Science Do Now Silently & Independently, fill in the “What We Already Know” section on the top of the paper on your desk. Take out your “6-4 What is Plate Tectonics” packet from Friday

PLATE TECTONICS March 1, 2016

What we already know 1. Alfred Wegener developed the Theory of Continental drift, which stated that the continents fit together like a puzzle and were once a giant land called Pangea 1. He could not explain how the continents move 1. Through seafloor spreading and the layers of the earth, we are able to explain one way the landscape changes We will learn that the cause of the changing landscape is the theory of plate tectonics

Clarify Misconceptions Most people think that the earth is a solid piece of water with land on top of it. ACTUALLY: earth is made up of pieces that are constantly moving. These pieces do not outline continents or oceans- they are their own shape and size.

What are plate tectonics? Earth’s continental and oceanic crust is divided up into large, solid pieces that float on the lithosphere Remember: the lithosphere is the earth’s crust and upper mantle that is solid rock. The plates float on top of this rock

How do the plates move? Plate Tectonics float on top of the lithosphere, a layer of solid rock Below the lithosphere is the asthenosphere, a layer of rock that flows like a thick liquid in the mantle The moving asthenosphere and convection currents in the mantle cause the lithospheric tectonic plates to move

How do the plates move? Convection Currents! Convection currents are movements of a gas or liquid caused by changes in temperature Convection currents in the mantle are cooler by the crust and hotter by the outer core The cool current sinks and the hot current rises, creating a circular motion The giant convection currents in the Earth’s upper mantle cause the plates to move

How many plates are there? There are 7 large tectonic plates. The largest plate is the Pacific Plate in the Pacific Ocean There are about 14 smaller tectonic plates This makes a total of about 21 tectonic plates We will mostly refer to the 7 larger plates

What is the Theory of Plate Tectonics? The theory of plate tectonics states that the Earth’s crust is broken into pieces (plates) that float on the upper part of the mantle While this is only a theory, we can use seafloor spreading, earthquakes, mountains, and faults to support the theory

Theory of Plate Tectonics definition-quiz.html

Science Do Now Answer the following questions on a piece of paper: What layer of the earth are Plate Tectonics in? What layer do Plate Tectonics float on top of? What type of current drives Plate Tectonics? Open up your workbook to page 102 so I can check your homework.

PLATE BOUNDARIES March 2, 2016

Three main types of plate boundaries Plate Tectonics meet at plate boundaries There are 3 main types of plate boundaries: 1. Convergent Boundaries 2. Divergent Boundaries 3. Transform Boundaries

1. Convergent Boundaries Plates move towards each other Can form: Subduction Zones (oceanic crust slides under continental crust) Volcanoes (due to subduction zone) Mountain Ranges (2 continental crusts collide) Deep Ocean Trench (2 oceanic crusts collide)

Divergent Boundaries Plates move away from each other Can form: Rift Valleys (on land and under water)

Transform Boundaries Plates slide past each other Can Form: Earthquakes

PLATE BOUNDARIES AND FAULT LINES March 8, 2016

Fault Lines & Plate Boundaries Plates meet at plate boundaries Faults form along these boundaries Faults are breaks in earth’s crust where rocks have slipped past each other

Evidence of Faults Rocks have slipped past each other in a variety of capacities, including earthquakes, at subduction zones, rift valleys, and mountain ranges

Hanging Wall The block of rock that sits over the fault Footwall The block of rock that lies under a fault Hanging Wall and Footwall

Three main types of Faults There are 3 main types of faults: 1. Normal 2. Reverse 3. Strike-Slip

1. Normal Faults Occurs when two plates diverge (pull apart) Rock is pulled apart by tension in the earth’s crust The hanging wall slips below the footwall when stress occurs Can form a rift valley

2. Reverse Faults Occurs when two plates compress (push together) The opposite of a normal fault- the footwall slides below the hanging wall Can form mountain ranges

3. Strike Slip Faults Occurs when two plates slide past each other (transform boundary) Broken rock caused the rocks to slip past each other. There is no up or down movement, so there is no hanging wall or footwall Can create earthquakes and the San Andreas fault

Putting it Together: Boundaries and Faults Reverse faults occur at Convergent Boundaries Normal faults occur at Divergent Boundaries Strike-Slip faults occur at Transform Boundaries

Types of Faults Videos Summary of types of faults Animation of types of faults different-types-of-faults

TYPES OF STRESS

Stress Changes the Earth’s Crust Stress is a force that acts on rock to change its shape or volume Stress increases as force increases and adds energy to the rock

3 Types of Stress Stress occurs in the crust Change is the crust is very slow so we cannot directly observe the changing crust There are 3 ways stress changes the shape and volume of rock 1. Tension 2. Compression 3. Shearing

Before Stress Occurs…. Before stress occurs, the continental crust is relatively flat

1. Tension Stress Stress force that pulls on the crust and thins rock in the middle Occurs when two plates diverge (pull apart) along a normal fault

2. Compression Stress Stress force that squeezes rock until it folds or breaks Occurs when two plates converge (come together) along a reverse fault

3. Shearing Stress Stress that pushes a mass of rock in two opposite directions Occurs at a transform boundary when two plates slide past each other along a strike- slip fault

Putting it all together Divergent Boundary Plates move away from each other Reverse Faults occur at convergent boundaries Compression Stress causes the rock to push together until it folds or breaks Can form rift valleys Convergent Boundary Plates move towards each other Normal Faults occur at divergent boundaries Tension Stress pulls the crust so the rock thins in the middle Can form subduction zones, volcanoes, mountain ranges, and deep ocean trenches Transform Boundary Plates slide past each other Strike Slip Faults occur at transform boundaries Shearing Stress pushes the rock in two opposite directions Can Form earthquakes