and what these relics tell us about ancient life.

About This Topic

Fossils are the storytellers of the Earth's past. In this topic, Year 3 students explore how living things, plants and animals, become preserved in rock over millions of years. They learn why fossils are almost exclusively found in sedimentary rock and the specific conditions needed for fossilisation, such as rapid burial and the absence of oxygen.

This topic bridges Geography, Science, and History. It meets the KS2 Physical Geography requirements by explaining how the Earth's surface has changed over time. By studying fossils, students can deduce what the environment was like millions of years ago, for example, finding a sea shell fossil on a mountain top tells a powerful story about shifting tectonic plates and changing sea levels.

This topic particularly benefits from hands-on, student-centered approaches where students can act as 'palaeontologists', using evidence to reconstruct past worlds and modeling the layering process that creates these ancient relics.

Learning Objectives

• Classify different types of fossils based on the organism or trace they represent.
• Explain the process of fossilization, detailing the conditions necessary for preservation.
• Analyze fossil evidence to infer past environmental conditions, such as the presence of water or specific climates.
• Compare and contrast the formation of fossils in sedimentary rock versus other rock types.
• Construct a model demonstrating the geological layering that preserves fossils over time.

Before You Start

Types of Rocks

Why: Students need to understand the basic differences between igneous, sedimentary, and metamorphic rocks to grasp why fossils are predominantly found in sedimentary types.

Living Things and Their Habitats

Why: Familiarity with different types of organisms and their environments helps students interpret what fossils reveal about past ecosystems.

Key Vocabulary

Fossil	The preserved remains or traces of ancient living organisms, found in rock.
Sedimentary Rock	Rock formed from accumulated layers of sediment, such as sand, silt, and clay, which often trap and preserve organic material.
Fossilization	The process by which the remains of a dead organism are transformed into a fossil over millions of years, typically involving mineralization.
Paleontologist	A scientist who studies fossils to learn about past life and ancient environments.
Trace Fossil	Evidence of an organism's activity, rather than its actual remains, such as footprints, burrows, or coprolites (fossilized feces).

Active Learning Ideas

Simulation Game: Making a 'Quick' Fossil

Students press plastic dinosaurs or shells into salt dough to create 'mould' fossils. They then fill the mould with plaster of Paris to create a 'cast' fossil. This two-step process helps them understand how the original animal disappears but leaves its shape behind.

⏱ 50 min·Individual

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Inquiry Circle: The Mystery Layer

Provide groups with a 'sedimentary stack' (different coloured sands in a jar) containing hidden 'fossils' (small toys). Students must carefully remove layers from the top down and record what they find, discussing why the 'oldest' fossils are at the bottom.

⏱ 30 min·Small Groups

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Think-Pair-Share: The Shell on the Mountain

Show a photo of a sea shell fossil found at the top of the Himalayas. In pairs, students must come up with a 'geographical theory' for how it got there. Share theories with the class to introduce the idea of tectonic plates lifting the seabed into mountains.

⏱ 20 min·Pairs

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Real-World Connections

Paleontologists working at the Natural History Museum in London analyze dinosaur skeletons and other fossil finds to reconstruct prehistoric ecosystems and understand evolutionary history.

Geologists studying rock formations in the Dorset Jurassic Coast World Heritage Site use ammonite and belemnite fossils to date rock layers and understand ancient marine environments that once covered the area.

Museum curators use fossil displays to educate the public about Earth's history, helping visitors visualize extinct creatures and the environments they inhabited.

Watch Out for These Misconceptions

Common Misconception

Fossils are actually made of bone.

What to Teach Instead

Students often think they are looking at real bones. Explain that a fossil is actually a 'rock copy' of a bone, where minerals have replaced the organic material. Use a 'sponge and sandy water' demonstration to show how minerals can fill tiny holes and turn something hard.

Common Misconception

Everything that dies becomes a fossil.

What to Teach Instead

Actually, fossilisation is very rare! Most things rot or are eaten. Use a 'Fossil Lottery' game where students roll dice to see if their 'animal' was buried quickly enough or if it was eaten, helping them understand the specific conditions needed.

Assessment Ideas

Quick Check

Provide students with images of different fossils (e.g., ammonite, leaf imprint, dinosaur bone, footprint). Ask them to write down the name of the fossil and whether it is a body fossil or a trace fossil, and one thing it tells us about the past.

Exit Ticket

On a slip of paper, ask students to write two key ingredients needed for an organism to become a fossil and one reason why fossils are usually found in sedimentary rock. Collect these as students leave.

Discussion Prompt

Pose the question: 'Imagine you found a fossilized fish in a desert. What does this tell you about the history of that place?' Facilitate a class discussion, guiding students to connect the fossil evidence to past environments and geological changes.

Frequently Asked Questions

Who was Mary Anning?

Mary Anning was a famous British fossil hunter from Lyme Regis. In the early 1800s, she discovered the first complete Ichthyosaur skeleton. She is a great example of how careful observation and fieldwork can lead to massive scientific discoveries, even for people who weren't allowed to go to university at the time.

How can active learning help students understand fossil formation?

Active learning, like creating cast and mould fossils or 'excavating' layers of sand, makes the invisible process of mineralisation and deep time tangible. When students physically see that the 'oldest' layer must be at the bottom, they are learning the law of superposition through experience. It turns a static rock into a dynamic puzzle that they have the skills to solve.

Why don't we find fossils in igneous rock?

Igneous rock is formed from molten magma or lava. If a plant or animal fell into that, it would be burned up instantly! Fossils need the gentle 'settling' of sand or mud in sedimentary rock to be preserved without being destroyed by heat.

What can we learn from fossilised poo?

Fossilised poo is called a 'coprolite'. It's actually very useful for palaeontologists because it tells them exactly what an animal ate! If we find tiny fish scales in a dinosaur's coprolite, we know that dinosaur was a fish-eater.