4/19 & 4/20 - 7th Grade Agenda Learning Objective: Learn about Index Fossils Collect HW: Reading & Notetaking p.135-137 Pass back corrected HW & Test Video: Walking with Monsters before Dinosaurs Text Book Reading: 273 – 277 HW: Reading & Notetaking p. 138 – 139

Reflection Prompt: Describe how Igneous, Sedimentary and Metamorphic rocks are created.

What is relative age of a rock? The relative age of a rock is its age compared to the ages of other rocks

What is the absolute age of a rock? The absolute age of a rock is the number years since the rock was created.

Which layer is the oldest layer of rock? Bottom Layer is the Oldest Layer Law of superposition: In horizontal sedimentary rock layer the oldest layer is at the bottom. Each higher layer is younger than the layers below it.

What is Igneous Intrusion? Igneous Intrusion forms when magma cools and hardens beneath the surface Igneous intrusion is always younger than the rock layer around and beneath it.

Which is older? The fault or the rock layer? A fault is a break in earth’s crust. A fault is always younger than the rock it cuts through.

Why is there gaps in the Geologic Record? Unconformity is a gap in the geologic record.

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.