Distribution of Continents Mid-ocean Ridges Trenches. Deformation Metamorphism Volcanism Earthquakes

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1 Earthquakes and Plate Tectonics

2 Global Problems in Geology Distribution of Continents Mid-ocean Ridges Trenches Orogenic Belts Deformation Metamorphism Volcanism Earthquakes

3 Development of Continental Drift Lots of people had noticed that the coastlines of Africa and South America are similar Frank Taylor (1910) Alfred Wegener (1912) Die Entstehung Der Kontinente Und Ozeane

4 Jigsaw-Puzzle Fit of Continental Fit Continents

5 Fit of Continents Across the Atlantic

6 Atlantic 65 m.y. ago

7 Present Day Atlantic

8 Wegener s Theory

9 Theory of Plate Tectonics Plate Tectonics Plate Boundaries Causes of Plate Tectonics

10 What is Plate Tectonics The Earth s crust and upper mantle are broken into sections called plates Plates move around on top of the mantle like rafts

11 The Lithosphere The crust and the upper layer of the mantle together make up a zone of rigid, brittle rock called the Lithosphere.

12 The Asthenosphere The asthenosphere is the semi-rigid part of the middle mantle that flows like hot asphalt under a heavy weight.

13 Plate Tectonics The Earth s crust is divided into 12 major plates which are moved in various directions. This plate motion causes them to collide, pull apart, or scrape against each other. Each type of interaction causes a characteristic set of Earth structures or tectonic features. The word, tectonic, refers to the deformation of the crust as a consequence of plate interaction.

14 The Lithospheric Plates The crust of the Earth is broken into many pieces called plates. The plates "float" on the soft, semirigid asthenosphere.

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16 What is the Lithosphere? The crust and part of the upper mantle = lithosphere 100 km thick Less dense than the material below it so it floats

17 What are tectonic plates made of? Plates are made of rigid lithosphere. The lithosphere is made up of the crust and the upper part of the mantle.

18 What lies beneath the tectonic plates? Below the lithosphere (which makes up the tectonic plates) is the asthenosphere.

19 What is the Asthenoshere? The plastic layer below the lithosphere = asthenosphere The plates of the lithosphere float on the asthenosphere

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21 2 Types of Plates Ocean plates - plates below the oceans Continental plates - plates below the continents

22 Plate Boundaries

23 Three types of plate boundary Divergent Convergent Transform

24 Divergent Boundaries Boundary between two plates that are moving apart or rifting RIFTING causes SEAFLOOR SPREADING

25 Divergent Boundaries Divergent boundaries are also present under continents during the early stages of continental breakup Beneath a continent, magma wells up, and the crust is initially elevated, stretched and thinned

26 Rift Valley The stretching produces fractures and rift valleys. During this stage, magma typically intrudes into the fractures and flows onto the valley floor Example: East African Rift Valley

27 Features of Divergent Boundaries Mid-ocean ridges rift valleys fissure volcanoes

28 Divergent Boundaries Spreading ridges As plates move apart new material is erupted to fill the gap

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32 Convergent Boundaries Boundaries between two plates that are colliding There are 3 types

33 Continent-Continent Boundary Two approaching continents are initially separated by ocean floor that is being subducted under one of them, which, thus, has a volcanic arc When the 2 continents collide Its density is too low, the continental lithosphere cannot subduct although one continent may partly slide under the other

34 Type 1 Ocean plate colliding with a less dense continental plate Subduction Zone: where the less dense plate slides under the more dense plate VOLCANOES occur at subduction zones

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36 Andes Mountains, South America

37 Type 2 Ocean plate colliding with another ocean plate The less dense plate slides under the more dense plate creating a subduction zone called a TRENCH

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39 Aleutian Islands, Alaska

40 Type 3 A continental plate colliding with another continental plate Have Collision Zones: a place where folded and thrust faulted mountains form.

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42 The 6,000-km-plus journey of the India

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44 CARTOON SECTION SHOWING INDIA ASIA COLLISION

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46 Collision Belts Island Arc-Continent Collision Mountain Building Continent-Continent Collision Mountain Building

47 Transform Fault Boundaries Boundary between two plates that are sliding past each other EARTHQUAKES along faults

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49 San Andreas Fault, CA

50 Causes of Plate Tectonics

51 Convection Currents Hot magma in the Earth moves toward the surface, cools, then sinks again. Creates convection currents beneath the plates that cause the plates to move.

52 Plate Movement Plates of lithosphere are moved around by the underlying hot mantle convection cells

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