Introduction to Earth’s Interior Layers Ms. Bridgeland 6th Grade
3 main interior layers of the Earth • Can anyone name them?
3 main layers of the Earth • 1) The Crust • 2) The Mantle • 3) The Core
The Crust • The layer of rock that forms the Earth’s outer skin • The layer of rock that we stand on • Does it include both dry land and the ocean floor?
The Crust • It does include both dry land and the ocean floor • On the crust, rocks and mountains appear • Also, soil and water cover large parts of the Earth’s surface
The Crust • Size: between 5 and 70 kilometers thick • Where is the Earth’s crust thinnest? • Where is the Earth’s crust thickest?
The Crust’s Size: • Thickest: under high mountains • The mountains are part of the crust • Thinnest: beneath the ocean
The Crust: #1 on your diagram • There are two types of the Earth’s crust. • What are these type types called?
Two types of the Earth’s Crust: • 1) Oceanic Crust: the crust that is beneath the ocean –made of mostly basalt • 2) Continental Crust: the crust that forms the continents –made of mostly granite
The Mantle: #2 on your diagram • The layer of the Earth’s interior that is directly below the Crust (about 40 km from surface) • Size: nearly 3000 kilometers thick • A layer of hot rock that is solid
The Mantle is divided into 3 parts based on what each layer is made of 1) Lithosphere 2) Asthenosphere 3) The Lower Mantle
Lithosphere • The uppermost part of the mantle • About 100 kilometers thick • “Lithos” means “stone” in Greek –solid stone
Asthenosphere • Beneath the lithosphere • Hotter material with higher amounts of pressure • Softer layer that is semi-solid like silly-putty • about 250 km thick
The Lower Mantle • Solid material that extends all the way to the Earth’s core. • Size: 2,650 kilometers
Core • Beneath the mantle • Made of iron and nickel • Consists of two parts
The Core: 2 parts • 1) Liquid Outer Core • 2) Solid Inner Core
The Core: 2 parts • 1) Outer Core: made of liquid (molten metal) • 2) Inner Core: a dense ball of solid metal • *Why is the inner core solid?
In the Inner Core, extreme pressure squeezes the iron and nickel so much that they cannot spread out and become liquid
Outer Core • 3700 degrees Celsius • 30.8% of the Earth’s mass
Inner Core • 1.7% of the Earth’s mass • Thickness: 610 km • Temperature: 6,000 degrees Celsius (about as hot as the surface of the sun)
http://www.youtube.com/watch?v=HOd7PRJMkkQ • Earth’s Interior Layers Rap
How do we know that all of these interior layers exist? Is it possible to dig all the way to the Earth’s core?
Geologists cannot dig to the center of the Earth for several reasons: • 1) Extreme Conditions of the Earth’s interior prevent humans from exploring far below the surface • Temperature is too hot • Pressure is too high • 2) You would have to travel more than 6,000 kilometers to reach the Earth’s center!
How do we know that all of the Earth’s interior layers exist if we cannot travel there?
2 ways that Geologists learn about the Earth’s interior: • 1) Rock samples are blasted to the surface by forces inside Earth such as volcanoes • Can be blasted from depths of more than 100 kilometers • 2) Seismic waves: vibrations that travel through Earth carrying energy released during an Earthquake
What is a Seismic Wave? • http://science.discovery.com/tv-shows/greatest-discoveries/videos/earth-science.htm
1) Why are some of Earth’s layers solid and others liquid? 2) Why doesn’t the Earth melt?3) Why do Earth’s layers change?
The magic answer: HEAT TRANSFER! *3 types of Heat Transfer: What are they?
Heat Transfer: • 1) Radiation • 2) Conduction • 3) Convection
Radiation • The transfer of energy through space • Happens with no direct contact between a heat source and an object • What are examples of radiation?
Examples: • Sunlight is radiation that warms the Earth’s surface • When you feel heat from a fire without touching the flames
Conduction: • Heat transfer between materials that are touching • Example: When you walk barefoot on hot concrete • Example: When a hot pot of water heats up a metal spoon.
Convection • Heat transfer through movement of liquids and gases • When a liquid or gas is heated, the particles expand, or become less dense and rise • When particles cool, they become more dense, and sink back to the bottom • This creates continuous convection cycles
Earth’s Mantle • As the core heats the lower mantle (which is solid), it becomes less dense so rises through the Asthenosphere to the Lithosphere • The Lithosphere is cooling and becoming more dense, so it sinks into the Asthenosphere • This is a continuous process –Convection Cycle • These convection cycles happen over millions of years
Convection Currents are caused by… • Changes in the fluid’s density • The force of gravity –gravity has a higher pull on particles that weigh more
Bill Nye the Science Guy • http://www.youtube.com/watch?v=1B4nRGFHzXs