Layers of the Earth Layers of the Earth The earth is made up of layers (crust, mantle, outer core, and inner core). Each one has a unique make-up to it. Crust This is the outer layer of the Earth about 10 miles or so thick. Mostly made up of rock and loose material. The crust found underneath continents is 3 times thicker than the crust underneath the oceans. Mantle The next layer beneath the crust is called the mantle. It extends to a depth of approximately 1,800 miles and is made of a thick solid rocky substance that represents about 85% of the total weight and mass of the Earth. The first 50 miles of the mantle are believed to consist of very hard rigid rock. The next 150 miles or so is believed to be super-heated solid rock. Below that for the next several hundred miles, the Earth mantle is once again made up of very solid and sturdy rock materials. Outer Core Traveling deeper within the Earth, we next would encounter the Earth’s outer core, which extends to a depth of around 3000 miles beneath the surface. It is believed that this outer core is made up of super-heated liquid molten lava.

This lava is believed to be mostly iron, and nickel. Inner Core Finally, we would reach the Earth’s inner core. The inner core extends another 900 miles inward towards the center of the Earth. It is believed that this inner core is a solid ball of mostly iron, and nickel. The mantle is made of much denser, thicker material, because of this the plates "float" on it like oil floats on water. Many geologists believe that the mantle "flows" because of convection currents. Convection Currents These currents are caused by the very hot material rising, cooling, and sinking over and over again. The next time you heat anything like soup or pudding in a pan you can watch the convection currents move in the liquid. When the convection currents flow in the mantle they also move the crust. The crust gets a free ride with these currents. A conveyor belt in a factory moves boxes like the convection currents in the mantle moves the plates of the Earth. Magma The first question this raises is: what exactly is this "material from the inside"? On our planet, it's magma, fluid molten rock. This material is partially liquid, partially solid and partially gaseous.

Radiation Early Earth The Sun and Earth Form 4.6 Billion Years Ago For the first 9.2 billion years after the Big Bang our Solar System did not exist. The formation of the sun and earth most likely began as the result of a supernova explosion of a nearby dying giant star. As this star began to run out of hydrogen fuel, it expanded into a great red giant and then collapsed on itself and exploded into a major supernova. Most of the giant star's matter would have been ejected into nearby outer space forming a dense cloud, a cosmic nebula. According to the Solar Nebula Model, generally accepted by most cosmologists, stars form in massive, dense nebula clouds mostly made up of dust and hydrogen molecules. a) When a random dense region inside a cloud attracts enough matter, it starts to collapse under its own gravity. It forms a smaller cloud with a distinct center that is more dense than the rest of the cloud. (See a in the chart to the left.) b) As the nebula contracts further, it spins faster and faster eventually flattening into a disk-like object. The center begins to take shape and a ring of material forms revolving around the center.

c) The center of the "proto-star" keeps growing denser and hotter until thermonuclear fusion begins. Hydrogen atoms then begin to combine to form helium atoms, which releases the energy that makes the star begin to shine. Our sun was born and began to shine about 4.6 billion years ago. The remaining material coalesces and swirls around the newborn sun at a faster and faster rate. d) As the dust grains collide, they stick together to build larger objects (this process is called accretion, but it is not the same as black hole accretion). The gravities of these larger objects continue to grow and become strong enough to sweep up more and more of the local surrounding dust and gas molecules. Collisions between the larger items lead to the formation of big chunky objects called "planetesimals". Some planetesimals continue to collide to form planets, including earth which formed about 4.56 billion years ago. Other planetesimals form the solar system moons, asteroids, and comets. (For a more detailed formation explanation, see the Star and Planet Formation on our sister web site).

The early sun did not shine as brightly 4.6 billion years ago (bya) as it does today. The early sun was about 25% to 30% less bright than our current shining star. Without the heat of a bright sun, the earth needed some other mechanisms to ensure that it would not become just another gigantic frozen rock. Enter items such as meteors, volcanoes, and molter iron which made the earth what it is today. These phenomenon will be explained further in the sections below. Top The Very Early Earth 4.5+ Billion Years Ago The very early earth was entirely different than it is now. It was extremely hot, about 1,800°C. The temperatures of a thin hydrogen atmosphere and the surface of the earth were approximately the same. However, there was no molten metallic core like there is today. The core was probably about as warm as the surface and consisted of a magma ocean (liquid rock below the earth's surface) just like the rest of the planet. The surface probably consisted of flowing lava (liquid rock on the earth's surface) with "islands" of solid materials (igneous rock). The crust had not yet formed.

There was no water present and there was very little oxygen in the atmosphere. Although the earth was very hot, the surface was exposed to outer space which was only a few degrees above absolute zero. Therefore the earth was losing heat and cooling all the time, but very slowly in terms of present time frames. By 4.4 bya (billion years ago) scientists believe the earth had cooled below the boiling point of water (100°C) and some water was present. Scientists also believe the early earth was spinning much faster than today. A complete revolution, a day in our terms, was possibly only two to three hours long then, some say six to seven hours. The earliest earthly evidence that has been preserved (at this time) is 4.4 bya. Because there is no proof of anything older, one has to classify information older than 4.4 bya as intelligent conjecture. However, since even the earliest data is so scanty (so few samples), one has to take everything older than 3.9 bya with a grain of salt.

Top The Crust, Mantle And Core Form 4.5 Billion Years Ago As the earth cooled, it is estimated that the first crust formed on its surface roughly a hundred million years after the earth's formation, about 4.46 billion years ago (bya). (Scientific calculations suggest that only a few hundred years would be enough for the earth's entire surface to become solid.) Once the crust had formed, the heat from the interior no longer was exposed to the atmosphere but to the underside of the crust. This allowed the thin atmosphere and surface crust to cool much more quickly. Because of the many large collisions to the early earth, the crust may have been at least partially re-formed several times. On average the crust today consists of about 10 miles of rock and loose materials. At its thickest points the crust is about 50 miles deep. Underneath the continents, the crust is about three times as thick as it is under the oceans. The crust is actually not as solid as it feels to us and it shifts very, very slowly as the continents drift. The different layers of the earth's crust are referred to as plates, and their movements towards and away from each other are called plate tectonics.

The continuous shifting of the earth's plate tectonics causes periodic earthquakes. Under the crust is the mantle that extends to a depth of approximately 1,800 miles. The mantle is made of a thick, solid, rocky substance called peridotite, which is rich in iron and magnesium. The peridotite rock is heavier than surface rock. The mantle makes up about 85% of the total weight and mass of the earth. The average temperature of the mantle is about 2,400°C. The metallic core is an additional 2,200 miles to the center making the total diameter of the earth roughly 4,000 miles. The Metallic Core Forms How the earth came to have the arrangement of four different layers is somewhat of a mystery. Scientists think its beginnings were very messy, the result of many small bodies made up of rock and metals crashing together shortly after the formation of the sun. (Most asteroids are made up of silicate bodies with iron-nickel cores.) One theory is that the planet in its early years was so hot that its rocks and metals melted.

The molten rocks and metals in the "magma ocean" would then have separated into distinct layers as a result of their different densities. Iron and other metals would have drifted downward towards the planet's center, while silicates remained on top. Another theory is that even if the early earth’s temperature was not hot enough to melt the silicates, the molten iron might still have separated out by percolating through the solid silicate layer (like water percolating through coffee grinds. See the illustration at the left.) The idea was that pockets of molten iron (diapirs - from a greek word meaning "to pierce") trapped in the mantle layer would tunnel through the surrounding porous rock to create channels. These channels funneled the molten iron down towards the planet's metallic center core that was slowly forming. It is believed that after about two hundred million years the central core was well formed. As shown in the first illustration above, the metallic core is made up of two parts - an inner core and an outer core. The outer core is about 1,400 miles thick and extends to a depth of about 3200 miles beneath the surface.

The outer core is made up of super heated liquid molten lava. This lava is believed to be mostly iron and nickel and its average temperature is about 4,000°C. Finally, the inner core extends another 800 miles to the center of the earth. It is believed that the inner core is a solid ball of mostly iron and some nickel under a tremendous amount of pressure and at a temperature of about 5,400°C (roughly the same as the surface of the sun). Top The Moon Forms 4.4 Billion Years Ago Scientists believe that shortly after the earth formed about 4.4 billion years ago (bya), it collided with another Mars sized object (meteor or small planet) in an event known as the Giant Impact. It was not a head on collision, but one somewhat off center which changed the earth's axis of rotation by 23 degrees from its natural orientation. The impact shot a cloud of vaporized rock off the earth's surface and into orbit around the earth. Over time, the cloud cooled and condensed into a ring of small, solid bodies, which eventually coalesced to form the moon. The impact probably would have melted all of the surface of the earth.

According to some estimates, the earth would have been as hot as the sun (5,400°C) for about 10,000 years afterwards. If there was water before the Impact, all of it would have evaporated and been blown away. Some scientists believe the moon came into existence after several planet-sized space bodies smashed into the earth one after the other, with the final one actually forming the moon. In the process several impacts repeatedly blew off our planet’s atmosphere and water. To get to the present day neon-to-helium ratio of gases in the atmosphere, the scientists say earth would have had to suffer multiple huge impacts. The earth probably lost its early atmosphere multiple times and its magma surface was partially or totally melted more than once. How do scientists know what happened 4.4 billion years ago? Researchers have samples from volcanoes in Iceland, which have rocks that are among the oldest on earth and retain the signatures of the earth's lower mantle that is closest to the planet's core. From these remnants, they are able to piece together the chemical history of the early earth. Scientists have also found evidence of a magma ocean from several thousand rocks brought back from the moon.

Compare any two samples from early rocks found on earth and those from the moon and you will find the proportions of oxygen and titanium isotopes from the moon are identical to those on earth. However, the isotope proportions found in rock samples from outer space meteorites and those from other planets, like Mars, are quite different. This means that somehow the moon was formed from earthen materials. The Giant Impact theory is the most popular theory among knowledgeable scientists. Top Heavy Bombardment 4.2 to 3.8 Billion Years Ago About 4.2 to 3.8 billion years ago (bya), a period of intense comet and asteroid bombardment is believed to have peppered all the nearby planets including the earth and our moon. Although the earth is still impacted by meteors, it was much, much more intense than we see today. During this period, a very large number of asteroids collided with numerous bodies in our inner solar system, including Mercury, Venus, and Mars. The evidence for these collisions comes primarily from the dating of over 2,000 lunar rock samples brought back by the Apollo astronauts. Many of the samples had clearly remelted after asteroid impacts.

Analysis of the moon rocks showed that the most intense impact period was the Late Heavy Bombardment (LHB), a period of 200 million years from 4.0 to 3.8 bya. The moon's numerous craters are the prime record of past impacts. Unless obliterated by a subsequent larger impact, the craters remain relatively intact because the moon has little atmosphere to weather them. It also has almost no internal activity like the volcanoes, moving tectonic plates, and earthquakes that constantly recirculate the earth's crust and remake our planet's surface. However, while evidence on earth for the early bombardment is scarce because most of it was destroyed by the resultant liquid magma ocean, it is not zero. In 2002 in West Greenland, researchers discovered a version of the element tungsten in sedimentary rocks in amounts normally not found on earth. The tungsten is believed to be of extraterrestrial origin and was estimated to be about 3.8 bya. In 2013, researchers from Denmark also found rocks in Greenland that contained the heavy metals osmium and iridium, which should have disappeared into the earth's core if they were part of the original materials that formed the earth.

These scientists have concluded that they were from meteors that blasted the earth between 4.3 and 4.1 bya. The ultimate cause of the Late Heavy Bombardment remains a mystery, but scientists have come up with several possible explanations for the triggers of the LHB. For example, there might have been a 10th and 11th planet that collided and scattered their remains. It is also possible that the outward migration of Neptune scattered comets and small planetesimals from the asteroid belt. And, the close passage of a neighborhood star could also have initiated widespread scattering of the asteroid belt. The fact is, no one really knows the source of the Late Heavy Bombardment. Top The Early Atmosphere The newly formed earth probably did not have a true atmosphere. Instead, gases which were dissolved in the magma and lava, escaped and probably formed a thin haze above the planet. If a thin atmosphere did exist, it almost certainly was stripped away by the Giant Impact that created the moon. In fact many of the larger impacts that occurred during the early earth would have blasted any accumulated atmospheric gas into space. Therefore, the earth probably did not have a significant atmosphere until the Late Heavy Bombardment period ended.

The main theory explaining the formation of the first atmosphere is a process called volcanic outgassing. As the interior of the earth became very hot, the heat caused some gases to surface into the atmosphere through volcanic emissions. These gases included ammonia, carbon dioxide, carbon monoxide, hydrogen, methane, nitrogen, sulfur dioxide, and water vapor. An additional few minor gases, such as argon, were added by the decay of some radioactive elements within the earth. In particular, note that there probably was only a trace of precious oxygen which makes up about 20% of today's atmosphere. The early earth's atmosphere was much thicker than it is now. Some scientists believe earth's early atmosphere only contained ammonia, helium, hydrogen, and methane, much like the present atmosphere of Jupiter. Others believe it may have contained a large amount of carbon dioxide, as does the atmosphere of Venus. In any case, it was a very harsh and poisonous mixture of gases that any form of life would have had a hard time surviving. Top Oceans Form About 4.2 Billion Years Ago Water currently covers about 71% of the earth's surface. Where did all this water come from?

As the earth cooled below the boiling point of water (100°C) about 4.4 bya, the water vapor the volcanoes had been spewing eventually condensed and formed lakes and maybe even some rivers and small seas. However, scientific calculations indicate there probably was not enough volcano water to form today's huge oceans. There probably was some very early water, but it all would have been vaporized and blown away by the Giant Impact moon event mentioned above. In fact, there probably were quite a few major impacts that followed, each which would have depleted a significant amount of the early earth's water. So where did all our current water come from? The water we have today must have originated after the Giant Impact incident. The leading theory suggests that at some point in the evolution of the Solar System, the outward drift of the orbits of Saturn and Jupiter caused meteor type material from the outer Solar System to be flung inwards into the present day asteroid belt and eventually impacting the earth during the bombardment era. Astronomers realized that there are two obvious sources of water, comets and asteroids, because both contain ice. Either one could easily have delivered enough water to fill the oceans.

Recent analyses of their chemical makeups are tipping the scale toward asteroids. Researchers reported in 2012 that the ratios of hydrogen and nitrogen isotopes in asteroids better match those that we find here on earth. However, the analyses were based on a limited number of samples and so the results are not final. Top Volcanoes Were Everywhere The early earth was covered with many volcanoes. For a long time, most of the volcanoes in the world were underwater. See the under water illustration to the left. Scientists have found that land volcanoes on thick early crusts were pretty much absent during the early planet times. Underwater volcanic eruptions differ in some significant ways from above ground eruptions. The lower temperatures of underwater eruptions mean that the magma cools rather quickly and produces gases like hydrogen sulfide which would have sucked up any available oxygen. The under water volcanically produced early atmosphere was a nasty and noxious blend that would have killed most life. Volcanic eruptions back then are thought to be just like current eruptions. (See the Early Atmosphere above for its gas contents.) The ancient earth should have had oxygen in its early atmosphere but something was converting the oxygen and removing it.

Scientists believe that under water volcanoes effectively scrubbed almost all the oxygen from the atmosphere, binding it into oxygen containing minerals. Above ground volcanoes (see the illustration to the left) release gases that stay hot and do not end up sucking all the oxygen out of the environment. When the large continents began to form much later in the planets life, about 2.5 billion years ago, more volcanoes were above ground than below. Having a mix of volcanoes dominated by land volcanoes allowed oxygen to exist in the atmosphere. Shortly thereafter, the atmospheric oxygen levels began to rise and slowly climbed to our current level of 20%. Very early life did not depend on oxygen. After the earth’s oxygen levels rose, conditions were ripe for the development of complicated life. For more information on the beginnings of life, see the Early Life page. Top The Great Oxygenation Event And The First Ice Age The first ice age is believed to have been around 2.3 billion years ago and is known as the Huronian Ice Age. The catalyst for the first ice age is believed to be a dramatic change in the atmosphere's composition. Previously, the earth’s atmosphere was composed mainly of carbon dioxide and methane, greenhouse gases which kept the atmosphere and the surface quite warm.

However, about 2.4 billion years ago, a rapid rise of oxygen in the atmosphere, known as the Great Oxygenation Event, sucked up most of these greenhouse gases. The Great Oxygenation Event is thought to have been caused by the emergence of plant life on earth, which led to more intake of carbon dioxide and a release of oxygen into the atmosphere. As the amount of carbon dioxide in the atmosphere decreased, the entire planet gradually cooled and sheets of ice began to spread across the surface of the planet. Huronian glacier deposits are laminated sediment deposits composed of alternating layers of silt and clay. These deposits closely resemble the laminated deposits formed within modern glacial lakes at the front of retreating glaciers. These types of deposits are found in many parts of the world, suggesting that Huronian glaciers were widespread during a time where temperatures on earth were consistently much cooler than modern temperatures. Today's temperatures are only able to support year-round glaciation at the polar extremes. In fact, one unlikely area where Huronian deposits are found is on the African continent. The Huronian Ice Age lasted until about 2.1 billion years ago.

Free Flashcards about Layers of the Earth as thin as 5 miles thick underocean The Crust Average thickness about 22 miles The upper crust is made primarily of Sedimentary Rocks These rocks are formed when materials on Earth's surface are worn away or broken up Sedimentary Rocks These rocks are made when magma, molten rock, cools within Earth's surface or near it. These rocks come from volcanoes Igneous These rocks are made when igneous or sedimentary rocks undergo change from heat and pressure.(requires temperature) Metamorphic When 1 type of rock changes to another type of rock The Mantle middle layer when sediments are washed away with the water and harden over many years as the water evaporates. Because these types of rocks require water, often pieces of plants and animals get pressed in the sediments and form fossils 80% of Earth's total volume and 68% of the mass, making it the heaviest part of Earth.

The Mantle The Mantle is believed to be harder due to iron The first 62 miles of this layer of earth is very rigid rock The Mantle The remaining 155 miles of this layer of earth is close to a melting point The Mantle This layer of earth is not a true liquid or solid (Plastic like rock flowing like syrup) The Mantle The Core actually has two sections The Outer Core and the Inner Core The Outer core is believed to be liquid The Outer core is believed to influence the earth's magnetic pull The Inner core is believed to be solid iron and nickel the Earth is how deep 3,958/miles deep This theory of how deep the earth is based on recordings of seismic waves, or shock waves, created by earthquake activity The Crust is made up of solid rocks, soil,and minerals The Crust has temperatures reaching 1,600F — hot enough to melt rocks The Crust ranges in thickness from 5 to 25 miles The Mantle contains a layer of very hot sometimes molten rock The Mantle is about 1,800 miles thick with temps reaching 8,oooF The Mantle is ball shaped and made up mostly of solid iron Inner Core is 4,

000 miles below the surface of the earth Inner Core has temps as high as 13,000F The Outer Core is made up mostly of melted iron The Outer Core has temperatures<reaching up to 11,000F The Outer Core is about 1,400 miles thick The Mantle Scientists call the earth's crust lithosphere (litho means rock or stone) The Earth's lithosphere changes continuously name the 4 main forces that make theses changes to Earth's surface 1.

Changes in the Earth's Crust from tectonic(volcanic/eathquakes) plates 2.Weathering - wearing away of the lithosphere by wind/rain 3. Mass movement- slippage of large areas of rock and soil from landslides 4. Erosion - eating away or slow destruction Alfred Wegener early 1900's came up with the Continental Drift Theory The Continental Drift Theory says 200 million years ago the Earth was one large landmass called PANGAE meaning "all earth" What did Wegener's theory state that the large continents split up and pices drifted apart from each other forming the continents we know today. PANGAEA is divided into 2 parts northern break (Laurasia) southern break (Gondwanaland) In 1960 scientist uncovered evidence of Wegener's theory, what was that evidence? Fossils of a dinosaur were discovered in Africa and South America and it's teeth were discovered in Antarctica. This animal does not swim so the land mass must have been connected. What mountains match up to prove Wegeners theory Cape Mountains of South Africa match up with folded mountains near Bueno Aires, Argentina.

When were the Himalaya Mountains formed when India collided with Asia In the 1950s, scientists were able to study the ocean floor, what did they discover underwater mountains name the longest mountain chain in the world mid ocean ridges Explain why the ocean floor is expanding when exploring the ocean ridge areas, they learned that rocks found near the ridges were younger than those that were further away. This was because magma from deep inside the Earth's mantle was able to rise through vents or cracks to create ridges. As th Plate Tectonic Theory Alfred Wegener's theory of Continental Drift was updated and refined This new version, called Plate Tectonics (blank) explains moving continents, as well as volcanoes, earthquakes and mountains. The Earth's crust, or lithosphere, makes up our plate system (blank) (Pacific, North American, South American, Eurasian, African, Australian, and Antarctic) and several smaller ones All of these plates, with the exception of_______, contain both continental and ocean crust.

The Pacific plate the largest plate that contains almost 20% of the Earth's crust Pacific plate Geologists believe that the plates move about on the asthenosphere because of convection currents, or movements of gases or liquids caused by differences in temperatures, deep within the Earth.

Plate Boundaries The places where the plates meet list the 3 types of plate movement (Plate Boundaries) 1.Divergent Boundaries or SPREADING ZONE: Here, the plates spread away from each other (ocean floor, along the mid-ocean ridges)2.Convergent Boundaries or CONVERGING ZONE: Here, two plates come together - One plate slides over the other plate forcing it d One of the best known transform boundaries San Andreas Fault in California Which Boundary creates the most intense earthquakes Transform Boundaries Beneath the Earth's surface, changes are occurring as well, list 3 types of INTERNAL changes mountain formation, earthquakes, and volcanoes 3 TYPES OF MOUNTAINS The Hawaiian Islands are mountains formed BY Folded mountains are the most common mountains The Alps, Himalayas, Rockies and the Appalachians are examples of folded mountains two lithospheric plates push together over time until these are formed folded mountains Magma is trapped in a pocket beneath the rock layers of the earth and is unable to work its way to the surface. (blank) The Black Hills of South Dakota fault block mountains like the Sierra Nevadas in Utan and Nevada. Geologists believe the Earth's crust bends in as it floats on the fluid-like mantle.

It continues bending until the pressure becomes too great, and then the rocks that form the crust split. fault block mountains earthquake trembling or shaking of the Earth that occurs because of a sudden movement of the crust. more than one million earthquakes each year. What is the most common cause of earthquakes is faulting. Describe Earthquake When the lithospheric plates slide along, the sliding plates break loose,and stored energy is released,The energy travels through the surrounding rocks until the energy is used up. When energy is released through the rocks, it can 1.MOVE THE ROCKS 2. OR V the vibration of rocks during an earthquake seismic waves Activity 9: Earth Layers - Bryce Canyon National Park (U.S. National Park Service) Activity 9: Earth Layers PIT OF THE EARTH Summary: Earth's layers are like a chocolate covered cherry. To introduce the concept of Earth layers, students will diagram and label the candy and describe how each layer of candy relates to an Earth layer.

Instructional Method: To visualize the properties of the different Earth layers Objectives: Students will be able to: List the four main layers of Earth Match the characteristic of each rock layer, with a layer of the cherry Diagram and label the layers of the Earth Time: Chocolate covered cherries, one per student Student page, one per student Plastic knives Paper towels, sponges, etc., for cleanup Vocabulary: Earth is composed of five main divisions or layers: atmosphere, crust, mantle, outer core, and inner core. This lesson will discuss the interactions between the sub-layers and how they affect the crust. The layer we are most familiar with is the crust. Surprisingly, it is the thinnest layer of the four, despite how massive it seems to us. It is approximately 5 to 40 kilometers thick. There are two types of crust: continental crust and oceanic crust. The continental crust is the layer on which we live. The thicker portion of the crust is the continental portion, and likewise, the thinnest part is oceanic crust. The crust is ridged and brittle, but seemingly solid. This layer corresponds with the chocolate cover of the candy.

The continental crust is much lighter, or less dense, than the oceanic crust. Because the oceanic crust is more dense, it submerges below the lighter continental crust when the two collide. (Both types of crust ride on top of the solid lithosphere, which is considered part of the crust. The lithosphere then rides on top of the weaker, partially molten asthenosphere, which is part of the mantle). The mantle is the layer second most familiar to us. The mantle in portions is solid and rocky, but also fluid and molten towards its outer edge in places. Because it is partially solid and partially molten, it can be compared to a plastic, solid but flexible like a Pink Pearl Eraser. It is believed to contain convection currents that drive the movement of crustal plates (refer to Floating Continents). As heat rises to the surface, pieces of crust float around like rafts on a pool, taking thousands of years to move. Mantle thickness ranges from 40 to 2900 kilometers. In our chocolate covered cherry analogy, it is the cream or fluid surrounding the cherry under the chocolate. Below the mantle is the outer core.

Scientists believe that the outer core is composed of a molten, metallic layer 2270 kilometers thick. This layer is believed to contain large amounts of nickel. Scientists have been able to determine that it is a liquid by monitoring earthquake waves as they pass through the Earth's core. The waves dissipate as they pass through this layer in a way that indicates it is liquid and not solid. This is the cherry. If a chocolate covered cherry had a pit, it would be the inner core, a solid iron-rich mass with a radius of 1216 kilometers. At center of the Earth, the pressure from gravity is thought to be so high, that any material in this location would have to be a solid. Scientists believe that the Earth's magnetic fields are related to the orientations of the outer and inner core. The following activity allows students to slice through the layers of Earth discovering the different properties of those layers. Instructional Procedures: Put chocolate covered cherries in the refrigerator and chill them. Do not freeze them. Starting with them cold will help to keep the workspaces cleaner. Make copies of a cross section of Earth layers, one for each student.

Pass out photocopies of Earth layers, plastic knives, paper towels and the cold chocolate covered cherries. Explain to the students that they will get to eat the candy, but to wait until all the materials have been passed out. When all materials are disseminated, have the students spread a paper towel onto their tables and place the candy on the paper towel. Cut the cherry in half, as neatly as you can. (Dissecting a chocolate cherry is very messy business, the chocolate shell might simply break apart. Using knives with a serrated edge and sawing through the shell might prevent the total collapse of the candy's shell). Have them describe the layers of the cherry chocolate on their student pages, labeling each layer and writing one unique characteristic of their choice for each layer. Allow them to eat one half of their candy, but keep the other half on their paper towel. Talk about each layer of Earth as though we are microscopic and standing on the outside edge of the candy. The crust is brittle and is easy to break and is the outer most layer. Under the crust is the mantle; it is flexible and in some places fluid. Next is the outer core, very liquid but dense, just like the cherry.

Describe the concept of the solid metal inner core and ask the students what part of the candy would be like the inner core. (Usually it is removed before the cherry becomes candy: it is the cherry pit). Have them diagram Earth's layers and label each layer correctly. At the bottom of the sheet have them describe each of the Earth's layers using one unique characteristic of their choice and explain in their own words how it correlates with each layer of the chocolate cherry. Finally, have them explain in their own words, how the Earth is NOT like a chocolate covered cherry and how they know this to be true. (The Earth is made out of molten and solid rock, it is too large to be eaten, dirt doesn't taste like chocolate, etc.). Cleanup and eat the other half of the candies. Discussion: If we pretend that we are standing on the surface of this candy, what would we be standing on? How does that chocolate shell correspond with the Earth, and what layer are we standing on? What is below the crust? What do we think it is like? What part of the candy did we say it was like? What about the outer core, where is that found? What about in the cherry candy?

What do we think we know about the inner core? Why did we not see it in the candy today? How is the Earth like this chocolate covered cherry? How is it not like this candy? Why do you think we used this candy to illustrate what we think the inside of the Earth is like? Can we see the inside of the Earth? What part can we see (crust)? What else do we know about the crust? Is it completely solid? Is it broken like some of our chocolates? Variation: This activity can also be done with a hard-boiled egg. The shell is the crust, cracked and broken. The egg white, solid but flexible is the mantle. The yolk can be correlated with the outer core, though it is not fluid, and there is no inner core correlation. This variation is less messy. Included National Parks and other sites: Glossary - Shake, Rattle and Slide - University of Illinois Extension University of Illinois Extension Shake, Rattle and Slide - The Work of Earthquakes, Volcanoes and Glaciers Glossary 1. Accreted terrane - A small piece of the earth’s crust that attaches itself to a larger lithospheric plate. 2.

Aftershock - Smaller earth tremors that happen after an earthquake that can occur several days or weeks after the earthquake. 3. Asthenosphere - Layer of upper mantle that is partially melted, allowing it to be deformed. Asthenosphere is found in the following pages on this website: 06.cfm 07.cfm 11.cfm 17.cfm 4. Caldera - Steep sided depression, caused by explosion and collapse of a volcano. 5. Cinder volcano - Small cone shaped volcano made of mostly ash and rock. Cinder volcano is found in the following pages on this website: 36.cfm 6. Crust - Outermost layer of earth. Crust is found in the following pages on this website: 06.cfm 11.cfm 13.cfm 21.cfm 22.cfm 23.cfm 24.cfm 30.cfm 40.cfm 7. Deposition - Placement of rock and soil from one location to another. Deposition is found in the following pages on this website: 44.cfm 8.

Earthquake - Shaking created in the earth’s crust by land movement. Earthquake is found in the following pages on this website: 15.cfm 29.cfm 30.cfm 31.cfm 32.cfm 9. Epicenter - Point on the earth’s surface directly above where an earthquake occurs. 10. Exosion - Wearing away of rock and soil. 11. Extinction - Complete loss of a species of life. 12. Fault - A fracture of rock caused by movement of the earth’s crust. 13. Firn - Compacted snow granules. 14. Focus - The point in the earth’s crust where movement actually occurs. 15. Geologist - A scientist or person who studies the earth’s surface and rocks and the processes by which they are created, transformed, and broken down. 16. Glacier - Mass of ice and snow flowing slowly downhill under its own weight. 17. Ice Age - A cold period during earth’s geological history. There have been dozens of Ice Ages. Ice Age is found in the following pages on this website: 55.cfm 18.

Igneous - Rock formed from once molten material. 19. Inner core - Deepest layer of earth, believed to be made up of solid iron and nickel. Inner core is found in the following pages on this website: 10.cfm 20. Lava - Molten rock that reaches earth’s surface. Lava is found in the following pages on this website: 26.cfm 35.cfm 37.cfm 38.cfm 41.cfm 21. Lithosphere - Solid portion of earth including the crust and part of the upper mantle. 22. Magma - Molten rock under the earth’s surface. Magma is found in the following pages on this website: 20.cfm 23. Mantle - Layer of earth between the crust and the core. Mantle is found in the following pages on this website: 07.cfm 24. Mantle plume - Also known as a hot spot, an area where magma is close to earth’s surface. 25. Metamorphic - Rock formed from intense heat and pressure. 26.

Modified mercalli intensity scale - The scale for measuring the intensity of an earthquake by observing its effects such as damage to masonry. 27. Moraine - Landform created by deposition of material at edge of a glacier. Moraine is found in the following pages on this website: 50.cfm 72.cfm 28. Outer core - Hot, liquid iron and nickel shell that surrounds the inner core. Outer core is found in the following pages on this website: 09.cfm 29. Pangaea - A supercontinent that existed 225 million years ago and broke apart creating the continents we know today. Pangaea is found in the following pages on this website: 17.cfm 30. Plate - Large pieces of the earth’s crust. Plate is found in the following pages on this website: 14.cfm 15.cfm 19.cfm 20.cfm 23.cfm 24.cfm 25.cfm 27.cfm 30.cfm 39.cfm 40.cfm 31. Plucking - Process where rocks are pulled out of the ground by a glacier. 32.

Richter scale - Measure of earthquake’s strength. 33. Sedimentary - Rock formed from cementation of sediments. Sedimentary is found in the following pages on this website: 64_2.cfm 34. Seismograph - An instrument used by scientists to detect and record vibrations in the ground produced by an earthquake’s shockwaves. 35. Shield volcano - Wide volcano created from eruption of hot, fluid lava. Shield volcano is found in the following pages on this website: 35.cfm 36. Stratovolcano - Tall, steep sided volcano formed from layers of lava, ash, and rock. Stratovolcano is found in the following pages on this website: 37.cfm 37. Subduction - Descent of one crustal plate underneath another plate. 38. Tectonic activity - Crustal movements. 39. Tsunami - A large wave created by land movement underwater. Tsunami is found in the following pages on this website: 33.cfm 40. Volcano - An opening in the earth’s crust from which molten rock, steam, and ash escape.

Question: Which layer of the Earth is believed to be formed of molten iron and nickel?
Answer: Outer core