Review of Lessons 1-2

1. Review of Lessons 1-2 • What types of rock are most fossils? How formed? • Six types of fossils • _____________ is change over time. Animals either adapt to the environment over time or they become ___________, or die out. • ______________ are scientists who study fossils. • 2 ways to express the ages of rocks: ___________ age and ____________ age • How can rock layers tell us the age of rocks? • What law is this? • Lava that hardens on the surface of rock layers and forms igneous rock is a ______________. If it pushes into rock below the Earth’s surface, it is an _______. • ___________ fossil: used to match rock layers

2. The Relative Age of Rocks Unconformities and Folding What are the oldest and youngest layers in the last two diagrams? Identify the unconformity. Which is the part of the fold that is overturned?

3. Methods for Dating the Ages of Rocks: Absolute Age • Radioactive decay • Radioactive dating • Half-life • Carbon-14 dating • *The number of years since the rock formed • *Igneous Rock Relative Age • Index Fossils • Extrusion • Intrustion • Law of Superposition • Folding • Uncomformity *The age of rock compared to the age of other rocks *Sedimentary rock

4. Radioactive Decay • Elements in rocks can break down, or decay, over time. Scientists study the amount of decay to discover the age of rocks. • During radioactivedecay, the elements of one atom break down to form atoms of a different element. • This rate (or amount/speed) of decay is measured by the half-life (how long it takes half the atoms to decay).

5. Radioactive Dating Half-Life The half-life of a radioactive element is the amount of time it takes for half of the radioactive atoms to decay. What pattern do you see in the graph?

6. Radioactive Dating • Studying radioactive decay (breakdown of rocks) to determine the age of a rock. • That information helps scientists calculate how old a rock is. • In Carbon-14 dating, scientists see how much of the element carbon-14 is left in a rock. When carbon-14 decays, it turns into Nitrogen-14, so how much carbon-14 is left will tell scientists how long it has been decaying, therefore telling them the age.

7. Radioactive Dating Elements Used in Radioactive Dating

8. Geologic Time – Scientists study the evidence on the Earth and the Moon to determine changes over time. Earth's History in a Day The table shows the times at which some major events would take place. Visualize each event on the clock diagram.

9. Geologic Time The Geologic Time Scale The divisions of the geologic time scale are used to date events in Earth’s history. It helps make it easier to understand how things have changed over time, or _______________.

10. How has Earth Changed over time? • Natural processes such as weathering, erosion and plate tectonics have reshaped Earth’s surface. • The distribution of land and water on Earth has changed over time. • Uniformitarianism – geologic processes that we have today we also had in the past. • This helps scientists understand why and how the Earth changed. The Earth is always changing or evolving. By studying Earth’s changes we see in the present, scientists can make inferences about the past. (like changes in rocks, weather, etc)

11. Geologic Time The Evolving Earth The timeline shows how Earth has changed over time. Pangea The name of the large landmass when the continents were formed into one large landmass.