“Window” to the Earth’s Interior Formation of the Earth “Window” to the Earth’s Interior

Read: Excerpts from the Bryson article Respond to the prompts

Warm up… Use the pieces you have from your envelope to construct a square. Work by yourself and keep your eyes on your own square!

now… Use the pieces you have from your envelope AND the extra piece I have given you to construct a square. Work by yourself and keep your eyes on your own square!

Which looks like Early Earth during it’s formation? B

How did the Earth form?

?How did Early Earth Form? Homogeneous collection of small solid particles Heat Generated by “friction” causing the interior to become molten Dense material moved to the center; less dense to the edges Materials that hit the Earth caused it to grow As Earth began to COOL Radioactive elements moved out and heat was released

Geologic history began when solid rock formed. over 3.8 billion years ago. No rocks from that time exist today. Why?

Inside the Earth Earth’s layers  Divided 2 different ways: Based on composition Based on physical properties

Modern Earth Three layers based on composition Crust - Outermost layer - solid Mantle - Below crust -liquid Core - Center layer - solid/liquid Layers vary in types of rock, density, temperature, state of matter, and thickness

Read: Excerpts from the Bryson article Respond to the prompts

Composition of the Earth Densest layers are in the core because denser objects always sink due to gravity, while less dense objects float to the surface.

Crust Continental Crust Oceanic Crust Often composed of granite mostly Al, Si, O, Ca, Na, K thick (32 km) Oceanic crust Usually composed of basalt mostly Si, O, Fe, Mg thin (8 km) Why does oceanic crust sit lower than continental crust? - Basalt is more dense than rocks in continental crust.

The Mantle A. Between the core and crust B. Most of the Earth’s mass is in the mantle (thickness = 2900 km or 1800 miles) C. Made of Si, O, Fe & Mg - Contains more Mg, which is denser than Al in the crust D. Temperature = 870oC – 2200oC (1600oF – 4000oF) The top layers of the mantle are hot enough to be plastic or semi-liquid, which allows it to… FLOW (10,000 times slower than the hour hand on a clock!)

There are places in the ocean where the mantle pushes through to form new rock along the ocean floor. As a result, the ocean floor has a similar composition to the mantle.

The Core Makes up 1/3 of the Earth’s mass Made mainly of iron and nickel (the denser elements) Almost no silicon, oxygen, and aluminum

Outer Core Inner Core Solid Fe & Ni Temperature = 5000oC Molten (liquid) Fe & Ni – produces Earth’s magnetic field Surrounds Inner Core Temperature = 2200-5000C Less pressure than inner core Inner Core Solid Fe & Ni Temperature = 5000oC Extreme pressure Why do you think part of the core is liquid, when the inner core is solid? The intense pressure at the center of the Earth squeezes it into a solid!

Discovering Earth’s Layers Oldham 1906 Mohorovičić 1909 Lehmann 1936 Oldham: 1897 Assam 8.1 EQ; 3 distinct waves; change in speed means change in substance-Earth has a core Mohorovicic-seismograms from shallow eq; discontinuity between crust and mantle; some waves were straight but others bent; a transition zone Lehmann-p waves were recorded traveling through core; Lehmann discontinuity-bw the cores-solid inner and liquid outer

Now… Observe the diagram of the Earth Follow the directions and add the layers with regards to physical and structural composition Label according to the directions

Physical Structure of the Earth Five layers based on physical properties: 1) 2) 3) 4) 5) Lithosphere Asthenosphere Mesosphere Outer core Inner core

2 parts: rocky crust and rigid, outermost mantle Litho- = “rock” Lithosphere Asthenosphere  Mesosphere Plastic (flowing) upper mantle directly beneath the lithosphere Astheno- = “weak” Dense, hard lower layers of the mantle Meso- = “middle”

Tectonic Plates

Tectonic Plates Pieces of the lithosphere that move around, floating on top of the denser asthenosphere Each plate fits together with the plates around it. There are 10 or so major plates, but around 50 or more total, including all of the smaller ones.

Oceanic and Continental Crust The South American plate is a single plate containing both continental and oceanic crust. It is surrounded by several other oceanic plates.

Ice Cubes in a Punch Bowl Both oceanic and continental plates float on top of the asthenosphere, like ice cubes floating in water, because of their… Lower density Just like ice cubes, the plates can move around and often bump into each other. Some of the plate sits below the level of the asthenosphere, just like ice displacing water. The thicker continental crust displaces more of the asthenosphere than does oceanic crust.

Mapping the Earth’s Interior During earthquakes, seismic waves (vibrations) are sent in all directions, through the earth. They reach different places at different times because of the ways the waves… BEND and CHANGE SPEED as they pass through the internal layers.

Reflect: How are the five layers divided? 2. Name the five layers and describe a characteristic of each. 3. How do we know the physical state of the layers if we have never traveled to them?

Crust Upper Mantle Lower Mantle Inner Core Outer Core

Reflect: How are the 3 layers divided? Where are less dense materials located? Do the layers follow the laws of density? Do before you leave: Write a mnemonic device or a sentence to remember the composition of each layer?