Plate Tectonics What’s Inside Earth? What’s Inside Earth? (26min)

Earth’s Layers Earth is described by the many different layers that make it up: – Outer Layers: Atmosphere Hydrosphere Biosphere – Inner Layers: Lithosphere Mantle Core

Inner Layers The inner layers of Earth are separated into three different regions: – Lithosphere – Consists of the crust and upper mantle – Mantle - Consists of the asthenosphere and mesosphere – Core - Consists of the outer core and inner core

The Lithosphere The lithosphere is the layer of solid rock that forms Earth’s outer surface; dry land & oceans – Very thin: 5-50km thick 2 Layers: 1.Oceanic Crust Crust beneath the ocean 2.Continental Crust Crust that forms the continents. Lithosphere Oceanic Crust Continental Crust

The Mantle Earth’s largest layer 2 Layers: 1.Asthenosphere Soft and bendable Asthenes = Greek for “weak” 2.Mesosphere Solid rock below the asthenosphere.

The Core 2 parts: 1.Outer Core Liquid – molten metal (iron & nickel) 2.Inner Core Solid metal (iron & nickel) Both Inner and Outer cores make up 1/3 of Earth’s mass but only 15% of its volume.

Earth’s Continents Earth has 7 continents, great landmasses surrounded by water. – Have these landmasses always been in their current location or have they moved throughout history?

Drifting Continents 1910, German scientist Alfred Wegener was curious about the relationship of the continents. – Formed a hypothesis that Earth’s continents have moved. – He began to study: The landforms on Earth The fossils on different continents

Landforms In looking as Earth’s landmasses he noticed that the continents looked like puzzle pieces that could fit together. He believed that the continents had once been joined together in a single landmass and had since drifted apart – Pangaea, “all lands”. Permian – 225myaTriassic – 200mya Jurassic – 150myaCretaceous – 65mya Present Day

Fossils When looking at the locations of fossil remains, Wegener noted that they occurred at locations that would have been connected during Pangaea.

Confirming Wegener’s Theory New technology in the ’s confirmed Wegener’s theory of Continental Drift – the hypothesis that the continents have slowly moved across Earth’s surface. – Sonar bounces sound waves off underwater objects. The time it takes for the echo to arrive back indicates the distance to the object.

Our Ocean Floor With the use of sonar we have been able to map the ocean floor. – Oceans cover ¾ of Earth’s surface and we can’t see the bottom of the oceans. Without sonar we would not know how the bottom of the oceans look. Characteristics of the Ocean Floor: – Mid-Ocean Ridge – Rift Valley – Deep-Ocean Trenches

Mid-Ocean Ridge The mid-ocean ridge is an under water mountain range that extends into all of Earth’s oceans. – Over 50,000km long

Mid-Ocean Ridge A valley runs the length of the mid-ocean ridge, right down its center = Rift Valley. – Twice as deep as the Grand Canyon.

Sea-Floor Spreading The ocean floor moves like a conveyor belt, carrying the continents. – Molten material rises from the mid-ocean ridge, pushing older rock to both sides and creating new ocean floor.

Subduction The ocean floor does not just keep getting wider and wider. Instead it plunges into deep underwater canyons called deep-ocean trenches – Subduction Zones. – The oceanic crust is more dense than the continental crust. When the two meet the oceanic crust sinks back into the mantle. Subduction

Lithospheric Plates Earth’s lithosphere is not a solid outer crust but cracked or broken into several pieces - Plates. The Theory of Plate Tectonics states that pieces of Earth’s lithosphere are in constant, slow motion, driven by convection currents in the mantle. – No plate can budge without affecting the other plates surrounding it; plates collide, pull apart or grind past each other. Links the ideas of continental drift and ocean floor spreading.

Earth’s Lithospheric Plates

Plate Boundaries Plate boundaries are where two plates meet. Depending on the direction the plates are moving you can have three different types of plate boundaries: 1.Transform – sliding past 2.Divergent – moving apart 3.Convergent – moving together

Identifying Plate Boundaries Put the letter of the correct answer in the space provided: A. _____ 1. Transform B. _____ 2. Divergent _____ 3. ConvergentC. C A B

Transform Boundary Plates sliding past one another, in opposite directions – Earthquakes often occur here. Ex. San Andreas in, California

Divergent Boundary Plates moving apart Oceanic spreading centers – Mid-Atlantic ridge Rift Valleys – on land – Great Rift Valley in East Africa.

Convergent Boundary Moving together – The density of the plates determines which one comes out on top: 1. Oceanic vs. Continental Subduction

Convergent Boundary 2. Oceanic vs. Oceanic – Both oceanic crusts sink forming volcanic island arc

Convergent Boundary 3. Continental vs. Continental – Land masses fuse together – Uplift and folding of land – Major mountain ranges Himalayas