Daily Review #1 What happens in radioactive decay? Define half-life. The element chaparralium has a half-life of 24,000 years. If a fossil contains 25% of the original amount of chaparralium, how old is this fossil? Explain how you arrived at this answer. What do you think happened to create the rock in this picture?

Relative vs. Absolute Dating Definition Example Relative Order of events X is older/younger than Y Less specific Three major techniques

Law of Superposition What order were the layers of the cake put down? How are rocks similar? Oldest… Youngest… When layers are horizontal

What if the layers aren’t horizontal?

Principle of Horizontality Rock forms layers horizontally If not horizontal Happened after rock cooled Folding Caused by pressure

Cross-Cutting Occur after rocks form Faults Caused by earthquakes Shift rock layers

Cross-Cutting cont. Intrusions Magma invades cracks Cools into rock

Tell the rock’s story…

Mapping Interior No drilling past crust Seismographs Earthquakes Wave speed effected by density and thickness Study times to pick up seismic waves

Composition of Earth 3 layers Crust Based on compounds present Density differences Crust Outermost 5-100 km Thinnest layer Types Continental Oceanic

Mantle Middle layer 2900 km thick Never visited Conclusions based on Observations on Earth surface Pushes to surface Oceanic volcanoes

Core Center Radius of 3430 km Mostly Fe, some Ni 1/3 of Earth’s mass Very little O, Si, Al, Mg 1/3 of Earth’s mass

Physical Structure Lithosphere Asthenosphere Solid, outer layer Crust Upper mantle Asthenosphere Solid, slow flowing rock Mantle

Outer core Liquid layer Inner core Center Solid, dense

Daily Review #2 Tell the rock’s story… Review quiz – make corrections

Plate Tectonics Plates Divisions of lithosphere Moving on asthenosphere Plate Tectonics

Wegener – Continental Drift Theory Early 1900s Once single landmass - Pangaea Broke up – Laurasia, Gondwana Drifted to present location

Daily Review #3 Put in order of age: Gondwana, Pangaea, South America Sketch the layers of the Earth and label the asthenosphere, lithosphere, outer core, inner core, mantle and crust Fill in the boxes on your layers of the Earth worksheet Composition = if it contains any specific elements (you will not fill this in for all boxes) Thickness = rank from thinnest to thickest

Continental Drift Evidence For Wegener Fitting together of continents Similar things on distant continents Fossils Rocks

How would you explain this evidence?

Sea-Floor Spreading Evidence for continental drift Mid-ocean ridges Tectonic plates moving separating New magma rises Form new oceanic crust Older crust pushed away

Magnetic Reversals Evidence for continental drift Molten rock Magnetic minerals Align with magnetic field Magnetic field reverses 177 times in 85 million years Last 600,000 years ago Recorded in rock Similar pattern to age of rocks

Causes for Plate Tectonics Convection Cools Asthenosphere More dense Heated rock Expands and rises

New material pushed up at ridges Subduction zone Pushes older material away Subduction zone Denser plate sinks Pulls rest of plate