This packet is everything a parent or guide needs to assess Unit 04 at home — learning targets, the answers that count as correct, the mastery rubric, calibration examples, and a clipboard score sheet. No multiple-choice test: the student shows mastery by ordering a rock sequence, running the half-life simulation, and reasoning from the evidence to an age.
By the end of the Earth History & Geologic Time unit, a student should be able to:
Six criteria, each judged Not yet / Approaching / Mastered (Page 3).
Sequence a rock section and run a decay simulation to read an age.
The student reasons from the evidence to an order and an age (Page 4).
The sequence, the decay data, and the age reasoning kept distinct.
You are making a decision, not adding up points. For each criterion, decide whether the work is Not yet, Approaching, or Mastered — the column language tells you which. A criterion counts as mastered only when the student can both order the evidence and justify the age it points to. A student carries three tokens per term; one token buys a re-do of one criterion on another day, so a single bad afternoon never sinks the unit.
Accept any answer in the synonyms column — they are pre-approved as equivalent. The third column flags the confusions that look close but are not yet, so you can coach precisely.
| Canonical answer | Accepted synonyms | Common confusion / discriminator |
|---|---|---|
| Relative dating | ||
| Superposition | oldest layer on the bottom | In undisturbed layers, the base is the oldest — not the top |
| Cross-cutting | a feature is younger than what it cuts | An intrusion or fault is younger than the rock it cuts through |
| Inclusions | fragments are older than their host | A chunk inside a rock predates the rock around it |
| Unconformity | a gap in the rock record | Missing time — erosion or non-deposition between layers |
| Absolute dating | ||
| Half-life | time for half the parent to decay | Constant for an isotope; not “half the time left” |
| Radiometric dating | dating by isotope decay | Uses the parent-to-daughter ratio; not a guess |
| Parent / daughter isotope | decaying atom / its product | The ratio, plus half-life, gives an absolute age |
| Absolute age | an age in years | A number, vs. relative age (just the order) |
| Fossils & deep time | ||
| Index fossil | widespread, short-lived species | Pins a layer to a narrow time; used to correlate rock |
| Geologic column | standard sequence of rock & time | Eons/eras/periods; the framework for correlation |
| Correlation | matching rock across distant sites | Uses index fossils and layers to line up far-apart rock |
| Deep time | the immense scale of Earth's age | ~4.6 billion years; a million and a billion are not the same |
| Criterion | Not yet | Approaching | Mastered |
|---|---|---|---|
| Relative dating | Cannot order rock layers or thinks the Earth is only a few thousand years old. | Applies superposition to simple layers but stumbles on folds or intrusions. | Uses superposition, cross-cutting, and inclusions to order a disturbed sequence and defend each step. |
| Absolute dating & half-life | Treats radiometric dates as guesses or ignores half-life. | Knows half-life shrinks the parent isotope but cannot compute an age. | Uses parent-to-daughter ratios and half-life to calculate an absolute age and states its assumptions. |
| The geologic column & fossils | Sees fossils and layers as unrelated curiosities. | Names eras or index fossils but cannot use them to correlate rock. | Uses index fossils and the geologic column to correlate and date rock across distant sites. |
| Deep time | Thinks geologic time is intuitive and the Earth is young. | Recites the Earth's age but cannot place events in proportion. | Places major events on a scaled timeline and reasons correctly about durations that dwarf human experience. |
| Lab technique (half-life simulation) | Runs the simulation without tracking decay or connecting it to time. | Collects decay data but misreads the half-life from it. | Runs a half-life simulation, reads the decay curve, and converts a parent-daughter ratio into an age. |
| Integration (cross-domain) | Treats the science as isolated facts; makes no cross-domain connection. | Names a link to history, reading, or writing but cannot defend why it matters. | Connects the unit to its anchor across History · Reading · Writing (plus chosen electives) and defends why the connection matters. |
The split between Approaching and Mastered is reasoning behind the age: not just reciting “billions of years,” but showing how the layers or the decay data get you there. Ask “how do you know it’s older, and by how much?”
Read these before you grade. They show what Mastered and Not yet actually sound like, plus the edge cases where you should coach rather than decide on the spot.
Student: ______________________________________ Date: _______________ Guide: _________________________
| # | Criterion | Decision | Notes |
|---|---|---|---|
| 1 | Relative dating | NY / Appr / Mast | |
| 2 | Absolute dating & half-life | NY / Appr / Mast | |
| 3 | The geologic column & fossils | NY / Appr / Mast | |
| 4 | Deep time | NY / Appr / Mast | |
| 5 | Lab technique (half-life simulation) | NY / Appr / Mast | |
| 6 | Integration (cross-domain) | NY / Appr / Mast |
☐ No ☐ Yes — for criterion: __________ Tokens remaining: ☐ 3 ☐ 2 ☐ 1 ☐ 0
NY = Not yet · Appr = Approaching · Mast = Mastered · Unsure between two levels? Circle the lower one and note what a re-do would need.