Earth's Interior

Earth's Interior

Middle School

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Learning Objectives

• Describe how internal energy from Earth's core drives the cycling of matter.

• Identify Earth's main layers and how geologists study them using seismic waves.

• Explain how convection currents cause melting, crystallization, and deformation.

• Compare the lithosphere, asthenosphere, and the inner and outer core.

Key Vocabulary

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Seismic Waves

These are energy waves from earthquakes that travel through Earth and reveal its internal structure.

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Crust

The crust is the outermost, thin, and solid rock layer of our planet where we live.

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Mantle

The mantle is a hot, thick layer of solid rock found between the Earth's crust and core.

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Core

The core is the extremely hot and dense metallic center of the Earth, composed of iron and nickel.

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Lithosphere

The lithosphere is the rigid outer part of the Earth, which includes the crust and upper mantle.

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Asthenosphere

The asthenosphere is the soft, solid but bendable layer of the upper mantle just below the lithosphere.

Key Vocabulary

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Convection Current

This is the movement within a fluid, like magma, caused by heating and cooling cycles.

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Internal Energy

The heat from Earth's hot interior is a powerful force that drives many geological processes.

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Matter Cycling

This describes the continuous movement and transformation of different materials that make up the Earth.

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Melting

This is the geological process where solid rock heats up and transforms into liquid magma.

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Crystallization

The process by which molten rock, or magma, cools and hardens to form solid crystals.

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Deformation

This is the process by which immense pressure causes rocks to bend, fold, or break.

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How We Study Earth's Interior

Direct Evidence

• Geologists get direct evidence by studying rock samples from deep inside the Earth.

• Deep drilling provides rock samples that give clues about Earth's structure and conditions.

• Volcanoes can bring rocks to the surface from more than 100 kilometers deep.

Indirect Evidence

• Geologists study seismic waves from earthquakes to learn about the planet's interior.

• The speed and path of these waves reveal changes in the Earth's layers.

• P-waves travel through solids and liquids, but S-waves only pass through solids.

Multiple Choice

What are the two primary methods geologists use to study the Earth's interior?

• By using direct evidence from rock samples and indirect evidence from seismic waves.

• By studying ocean currents and atmospheric pressure.

• By analyzing starlight and planetary orbits.

• By measuring surface temperature and wind speed.

Multiple Choice

What is the key difference between how geologists use direct and indirect evidence?

• Direct evidence involves physical rock samples, while indirect evidence involves interpreting seismic waves.

• Direct evidence comes from volcanoes, while indirect evidence comes from deep drilling.

• Direct evidence uses P-waves, while indirect evidence uses S-waves.

• Direct evidence is about Earth's structure, while indirect evidence is about its conditions.

Multiple Choice

If geologists detect P-waves passing through a layer deep inside Earth but do not detect any S-waves, what can they conclude about that layer?

• The layer is liquid, because S-waves cannot travel through liquids.

• The layer must be made of the same material as the surface.

• The layer is a solid, because P-waves were able to pass through it.

• The layer is hollow, because no waves can pass through empty space.

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Earth's Layers: Crust and Mantle

The Crust

• The crust is Earth's thinnest outer layer, including both land and the ocean floor.

• It is a solid rock layer composed mainly of the elements oxygen and silicon.

• Continental crust is like granite, while the denser oceanic crust is similar to basalt.

The Mantle

• Located below the crust, the mantle is a thick layer of hot, solid rock.

• Its top part and the crust form the lithosphere, which sits on the flowing asthenosphere.

• The lower mantle, below the asthenosphere, is hot and rigid due to intense pressure.

Multiple Choice

Which statement correctly identifies Earth's crust?

• It is Earth's thinnest outer layer, composed of solid rock.

• It is a thick layer of flowing hot rock located below the mantle.

• It is the dense, liquid center of the Earth.

• It is a rigid layer formed only by the top part of the mantle.

Multiple Choice

What is the relationship between the crust, the mantle, and the lithosphere?

• The lithosphere is a single rigid layer formed by the crust and the top part of the mantle.

• The lithosphere is another name for the continental crust.

• The lithosphere is a flowing layer that causes the crust to melt.

• The lithosphere is the boundary between the denser oceanic crust and the mantle.

Multiple Choice

Given the structure of Earth's layers, what is the most likely consequence of the asthenosphere's flowing nature?

• The flowing asthenosphere allows the rigid lithosphere to move upon it.

• The intense pressure from the lower mantle causes the lithosphere to become rigid.

• The denser oceanic crust sinks into the asthenosphere, while continental crust floats.

• The heat from the asthenosphere melts the bottom of the lithosphere.

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Earth's Layers: The Core

• The outer core is a hot, liquid layer made mostly of iron and nickel.

• High temperatures keep this layer in a liquid state despite immense pressure.

• The inner core is a dense, solid ball of metal at Earth's center.

• Extreme pressure squeezes the iron and nickel into a solid, despite the heat.

Multiple Choice

What are the inner and outer core primarily made of?

• Iron and nickel

• Rock and magma

• Water and ice

• Gold and silver

Multiple Choice

What is the main reason the inner core is solid while the outer core is liquid?

• The outer core is made of different metals than the inner core.

• The extreme pressure in the inner core forces the metal to be solid.

• The inner core is constantly cooling down from the mantle's influence.

• The outer core is heated by friction from the mantle.

Multiple Choice

Based on the information about Earth's core, what would most likely happen if the pressure on the inner core were significantly reduced while the temperature remained the same?

• It would melt and become a liquid.

• It would become even harder and denser.

• It would cool down significantly.

• It would remain solid due to the high temperature.

Convection and the Mantle

• Hot, less dense rock in the mantle slowly rises toward the top.

• At the top of the mantle, the rock cools and becomes more dense.

• Gravity pulls this cooler, denser rock back down toward the core.

Multiple Choice

What causes hot rock in the mantle to rise?

• It is less dense than the cooler rock around it.

• It is pulled upwards by the Earth's crust.

• It is heavier than the rock at the top of the mantle.

• It is trying to escape the pressure from the core.

Multiple Choice

What causes the cooler rock to sink back towards the core during mantle convection?

• As the rock cools, it becomes more dense, and gravity pulls it down.

• The pressure from the crust pushes the cooled rock back down.

• The rock runs out of heat energy and stops moving completely.

• The rising hot rock forces the cooler rock to move out of the way.

Multiple Choice

What would most likely happen to the convection process if the rock at the top of the mantle did not cool down?

• The rock would stop moving because it would not become dense enough to sink.

• The rock would rise and fall much faster than before.

• The rock would continue to rise indefinitely until it hit the crust.

• The rock's density would increase, but gravity would not affect it.

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Internal Energy and Matter Cycling

• Earth's processes are powered by energy from the sun and its hot interior.

• The energy from deep inside the planet is called its internal energy.

• This internal energy is the driving force behind the cycling of Earth's matter.

• It causes any rock on Earth to be changed into a new type.

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Multiple Choice

What is Earth's internal energy?

• The energy from deep inside the planet.

• The energy that comes from the sun.

• The energy stored in Earth's oceans.

• The energy from the cycling of matter.

Multiple Choice

What is the relationship between Earth's internal energy and the cycling of matter?

• It acts as the driving force for the cycling of Earth's matter.

• It absorbs and stores energy coming from the sun.

• It causes the planet to rotate on its axis.

• It directly heats the surface of the planet.

Multiple Choice

If Earth's internal energy were to significantly decrease, what is the most likely impact on the planet's rocks?

• The process that changes rocks into new types would stop.

• The planet would get more of its energy from the sun.

• The cycling of matter on Earth would speed up.

• The rocks on the surface would remain unchanged forever.

Key Geological Processes

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Melting

• Solid rock transforms into liquid magma or lava when it gets hot.

• This process is driven by the extreme heat from Earth's mantle.

• The molten material created is a key part of the rock cycle.

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Crystallization

• This happens when hot, molten rock begins to cool down significantly.

• Its atoms rearrange into a solid structure, which forms new crystals.

• This is how different types of igneous rocks are originally formed.

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Deformation

• Rocks bend, fold, or break when they are under immense pressure.

• Powerful internal forces of the Earth can reshape entire rock layers.

• This often occurs at the boundaries between the Earth's tectonic plates.

Multiple Choice

What happens during the geological process of melting?

• Liquid magma cools down to form solid crystals.

• Solid rock is transformed into liquid magma or lava.

• Rocks are bent or broken by immense pressure.

• Powerful internal forces reshape rock layers.

Multiple Choice

Which statement describes the process that forms igneous rocks?

• The bending and folding of rock layers under pressure.

• The transformation of solid rock into liquid magma from heat.

• The cooling and solidification of molten rock into crystals.

• The reshaping of rocks at the boundaries of tectonic plates.

Multiple Choice

At the boundary between two of Earth's tectonic plates, immense pressure causes rocks to deform. Based on the information, what other geological process is most likely to be active in this same area?

• The transformation of solid rock into liquid magma due to extreme heat.

• The slow erosion of rock by wind and water.

• The formation of rock from compacted layers of sand.

• The weathering of rock surfaces from exposure to air.

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Common Misconceptions

Misconception	Correction
Earth's mantle is made of liquid magma.	The mantle is mostly solid rock that can flow very slowly.
We have drilled to the mantle.	The deepest holes only go partway through the crust.
Earth's surface is static and unchanging.	Internal energy constantly moves and reshapes the surface.
The inner core must be liquid because it's the hottest layer.	Immense pressure forces the inner core into a solid state.

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Summary

• Geologists study Earth's interior using direct evidence and indirect evidence like seismic waves.

• Earth has three main layers: the crust, mantle, and a two-part core.

• The rigid lithosphere rests on the asthenosphere, moved by mantle convection currents.

• Internal heat drives the cycling of matter, causing melting, crystallization, and deformation.

Poll

On a scale of 1-4, how confident are you about the concepts covered in today's review?

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