D O N OW Grab a textbook, turn in progress reports if you have them Why do we have a magnetic field around our planet? What does the lithosphere float on top of? What is the difference between the outter core and the inner core?

O BJECTIVE SWBAT- describe the theory of continental drift and plate tectonics Identify the 7 major plates and the 7 minor plates Identify the three plate boundaries and what feature is associated with each plate boundary

TESTING PLATE TECTONICS Sections 9.4 and 9.5

G UIDED N OTES Your task- Use your textbooks to fill out the first column of the guided notes 233

Earth’s interior consists of three major zones defined by its chemical composition: 1. Crust 2. Mantle 3. Core

1. Thin, rocky outer layer of Earth 2 types: continental and oceanic Continental crust is about 5-47 miles (very thick) Consists of many rock types Oceanic crust is about 4 miles thick (thin) Composed of igneous rocks

1. Solid, rocky shell that extends to a depth of about 1800 miles 2. Divided into Upper Mantle & Lower Mantle 3. Largest layer of the Earth

1. Made mostly of iron-nickel alloy 2. Very hot 3. Inner core Radius of about 760 miles Due to the extreme pressure, the material is solid Outer core Liquid layer is about 1400 miles thick Earth’s magnetic field is generated from the flow of metallic iron

L ITHOSPHERE Crust and upper most part of the mantle Rigid A STHENOSPHERE Beneath lithosphere Soft and flexible

A German scientist and meteorologist, Alfred Wegener, proposed a hypotheses: Pangaea : The continents had once been joined to form a single supercontinent, Pangaea meaning all land

E VIDENCE FOR CONTINENTAL DRIFT  The Continental Puzzle Similar coastlines on opposite sides of the ocean Continents fit together, like a puzzle  Matching Fossils Fossil organisms found on different landmasses  Rock Types and Structures Several mountain belts end at one coastline and reappear on a landmass across the ocean ○ Appalachian Mountains in US, ending off the coast of Newfoundland (Figure 4 on page 251)  Ancient Climates Glacier evidence, Figure 5 on page 252

Wegener could not provide an explanation of exactly what made the continents move Data on earthquake activity and Earth’s magnetic field became available By 1968, these findings led to a new theory, plate tectonics

The upper most mantle and crust, behave as a strong, rigid layer known as the lithosphere Lithosphere is divided into plates, which move and continually change shape and size (move about 5cm per year) 7 major plates (pages , Figure 8) The grinding movements of the plates generate earthquakes, create volcanoes and deform masses of rock into mountains

Convergent Two plates move together Divergent Two plates move apart Transform (fault) Two plates slide past each other

F EATURES A SSOCIATED WITH BOUNDARIES Volcanoes- Subduction zones (convergent boundaries) Mountain ranges – (convergent boundaries) Sea floor spreading – Ocean Ridge (divergent boundaries) Earthquakes – (transform)

V OLCANO

M OUNTAIN RANGE

S EA FLOOR SPREADING

P LATE TECTONICS

TESTING PLATE TECTONICS Paleomagnetism When a rock forms, it becomes magnetized in the direction parallel to Earth’s existing magnetic field Normal polarity – when rocks show the same magnetism as the present magnetic field Reverse polarity – when rocks show the opposite magnetism as the present magnetic field

EVIDENCE FOR PLATE TECTONICS The discovery of strips of alternating polarity, which lie as mirror images across ocean ridges, is among the strongest evidence of seafloor spreading

A NIMATION edu/eoc/teachers/t_tect onics/p_paleomag.htm l

D IAGRAM Draw a diagram and label 1) sea floor spreading happening at a mid ocean ridge 2) Subduction happening between oceaninc and continental crust near a trench 3) A mountain range along a coastline ** Label what type of boundary is associated with each feature (transform, convergent, divergent)

E XIT TICKET

EVIDENCE FOR PLATE TECTONICS Earthquake Patterns Scientists discovered a close link between earthquake origins and ocean trenches Earthquakes occur only within the subducted slab of oceanic lithosphere Ocean Drilling Youngest oceanic crust is at the ridge crest, the oldest crust is at the continental margins Data on the ages of seafloor sediment confirmed the seafloor spreading hypothesis

EVIDENCE FOR PLATE TECTONICS Hot Spot (Volcanic area) A concentration of heat in the mantle produces magma, which rises to Earth’s surface creating volcanic mountains Hot Spot evidence supports the theory that plates move over Earth’s surface Hawaiian Islands

C AUSES OF P LATE M OTION Convection occurring in the mantle, specifically asthenosphere, is the driving force for plate movement Convective flow is the motion of matter resulting from changes in temperature Warm, less dense material rises Cool, more dense material sinks  The unequal distribution of heat within Earth causes convection in the mantle, which drives plate motion

CAUSES OF PLATE MOTION Slab-pull occurs when the cool, dense oceanic crust sinks into the mantle and “pulls” the lithosphere along Ridge-push causes oceanic lithosphere to slide down the sides of the oceanic ridge under the pull of gravity

EARTHQUAKES Earthquakes: The shaking of the earth’s crust caused by the release of energy. A. focus: point within Earth where the EQ begins B. epicenter: location on earth’s surface directly above focus C. faults: 1 cause of EQ’s, large fracture in crust

C AUSES OF E ARTHQUAKES