4/21 & 4/22- 7th Grade Agenda Learning Objective: Discuss how radioactive dating can be used to date the age of rocks. Collect HW: Reading & Notetaking p. 138 – 139 Video: Walking w/ Monsters before Dinosaurs Textbook Reading: p.279-281 HW: Reading & Notetaking p.141 – 142

Reflection Prompt: How can scientists know whether a rock is older than another rock?

What is an index fossil? Index fossils help geologists match rock layer To be useful as an index fossil, a fossil must be widely distributed and represent a type of organism that existed only briefly.

Which fossils are index fossils ? Trilobite Ammonite

These rocks are some of the oldest fossils in the world These rocks are some of the oldest fossils in the world. How old are they? Stromatolites: Remains of ocean reefs created by bacteria more than 3 billion years ago.

What is Radioactive Decay? Radioactive Decay: over time, unstable elements break down or decay by releasing particles and energy.

What is half-life? The half-life of a radioactive element is the time it takes for half of the radioactive atoms to decay.

If Geologic time went by in a single day, when did humans first appear? Humans first appear one second before midnight

Geological Time Scale Paleozoic: Paleo means ancient or early Mesozoic: Meso means middle Cenozoic: Ceno means recent

Reflection Prompt: Write 5 facts that you learned from the video.