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Staying Alive - Fossils

Grade 3Cambridge (IGCSE)

Review the key concepts, formulae, and examples before starting your quiz.

🔑Concepts

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The Process of Fossilization:

  1. An animal dies and sinks to the bottom of a water body.
  2. Layers of sediment cover the carcass.
  3. Over millions of years, the sediment turns into rock.
  4. Minerals from the water seep into the bones, a process called permineralization.
  5. The rock is eventually eroded or uplifted, revealing the fossil at the surface.
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Types of Fossils:

  • Body Fossils: Actual remains like bones or teeth.
  • Mold Fossils: A hollow area in sediment in the shape of an organism.
  • Cast Fossils: A solid copy of the shape of an organism, formed when minerals fill a mold.
  • Trace Fossils: Evidence of activities, like footprints.

📐Formulae

Organism+Sediment+Time(≈106 years)→Fossil\text{Organism} + \text{Sediment} + \text{Time} (\approx 10^6 \text{ years}) \rightarrow \text{Fossil}

Hard Parts(CaCO3/Phosphates)=Higher Fossilization Potential\text{Hard Parts} (CaCO_{3} / \text{Phosphates}) = \text{Higher Fossilization Potential}

Depth of Rock Layer∝Age of Fossil\text{Depth of Rock Layer} \propto \text{Age of Fossil}

💡Examples

Problem 1:

A scientist finds two fossils. Fossil A is found 10 meters10 \text{ meters} underground, and Fossil B is found 50 meters50 \text{ meters} underground in the same area of sedimentary rock. Which fossil is likely older?

Solution:

Fossil B is likely older than Fossil A.

Explanation:

According to the Law of Superposition in geology, deeper layers of sedimentary rock were deposited earlier than layers closer to the surface. Therefore, fossils found in deeper layers (50 m50 \text{ m}) are older than those in shallower layers (10 m10 \text{ m}).

Problem 2:

Why is it very rare to find fossils in Igneous rock (rock formed from cooling lava)?

Solution:

The high temperature of magma/lava (T>700∘CT > 700^{\circ}C) destroys organic matter.

Explanation:

Fossils are formed from the remains of living things. Igneous rocks form from molten rock (lava or magma) which is extremely hot. This intense heat would melt or burn any animal or plant remains before they could be preserved.