The Geologic Time Scale
📋 What it is
Scientists divide Earth’s history into eons, eras and periods, each marked by different life and events.
🗣️ Coach says
To organise deep time, geologists split it into named chunks — eons, eras, periods (like the Jurassic or Cretaceous). Each division is defined by the life and big events of that time, and the boundaries often mark major changes, such as mass extinctions. It’s Earth’s official timeline.
🧠 Memory hook
Time scale = eons → eras → periods (Jurassic, Cretaceous…). Boundaries mark big changes/extinctions.
😂 Giggle
What do you call a fossil that's always telling jokes?
A comite — wait, I mean a humerus bone!
😲 Whoa!
The "Jurassic" is named after the Jura Mountains in Europe, where rocks of that age were first studied — many periods are named for where their rocks were found.
✅ Quick check: What usually marks the boundary between two geologic periods?
Say your answer out loud first — then reveal.
A major change in life or a big event — often a mass extinction that reshaped which creatures existed.
Period boundaries reflect major shifts in life/events.
🧪 Try it! (2 minutes)
Order these by time: Triassic, Jurassic, Cretaceous — build a mini timeline of the dinosaur age.