This packet is everything a parent or guide needs to assess Unit 08 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 computing an age from a half-life and ordering events by stratigraphic principles.
By the end of the Geologic Time & Earth History unit, a student should be able to:
Six criteria, each judged Not yet / Approaching / Mastered (Page 3).
Model decay across half-lives; compute an age from the ratio.
The student reads Earth history on the geologic time scale (Page 4).
Decay curve, parent/daughter ratio, and age 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 age calculation is defensible and the student can place the events on the geologic time scale. 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 |
|---|---|---|
| Ordering time | ||
| Superposition | law of superposition | In undisturbed layers the oldest is on the bottom |
| Cross-cutting relationships | cross-cutting | A fault or intrusion is younger than the rock it cuts |
| Unconformity | erosional gap | A buried surface — missing time in the record |
| Relative dating | ordering without numbers | Places events in sequence, not in years |
| Dating & the time scale | ||
| Radiometric dating | absolute dating | Puts years on rock using decay of a parent isotope |
| Half-life | decay half-time | Time for half the parent isotope to decay to daughter |
| Geologic time scale | eons / eras / periods | The calendar of Earth history — origin of life to now |
| Deep time | Hutton’s deep time | Earth’s vast age — “no vestige of a beginning, no prospect of an end” |
| Criterion | Not yet | Approaching | Mastered |
|---|---|---|---|
| Relative dating principles | Cannot order rock layers or events. | Names superposition but misapplies cross-cutting or inclusions. | Orders events using superposition, cross-cutting relationships, and inclusions, and reads an unconformity as missing time. |
| Radiometric dating & half-life | Treats absolute age as a guess. | Defines half-life but cannot compute an age. | Computes an age from a parent-to-daughter ratio and a known half-life, and reads a decay curve. |
| The geologic time scale | Cannot place major events in order. | Names eras but not their sequence or defining events. | Places major events — the origin of life, mass extinctions, key evolutionary steps — within their eons, eras, and periods. |
| Deep time & Earth history | Thinks Earth’s past fits human timescales. | Repeats “deep time” but cannot reason at its scale. | Uses Hutton’s deep time to interpret slow processes and mass extinctions across the full sweep of Earth history. |
| Lab technique (radiometric-dating / half-life simulation) | Cannot model decay or read the result. | Runs a half-life simulation but misreads the ratio. | Runs a decay simulation, plots the curve, and converts a parent/daughter ratio into a defensible 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 a defensible number: a student who turns a parent/daughter ratio into years and shows the decay curve has it. Ask “how many half-lives have passed, and how do you know?”
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 principles | NY / Appr / Mast | |
| 2 | Radiometric dating & half-life | NY / Appr / Mast | |
| 3 | The geologic time scale | NY / Appr / Mast | |
| 4 | Deep time & Earth history | NY / Appr / Mast | |
| 5 | Lab technique (radiometric-dating / 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.