Earth Layers Warm-Up #1 What’s inside the earth? If you tried to dig to the center of the Earth, what do you think you would find? Would Earth be solid or hollow? Would it be made of the same material throughout? Respond to the questions using 3-4 sentences, and be sure to justify your thinking.

Layers of the Earth © Copyright 2006.  M. J. Krech. All rights reserved.

(1) basic chemical composition Earth’s layers can be identified using two properties: (1) basic chemical composition (2) state of matter The Earth has layers because as it cooled and formed a planet, the less dense elements of the crust and mantle separated, forming layers around the dense core.

The Four Layers The Earth is composed of four different layers. The crust is the layer that you live on, and it is the most widely studied and understood. The mantle is much hotter and has the ability to flow. The outer core and inner core are even hotter with pressures so great you would be squeezed into a ball smaller than a marble if you were able to go to the center of the Earth!

The Crust The Earth's Crust is like the skin of an apple. It is very thin in comparison to the other three layers. The crust is only about 5-10 kilometers thick under the oceans (oceanic crust) and about 35-70 kilometers thick under the continents (continental crust).

The Crust The crust is a thin solid composed of two rocks. The continental crust is mostly granite. The oceanic crust is basalt. Basalt is much denser than the granite. Because of this the less dense continents ride on the denser oceanic plates.

Think about it… What are the most common elements in the Earth’s crust? What is the difference between the continental crust and oceanic crust?

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

The Lithospheric Plates The crust of the Earth is broken into many pieces called lithospheric plates. These plates "float" on the soft, semi-rigid Asthenosphere.

The Asthenosphere The Asthenosphere is the semi-rigid part of the middle mantle that flows like hot asphalt under a heavy weight. This is considered to be a solid layer with plasticity.

The Mantle The mantle is the largest layer of the Earth at 2900 km thick. The middle mantle is composed of very hot dense rock that flows slowly like asphalt under a heavy weight. The movement of the middle mantle (asthenosphere) is the reason that the crustal plates of the Earth move.

Convection Currents The middle mantle "flows" because of convection currents. Convection currents are caused by the very hot material at the deepest part of the mantle rising, then cooling and sinking again -- repeating this cycle over and over.

The Outer Core The core of the Earth is like a ball of very hot metals and is approximately 2300 km thick. The outer core is so hot that the metals in it are all in a liquid state. The outer core is composed of both melted nickel and iron.

The Inner Core The inner core of the Earth has temperatures and pressures so great that the metals (nickel and iron) are squeezed together and are not able to move about like a liquid, but are forced to vibrate in place like a solid. The inner core is 1200 km thick, and the temperature of the center is estimated at 6,000 degrees Celsius.

Think about it… Take two minutes to reflect on and summarize what you’ve learned so far about the different Earth layers.

How do we know so much about what’s under Earth’s surface? Through INDIRECT EVIDENCE, mostly from seismic waves caused by earthquakes and wells (more on this later this semester...) Sometimes indirect evidence is the only option for scientists to develop a theory.

Click the link below for additional information on each of the Earth’s Layers. http://scign.jpl.nasa.gov/learn/plate1.htm © Copyright 2006.  M. J. Krech. All rights reserved.

Earth Layers Questions Earth Layers Questions *Answer the following questions below in your science journal. Be sure to write each question, and respond using complete sentences.* What two properties are utilized to identify the layers of Earth, and why does Earth have layers? What is the difference between the continental and oceanic crust? Differentiate between the lithosphere and the asthenosphere? How are convection currents created in the mantle? Classify Earth’s layers based on their chemical composition and state of matter. The core of Earth is made out of iron and nickel. The outer core’s temperature is so hot that it melts the metal. The inner core is solid metal. What causes these differences?

Earth Layers Foldable

Answer: 7.6 miles (Only 0.2% of the distance to the earth’s core.) How far have scientists drilled into the earth? Answer: 7.6 miles (Only 0.2% of the distance to the earth’s core.)