1. Structure of the Earth Unit I, Earth Systems and Resources Subtopic I

2. Formation of the Earth The earth formed approximately 4.6 billion years ago The earth formed approximately 4.6 billion years ago(4,600,000,000) We can measure this by looking at the earliest rocks ever formed and using radiometric dating. We can measure this by looking at the earliest rocks ever formed and using radiometric dating. Radiometric dating: Using measurements of radioactive material in an object to determine how old it is Radiometric dating: Using measurements of radioactive material in an object to determine how old it is Mankind has been around for less than 1% of 1% of the earth’s history Mankind has been around for less than 1% of 1% of the earth’s history

4. Formation of the Earth Formed from a cloud of dust and gas that surrounded the sun Formed from a cloud of dust and gas that surrounded the sun As the gas and dust cooled, it formed many large asteroid-like objects As the gas and dust cooled, it formed many large asteroid-like objects These objects collided with each other and combined to form the Earth These objects collided with each other and combined to form the Earth

6. Artists’ conception of the early solar system

7. Asteroid-like objects continued to violently strike the Earth, adding to its size, mass, and heat.

11. Earth remains very hot (melted) inside

13. Crust – Cool – Oceanic and Continental Crust Crust – Cool – Oceanic and Continental Crust Mantle – Hotter – Lower and Upper Mantle Mantle – Hotter – Lower and Upper Mantle Core – Hottest – Inner (solid) and Outer (liquid) Core – Hottest – Inner (solid) and Outer (liquid)

15. Internal Structure of the Earth The Crust Thin, cool outer layer floating on the surface Thin, cool outer layer floating on the surface 0.5% of Earth’s mass 0.5% of Earth’s mass Continental Crust: 20-30 miles thick – rich in Granite Continental Crust: 20-30 miles thick – rich in Granite Oceanic Crust: about 7 miles thick – rich in Basalt Oceanic Crust: about 7 miles thick – rich in Basalt Oceanic Crust is thin, but it is denser than Continental Crust Oceanic Crust is thin, but it is denser than Continental Crust Moho: The boundary between the Crust and Mantle Moho: The boundary between the Crust and Mantle

18. Internal Structure of the Earth The Mantle About 1,800 miles thick and over 1800° Fahrenheit About 1,800 miles thick and over 1800° Fahrenheit Mostly made of Oxygen, Silicon, and Magnesium Mostly made of Oxygen, Silicon, and Magnesium Lower Mantle: Mostly solid, superhot rock Lower Mantle: Mostly solid, superhot rock Upper Mantle: Asthenosphere + part of Lithosphere Upper Mantle: Asthenosphere + part of Lithosphere

20. Lithosphere and Asthenosphere Lithosphere: rigid, cool, rocky layer – includes all Crust (Continental and Oceanic) plus any solid/rocky Upper Mantle Lithosphere: rigid, cool, rocky layer – includes all Crust (Continental and Oceanic) plus any solid/rocky Upper Mantle Asthenosphere: Layer of hot, almost-melted rocks in the Upper Mantle that is capable of flowing Asthenosphere: Layer of hot, almost-melted rocks in the Upper Mantle that is capable of flowing

21. Lithosphere: Rocky layer including Crust and a thin layer of Upper Mantle Lithosphere: Rocky layer including Crust and a thin layer of Upper Mantle Asthenosphere: plastic-like layer under Lithosphere Asthenosphere: plastic-like layer under Lithosphere

23. Internal Structure of the Earth The Core Extremely hot: over 4,000° Fahrenheit Extremely hot: over 4,000° Fahrenheit Inner Core: under such extreme pressure that it remains solid. Mostly made of Iron. Inner Core: under such extreme pressure that it remains solid. Mostly made of Iron. Outer Core: also mostly Iron, but it is liquid. Outer Core: also mostly Iron, but it is liquid.

25. Internal Structure of the Earth

26. Check for Understanding 1) Which layer of Earth’s structure includes the Asthenosphere? 1) Which layer of Earth’s structure includes the Asthenosphere? 2) About how thick is Continental Crust? 2) About how thick is Continental Crust? 3) Which 3 elements make up most of the Mantle? 3) Which 3 elements make up most of the Mantle? 4) Why does the Inner Core remain solid despite being superhot? 4) Why does the Inner Core remain solid despite being superhot? 5) About how old is the earth? How do we know? 5) About how old is the earth? How do we know? 6) Oceanic Crust is rich with: 6) Oceanic Crust is rich with: (a) Granite (b) Silicon (c) Basalt or (d) Plastic