Notes 11 – Plate Tectonics Earth Science Mrs. Gordon Saturday, October 10, 2015Saturday, October 10, 2015Saturday, October 10, 2015Saturday, October 10, 2015

Review of Earth’s Layers: Crust –Oceanic Crust – ocean floor, made of dense basalt, thinner part of crust –Continental Crust – less dense, mostly granite, thicker Asthenosphere – soft material that can flow like warm plastic Mantle Core –Outer core – liquid rock –Inner core – solid, very dense metal NOTE: the inner and outer core rotate and create Earth’s magnetic fieldNOTE: the inner and outer core rotate and create Earth’s magnetic field

Seafloor spreading review

~ Wegener's evidence + discovery of sea floor spreading led to: A. The Theory of Plate Tectonics - pieces of Earth’s crust are in constant, slow motion driven by convection currents in the mantle.A. The Theory of Plate Tectonics - pieces of Earth’s crust are in constant, slow motion driven by convection currents in the mantle. Every plate affects the other plates around it by colliding together, ripping apart or grinding past each other.Every plate affects the other plates around it by colliding together, ripping apart or grinding past each other.

1. The driving force of Plate Tectonics are CONVECTION CURRENTS. (Heat RADIATES out from the core, warms mantle, material rises, then cools and sinks)1. The driving force of Plate Tectonics are CONVECTION CURRENTS. (Heat RADIATES out from the core, warms mantle, material rises, then cools and sinks) Convection means ‘heat transfer’. When a fluid heats up, the density decreases and it rises, eventually cooling, condensing and sinking again.

B. Where does Earths’ internal heat come from? 1. Radioactive Decay - elements break down into other elements and release heat energy1. Radioactive Decay - elements break down into other elements and release heat energy 2. Residual heat - left over from our planets formation2. Residual heat - left over from our planets formation C. What will happen when Earth’s internal heat runs out? No plate movementNo plate movement No volcanoesNo volcanoes No earthquakesNo earthquakes No mountain buildingNo mountain building

D. PlateD. Plate Boundaries – edges of Earth’s crustal platesthat plates that extend deep into the lithosphere Write these definitions, along with ARROWS showing directions of movement, on the left side page across from these notes – divide page into 4 sections.

1. Convergent1. Convergent Boundaries - Where two plates smash together Boundaries - Where two plates smash together (results in the process of either subduction (trenches and volcanoes) or mountain building (mountains) (results in the process of either subduction (trenches and volcanoes) or mountain building (mountains) –C-C –O-C –O-O Subduction zones – deep trenches where one plate slides under another.Subduction zones – deep trenches where one plate slides under another. The plate will melt as it is pushed deep underground.The plate will melt as it is pushed deep underground.

2. Divergent Boundaries – Where plates are ripping away from each other.2. Divergent Boundaries – Where plates are ripping away from each other. O-O = Results are mid-ocean ridges (new ocean floor is formed here)O-O = Results are mid-ocean ridges (new ocean floor is formed here) C-C = Results are rift-valleysC-C = Results are rift-valleys

3. Transform Boundaries – Where plates slide (grind) past each other in opposite directions. (San Andreas Fault)3. Transform Boundaries – Where plates slide (grind) past each other in opposite directions. (San Andreas Fault)

THE BIG PICTURE

Old / Extra stuff:

How do we know what's inside Earth? Geologists use many different forms of indirect evidence to hypothesize what Earth’s interior is composed of. Ex: Earthquakes, seismic waves, plate movement, drilling Its tough to see first hand b/c as you go deeper underground both temperature and pressure increase. Cool link: Deep DrillingDeep Drilling

1. Theory of Continental Drift – all continents were once connected and called Pangaea, they have since drifted apart. A. Alfred Wegener German scientist,1910

B. Evidence: Landforms, rock layers and fossils match up across the oceans Seafloor spreading Observing forces happening today

A. Sea Floor Spreading 1.PROCESS = ~ Magma is forced upwards towards the crust, between two plates. ~ Magma fills the gap that is created. ~ Magma hardens to form new ocean crust. 2. EVIDENCE = molten material, hydrothermal vents, magnetic stripes, drilling samples