Plate Tectonics 2015

The Earth is divided into 4 layers.

CRUST MANTLE INNER CORE OUTER CORE

The Crust Layer of rock that forms Earths outer skin Solid rock included both dry land and ocean floor (rocks, mountains, soils, water) Thin layer (similar to paper thin layer of an onion) Ranges from 5-40 km thick (70km underneath mountains) Composition: oxygen, silicon, aluminum, calcium, iron, sodium, potassium, magnesium Basalt = oceanic crust Granite = continental crust Temperature: whatever is on the surface

Crust The plates move along smoothly but sometimes they get stuck and pressure builds up.

Mantle Rock that is very hot and bendable but solid at the same time. Solid upper mantle and crust = lithosphere (100km thick) Under lithosphere = asthenosphere So hot that it behaves like a plastic material; it flows 2,900 km thick Temperature 870°C Composition: silicon, oxygen, iron, magnesium

Mantle The movement of the mantle create the movement of the Earth’s plates.

Outer Core Inner Core Composition: iron and nickel Temperature: 2200°C State of Matter: thick liquid (molten metal) LOTS of pressure 2,250 km thick Inner Core Composition: iron and nickel Temperature: 5000°C State of Matter: Dense solid metal Extreme pressure (squeezes that atoms of iron and nickel so much they can’t spread out and become liquid) 1,200 km thick

Earth’s Magnetic Field Currents in the liquid outer core force the solid inner core to spin. The inner core spins at a slightly faster rate than the earth’s rotation. Because of this movement, it causes Earth to act like a giant bar magnetic. The magnetic field protects us from the sun’s damaging UV rays.

Earth’s Magnetic Field Earth is a gigantic magnet surrounded by a magnetic field Dipole (bar magnet) Source is the liquid outer core Molten iron in the liquid outer core flows around the solid inner core Unlike bar magnet the Earth’s field changes over time

Convection Currents As liquid heats up, it becomes less dense and rises. When it is away from the heat source, it cools down and becomes more dense and sinks. Heat from the lower mantle and the cores (inner and outer) cause convection currents in the asthenosphere. Heat source Moves up Heats Up Cools Down Moves down

Plate tectonics – theory that states that pieces of the lithosphere are in constant slow motion driven by convection currents in the mantle

Convergent Boundaries Two plates collide The denser plate sinks below the more buoyant plate in a process called subduction. Examples Ocean-Continent: Subduction and Volcanic arc Cascade Mountains (Mt. St. Helens, Mt. Rainier), Andes Mountains Continent-Continent: Mountains Form Himalayan Mts. Ocean-Ocean: Subduction and Volcanic Arc Lesser Antilles

Divergent Boundaries Two plates separating Examples Ocean-Ocean: Seafloor spreading Mid-Atlantic Ridge Continent-Continent: Widening and separating of land Eurasian Plate, African Rift Valley

Transform Boundaries Two plates slide horizontally past one another Examples Continent-Continent: Earthquakes San Andres Fault Ocean-Ocean: Earthquakes East Pacific Rise

Plate Boundaries Foldable

Plate Motion Data Table Page 35 1 2 3 4 5 6 7   Plate Name Latitude within Plate Longitude Revised Latitude (degrees N (+), S (-)) Revised Longitude (degrees E(+), W(-)) Direction (clockwise from N) Speed (mm/yr) Example 20°S 120°E -20 +120  Pacific 20 N 160 W  North American  60 N 60 W  Caribbean  15 N 80 W   Eurasian 40 N Nubia/African Cocos 10 N 110 W South American

Plate Motion Data Table Page 35 1 2 3 4 5 6 7   Plate Name Latitude within Plate Longitude Revised Latitude (degrees N (+), S (-)) Revised Longitude (degrees E(+), W(-)) Direction (clockwise from N) Speed (mm/yr) Example 20°S 120°E -20 +120  Pacific 20 N 160 W +20   -160  North American  60 N 60 W  +60  -60  Caribbean  15 N 80 W   +15  -80  Eurasian 40 N +40 Nubia/African Cocos 10 N 110 W +10 -110 South American -60

Plate Motion Data Table Page 35 1 2 3 4 5 6 7   Plate Name Latitude within Plate Longitude Revised Latitude (degrees N (+), S (-)) Revised Longitude (degrees E(+), W(-)) Direction (clockwise from N) Speed (mm/yr) Example 20°S 120°E -20 +120  Pacific 20 N 160 W +20   -160 -59.73  105.11  North American  60 N 60 W  +60  -60  245.22  25.67  Caribbean  15 N 80 W   +15  -80  252.93  29.68  Eurasian 40 N +40 239.35 20.12 Nubia/African 249.12 16 Cocos 10 N 110 W +10 -110 25.5 16.95 South American -60 257.34 46.76

Which plates do you think will impact North America Which plates do you think will impact North America? Shade it in with your pencil Add the names of those plates to column 1 Choose a location with in each plate where it is easy to read the latitude and longitude. Put a dot on the location Add the latitude and longitude of each location within the plate to the columns 2 and 3 Convert the latitude and longitude of the locations and enter them into columns 4 and 5 Revised Latitude:       If location is °N the number is positive. (20°N = +20) If location is °S the number is negative. (20°S = -20) Revised Longitude:     If location is °E the number is positive. (20°E = +20) If location is °W the number is negative. (20°W = -20) Then go to the plate motion calculator site (http://tectonics.rice.edu/hs3.html Enter the name of the plate and your revised latitude and revised longitude (column 4,5) for the location within that plate. Click on Execute calculation. Enter Speed (Rate) and Direction (Azimuth) into the table. Note: “cw” stands for clockwise.

Seafloor Spreading Notes Read pages 194-200 in the textbook Seafloor Spreading Notes Read pages 194-200 in the textbook. Then answer the following questions and define the words below Page 36 What is seafloor spreading? What evidence is used to support seafloor spreading? mid-ocean ridge seafloor spreading magnetic reversal normal polarity reversed polarity

Seafloor Spreading Notes Read pages 194-200 in the textbook. Then answer the following questions What is seafloor spreading? What evidence is used to support seafloor spreading? mid-ocean ridge - mountain range located on the seafloor in the middle of the ocean seafloor spreading - new oceanic crust forms at a mid-ocean ridge as - old oceanic crust moves away from the ridge magnetic reversal - event in which the magnetic field reverses direction normal polarity - today’s magnetic field; magnets orient themselves to point north reversed polarity - magnetic field in - which magnets orient themselves to point south

Process of Seafloor Spreading At the mid ocean ridge molten material comes up from the mantle, cools, hardens and becomes new crust The new crust spreads out and pushes the old rock to the sides in a continuous process When older oceanic crust reaches a continental crust the more dense oceanic plate is subducted down and forms a trench on the surface. The older crust melts back into the mantle and is recycled by convection currents

Draw and label the diagram representing seafloor spreading and subduction zones Volcanic arc Oldest rock Newest rock Seafloor spreading Basalt Subduction zone Granite Convection currents Oceanic crust Mantle Continental crust Magma Divergent boundary Convergent boundary Mid-ocean ridge Trench

Draw and label the diagram representing seafloor spreading and subduction zones Divergent boundary Seafloor spreading Convergent boundary Subduction zone Mid-ocean ridge Convection currents Basalt Trench Mantle Granite Volcanic arc Oceanic crust Oldest rock Continental crust Newest rock

Draw and label the diagram representing seafloor spreading and subduction zones Divergent boundary Seafloor spreading Convergent boundary Subduction zone Mid-ocean ridge Convection currents Basalt Trench Mantle Granite Volcanic arc Magma Oceanic crust Oldest rock Continental crust Newest rock

On your own piece of paper Boundaries Tour Type of Boundary Location Crust Type Subduction? Volcano? Earthquake? Mountain?

Fault Notes Use the Orange Textbook pages 54-57 page 38-39 Word Definition stress deformation Fault Hanging wall Footwall Word Definition Diagram tension compression shearing Strike-Slip Fault Normal Fault Reverse Fault

Faults Stress – a force that acts on rock to change its shape or volume Strain - a change in the shape of rock caused by stress Compression – squeezing stress Tension – stress that pulls something apart Shear – parallel forces acting in opposite direction Fault - A break in the Earth’s crust where slabs of rock slip past each other

Shearing, tension and compression work over millions of years to change the shape and volume of rock Any change in the volume of Earth’s crust is called deformation. It causes the crust to bend, stretch, break, tilt, fold and slide.

Three Types of Faults Strike-Slip Thrust (Reverse) Normal Form depending on type of plate motion and complex reaction of earth’s lithospheric blocks Strike-slip Normal Thrust Normal

Forms the upper half of the fault Block of rock that forms the lower half of a fault Hanging Wall Footwall

Strike-Slip Fault Shearing creates strike slip faults. Rocks on either side of the fault slip past each other sideways with little up or down motion Before earthquake manure pile was under window where farmer shoveled it out from inside Fault runs right under corner of barn After earthquake manure pile moved over about 10 feet

Normal Faults Tension forces cause these faults. The fault is at an angle so that one block lies above the fault while the other lies below the fault.

Reverse (Thrust) Faults Compression forces. Has the same structure as a normal fault, but the blocks move in the opposite direction.

Mountain Building Over millions of years, fault movement can change a flat plain into a towering mountain range Form by Faulting Folding Anticlines and Synclines Plateaus

Fault-Block Mountains A Mountain that forms where a normal fault up lifts a block of rock. Fault block mountains are distinguished by great sheer rock faces. These form when enormous underground pressure forces a whole rock mass to break away from another. The line at which this break takes place is called a fault.

Folding Mountains Pushing together of part of the earth's crust from the ends, causing it to fold and ripple in the middle. Some great examples of this mountain type are the Appalachians of North America, the Swiss Alps, the Atlas Mountains of Northern Africa, and the Zagros mountains of Iran

Anticline and Syncline Anticline – a fold in rock that bends upward Syncline – a fold in rock that bends downward in the middle to form a bow;

Plateaus Large area of flat land elevated high above sea level. Some form when vertical faults push up a large flat block of rock

Discuss with your partner/neighbor What are the 3 main types of stress in rock? Describe the movements that occur along each of the three types of faults. How does Earth’s surface change as a result of movement along faults? If plate motion compresses part of the crust, what landforms will form there in millions of years?