Study guide: Rocks, Fossils and Earth History
Use Earth records while distinguishing evidence from inference.
Ideas to explain in your own words
- Igneous rock forms as molten material cools. Sedimentary rock commonly forms from deposited particles or other sediment-forming processes. Metamorphic rock changes under heat and pressure without fully melting.
- A fossil preserves evidence of past life. Its setting can support an inference about a past environment. Not every organism is preserved, and an absence of fossils is incomplete evidence.
- In a simple undisturbed sequence, lower deposited layers are older than layers above. Folding, faults and intrusions can complicate this rule. Our supplied layers explicitly remain undisturbed.
- Several independent clues can strengthen an interpretation. A fossil, sediment texture and layer order answer different questions. A drawn record cannot provide an exact date unless dating evidence is supplied.
Useful vocabulary
- igneous
- formed by cooling molten rock
- fossil
- preserved evidence of past life
- oldest
- bottom layer of this undisturbed sequence
- organism clue
- fossil evidence about past life
Watch your reasoning
- Check what igneous and sedimentary each mean. They describe different clues.
- Check what fossil and past environment each mean. They describe different clues.
- Check what oldest and middle each mean. They describe different clues.
A worked review example
Worked reference-card problem: a card states “formed by cooling molten rock”; a second states “formed from deposited sediment in this case.” The first fits igneous and the second fits sedimentary. The reason is the described function or change, not the order of the cards or a favorite name. If their descriptions exchange places, their category labels exchange too. Keep the supplied descriptions attached to the correct case. Worked reference-card problem: a card states “preserved evidence of past life”; a second states “inferred former setting.” The first fits fossil and the second fits past environment. The reason is the described function or change, not the order of the cards or a favorite name. If their descriptions exchange places, their category labels exchange too. Keep the supplied descriptions attached to the correct case. Worked reference-card problem: a card states “bottom layer of this undisturbed sequence”; a second states “layer between bottom and top.” The first fits oldest and the second fits middle. The reason is the described function or change, not the order of the cards or a favorite name. If their descriptions exchange places, their category labels exchange too. Keep the supplied descriptions attached to the correct case. Worked reference-card problem: a card states “fossil evidence about past life”; a second states “sediment evidence about movement.” The first fits organism clue and the second fits transport clue. The reason is the described function or change, not the order of the cards or a favorite name. If their descriptions exchange places, their category labels exchange too. Keep the supplied descriptions attached to the correct case.
Make a practice plan
- Use an example from Sort rock origins. Say what happens and point to the clue that helps explain it.
- Complete Interpret a fossil observation and correct the specific misconception in its feedback.
- Resolve a changed case from Order undisturbed sediment layers, then combine the four ideas in the transfer task.