Earths Crust Earths Crust Introduction The Earths crust is the outermost layer of our planet and is less than 1% of the Earth's volume. The crust and the mantle contain different kinds of rocks making them chemically different. The upper mantle rocks are primarily peridotite. The crust contains of a variety of rocks. Igneous rocks, sedimentary rocks, and metamorphic rocks are the main categories of rocks found on the Earth's surface. Continental and oceanic crust, USGS What is the Moho boundary The speed of earthquake waves led to the discovery of the boundary between the Earths crust and the mantle. The Mohorovicic Discontinuity (MOHO) is the boundary between these two layers. Depth of Moho boundary The Moho boundary was named for the Croatian seismologist who discovered it. It is called a discontinuity because the Earths crust varies in depth. The boundary is very shallow beneath oceanic crust and much deeper beneath great mountain ranges like the Himalayas Oceanic crust The oceanic crust is between five and ten kilometers thick. Separating plates form a low pressure area where molten rock collects in magma chambers.

As two oceanic crusts separate basalt flows out onto the ocean floor creating new oceanic crust. Basalt, diabase and gabbro are the primary rocks found in the oceanic crust. These rocks are iron rich, dense and heavier than continental crust rocks. Continental crust When a continental crust and an oceanic crust meet they form a subduction zone. The heavier oceanic crust is forced beneath the lighter continental crust where it subducts into the lithosphere and melts. The oceanic crust is much younger than continental crust that is not destroyed when it collides with another tectonic plate. Continental crust rocks The continental crust contains a wide variety of rocks. Two thousand different minerals have been identified in the crust. Only twenty of these minerals are common. Just ten of the two thousand minerals in the crust combine together in rocks to make up 90% of the crust. Ten silicate minerals Ten minerals that make up 90% of the crust are all silicates because all contain silicon and oxygen. Quartz is pure silicon and oxygen. The rest of the silicate minerals include additional elements in the minerals structure.

Silicate minerals The silicate minerals that make up the continents are lighter than the iron-rich minerals that form in oceanic crust which are derived from the upper mantle. Floating crusts Both the oceanic crust and the continental crust "float" on the asthenosphere that lies beneath the lithosphere. Continental crusts "floats" on the asthenosphere similar to an ice cube floating in water. When they collide with another continental crust they smash together forming great mountain chains instead of being recycled. The continents rise above and sink below the oceanic crust. More Planet Earth Links Earths Interior Our planet is made up of many layers and scientists working as detectives are uncovering its secrets. The Earths Mantle Is the mantle molten rock or solid rock? Find out what we know about this large layer of the Earth. Iceland Volcanoes Did you know volcanoes in Iceland formed because of the Mid Atlantic Ridge and a hot spot? Tectonic Plate Boundaries Find out about the major types of crustal plates and the boundaries around them. Earths Atmosphere Find out which layer meteors burn up, where the International Space station is located and more.

Earths Crust Do you know where the youngest crust on our planet is located and how it forms? Planet Earth Find out about our planet from the Earth's core to the outer reaches of our atmosphere. Kids Fun Science The links on our home page include information about volcanoes, science activities, plate tectonics, the rock cycle and much more. Information about Earth's Layers HOW MANY LICKS DOES IT TAKE TO GET TO THE CENTER? Have you ever wondered how many licks it takes to get to the core of a giant jaw breaker? 1, 2,3 slurp. The earth is in some ways like a giant jaw breaker. It is composed of several layers: the crust, the mantel, and the core. CRUST What comes to mind when you think of the word crust? Perhaps it is the time old saying," Eat your crust!" The earth's crust is a little different then the crust on a piece of bread. It is not soft and chewy, but it hard and composed of different minerals. The thin, outermost layer of the earth is called the crust. It makes up only one percent of the earth's mass. The continental crust is thicker than the oceanic crust.

It can range from 25 km thick at the edges to 70 km thick near the center. The oceanic crust on the other hand is only about 7 km thick and considerably more dense. The crust and the uppermost part of the mantle make up the lithosphere, a solid region that is broken into plates. It is about 65 to 100 km thick. MANTLE The mantle is the layer below the crust. It makes up almost two thirds of the earth's mass and is about 2900 km thick. The mantel is divided into two regions, the upper and lower sections. Directly below the upper section is the asthenosphere. Heat and pressure cause a small amount of melting to occur in the asthenosphere. While still solid, the asthenosphere is able to flow. The ability of a solid to flow is called plasticity. See " What's the matter ?" for an activity to demonstrate plasticity. Since the asthenosphere is more liquid than the rest of the mantle, the broken lithosphere plates are able to "float" on it. When the material in the asthenosphere is heated, it becomes less dense and rises.

While the cooler material is more dense tends to sink. Circulating currents carry the warmer material up and the cooler material down. These circular currents in the asthenosphere are called convection currents. The circulating convection currents cause the plates to move. CORE Below the mantle is the core, the center of the earth. It makes up nearly one third the mass of the earth. The core is also divided into two regions, the inner core and the outer core. From seismic or earthquake waves, scientists believe the outer core is a liquid and the inner core is a solid. The outer core is made of iron and is very dense. Scientists hypothesize that the circulation of the outer core causes the magnetic field around the earth. It is believed to be circulating in the counter-clockwise direction giving us the north pole in its present location. It switches about every million years. A record of this "switching" is recorded in the rocks both on land and in the ocean crust. See " Go west young man! But which way is north? "The inner core is made of solid iron and nickel. Many scientists believe it is kept in the solid state because of the extreme pressure from the other layers.

The Earth's Crust: Everything You Need to Know By Andrew Alden Updated May 07, 2016. The Earth's crust is an extremely thin layer of rock that makes up the outermost solid shell of our planet. In relative terms, it's thickness is like that of the skin of an apple. It amounts to less than half of 1 percent of the planet's total mass but plays a vital role in most of Earth's natural cycles. The crust can be thicker than 80 kilometers in some spots and less than one kilometer thick in others. Underneath it is lies the mantle , a layer of silicate rock approximately 2700 kilometers thick. The mantle accounts for the bulk of the Earth. The crust is composed of many different types of rocks that fall within three main categories: igneous , metamorphic and sedimentary . However, most of those rocks originated as either granite or basalt. The mantle beneath is made of peridotite. Bridgmanite, the most common mineral on Earth , is found in the deep mantle. How We Know the Earth Has a Crust We didn't know the Earth had a crust until the early 1900s.

continue reading below our video Test Your General Science Knowledge Up until then, all we knew was that our planet wobbles in relation to the sky as if it had a large, dense core - astronomical observations told us so. Then along came seismology, which brought us a new type of evidence from below: seismic velocity. Seismic velocity measures the speed at which earthquake waves propagate through the different materials (i.e. rocks) below the surface. With a few important exceptions, seismic velocity within the Earth tends to increase with depth. In 1909, a paper by the seismologist Andrija Mohorovicic established a sudden change in seismic velocity - a discontinuity of some sort - about 50 kilometers deep in the Earth. Seismic waves bounce off it (reflect) and bend (refract) as they go through it, the same way that light behaves at the discontinuity between water and air. That discontinuity, named the Mohorovicic discontinuity or "Moho," is the accepted boundary between the crust and mantle. Crusts and Plates The crust and tectonic plates are not the same thing.

Plates are thicker than the crust and consist of the crust plus the shallow mantle just beneath it. This stiff and brittle two-layered combination is called the lithosphere ("stony layer" in scientific Latin). The lithospheric plates lie on a layer of softer, more plastic mantle rock called the asthenosphere ("weak layer"). The asthenosphere allows the plates to move slowly over it like a raft in thick mud. We know that the Earth's outer layer is made of two grand categories of rocks: basaltic and granitic. Basaltic rocks underlie the seafloors and granitic rocks make up the continents. We know that the seismic velocities of these rock types, as measured in the lab, match those seen in the crust down as far as the Moho. Therefore we're confident that the Moho marks a real change in rock chemistry. The Moho isn't a perfect boundary, because some crustal rocks and mantle rocks can masquerade as the other. However, everyone who talks about the crust, whether in seismological or petrological terms, fortunately means the same thing. In general, then, there are two kinds of crust: oceanic crust (basaltic) and continental crust (granitic).

Oceanic Crust Oceanic crust covers about 60 percent of the Earth's surface. Oceanic crust is thin and young—no more than about 20 km thick and no older than about 180 million years . Everything older has been pulled underneath the continents by subduction . Oceanic crust is born at the mid-ocean ridges, where plates are pulled apart. As that happens, the pressure upon the underlying mantle is released and the peridotite there responds by starting to melt. The fraction that melts becomes basaltic lava, which rises and erupts while the remaining peridotite becomes depleted. The mid-ocean ridges migrate over the Earth like Roombas , extracting this basaltic component from the peridotite of the mantle as they go. This works like a chemical refining process. Basaltic rocks contain more silicon and aluminum than the peridotite left behind, which has more iron and magnesium. Basaltic rocks are also less dense. In terms of minerals, basalt has more feldspar and amphibole, less olivine and pyroxene, than peridotite. In geologist's shorthand, oceanic crust is mafic while oceanic mantle is ultramafic.

Oceanic crust, being so thin, is a very small fraction of the Earth - about 0.1 percent - but its life cycle serves to separate the contents of the upper mantle into a heavy residue and a lighter set of basaltic rocks. It also extracts the so-called incompatible elements, which don't fit into mantle minerals and move into the liquid melt. These in turn move into the continental crust as plate tectonics proceeds. Meanwhile, the oceanic crust reacts with seawater and carries some of it down into the mantle. Continental Crust Continental crust is thick and old - on average about 50 km thick and about 2 billion years old - and it covers about 40 percent of the planet. Whereas almost all of the oceanic crust is underwater, most of the continental crust is exposed to the air. The continents slowly grow over geologic time as oceanic crust and seafloor sediments are pulled beneath them by subduction. The descending basalts have the water and incompatible elements squeezed out of them, and this material rises to trigger more melting in the so-called subduction factory . The continental crust is made of granitic rocks, which have even more silicon and aluminum than the basaltic oceanic crust.

They also have more oxygen thanks to the atmosphere. Granitic rocks are even less dense than basalt. In terms of minerals, granite has even more feldspar and less amphibole than basalt and almost no pyroxene or olivine. It also has abundant quartz . In geologist's shorthand, continental crust is felsic. Continental crust makes up less than 0.4 percent of the Earth, but it represents the product of a double refining process, first at mid-ocean ridges and second at subduction zones. The total amount of continental crust is slowly growing. The incompatible elements that end up in the continents are important because they include the major radioactive elements uranium , thorium and potassium. These create heat, which makes the continental crust act like an electric blanket on top of the mantle. The heat also softens thick places in the crust, like the Tibetan Plateau , and makes them spread sideways. Continental crust is too buoyant to return to the mantle. That's why it is, on average, so old. When continents collide, the crust can thicken to almost 100 km, but that is temporary because it soon spreads out again.

The relatively thin skin of limestones and other sedimentary rocks tend to stay on the continents, or in the ocean, rather than return to the mantle. Even the sand and clay that is washed off into the sea returns to the continents on the conveyor belt of the oceanic crust. Continents are truly permanent, self-sustaining features of the Earth's surface. What the Crust Means The crust is a thin but important zone where dry, hot rock from the deep Earth reacts with the water and oxygen of the surface, making new kinds of minerals and rocks. It's also where plate-tectonic activity mixes and scrambles these new rocks and injects them with chemically active fluids. Finally, the crust is the home of life, which exerts strong effects on rock chemistry and has its own systems of mineral recycling. All of the interesting and valuable variety in geology, from metal ores to thick beds of clay and stone, finds its home in the crust and nowhere else. It should be noted that the Earth isn't the only planetary body with a crust. Venus, Mercury, Mars and the Earth's Moon have one as well . The Layers of the Earth - Planet Earth Planet Earth HELP! Layers of the Earth Uh oh!

I don't know anything about the "Layers of the Earth" and nothing about how many layers there are but luckily my website has as section of Earth Layers. Here are the most main information you should know about the "layers", there are 4 layers in the earth, the crust, the massive mantle, outer core and the solid inner core. The Crust is the thinnest layer in the earth. The Mantle is very massive (huge) if you don't get huge imagine it takes up 80% of the earth now that is huge. The outer core is made of iron and nickel. The inner core is the most inner layer it is very solid. I bet you need more information if you do just scroll down and you'll find non-confusing information. Crust The crust is the most outer layer of the Earth. The crust is very rigid (Hard). The crust is made of granite and basalt. The ocean basically takes up 70% of the crust. The thin rocky crust is made out of silicon, aluminum, calcium, sodium and potassium . The crust is divided into continental plates that drift slowly every year (about a few centimeters).

Just a few kilometers below your feet, its molten rock, extending to for thousands of kilometers down to the planet's super heated iron core. The entire earth's crust occupies just 1% of the earth's volume. The Earth's crust thickness is 30 km thick. The temperature of the crust is 2oo degrees Celsius (392 Fahrenheit) to 400 degrees Celsius (752 Fahrenheit). Mantle The Mantle is the second layer of the earth, it takes up 80% of the Earth. The mantle has two sections (Lithosphere and the Asthenosphere). The temperature of the lithosphere and asthenosphere is 300 to 500 degrees celsius. The mantles temperature 4500 degrees celsius and made of 100% magma. In the mantle, convection currents occur. The convection currents occurs in the lithosphere and the asthenosphere. The mantle is very deep it is 1800- 2900 kilometers deep. A very interesting fact is that the mantle grows about a meter every year. Lithosphere The lithosphere is the upper part of the mantle.

The Lithospheres temperature is about 400 degrees celsius. The lithosphere (lower mantle) is rigid part of the mantle. The lithosphere is not only part of the mantle it is the crust and the upper part of the mantle together. The depth of the lithosphere is 50-100 km thick. Asthenosphere The asthenosphere is the lower part of the mantle. The asthenosphere temperature is 300-500 degrees Celsius. The asthenosphere is ductile and can be pushed and deformed like silly putty in response to the warmth of the Earth. These rocks actually flow, moving in response to the stresses placed upon them by the motions of the deep interior of the Earth. The flowing asthenosphere carries the lithosphere of the Earth, including the continents, on its back. Convection Currents In the mantle are "convection currents" ,which make the mantle move. The lower mantle heats up and rises and cools down then gets pushed down because it is heavier. The currents keeps on going round and round. Convection currents occur because of density of a fluid is related to its temperature. Hot rocks lower in the mantle are less dense than their cooler counterparts below.

The hot rock rises and the cooler rock sinks due to gravity. Outer Core The outer core is the third layer of the earth. The outer core surrounds the inner core . The outer core is the only liquid layer of the Earth. You could say that the outer core is basically a sea of iron and nickel. The outer core is 2100 miles and also is in an range of 200-300 kilometres thick. 7,200 to 9,000 degrees Fahrenheit (4,000 to 5,000 degrees Celsius). Inner Core The inner core is the most inner layer of the earth. The inner core contains iron, the iron in the inner core is not pure (so not just iron) scientists believe it contains sulfur and nickel and also smaller amount of other elements. The inner core is extremely hot it is somewhere between 9000 and 13000 degrees Fahrenheit (5000 and 7000 degrees Celsius).

Create a free website The Earth's Inside The Earth's Inside Thanks to earthquakes, the seimic waves they give off and the instruments used to gather data abouth such events, we now know the chemical composition , temperature, density and depth of the layer's of the Earth's inside. The earth is divided in to four layers: CRUST, MANTLE, OUTER CORE and INNER CORE. CRUST Echo-sounding techniques are used to explore the Earth's crust. Images, similar to sonograms, are produced. A sonogram in the crust is called a seismic reflection. Seiscmic waves from "small explosions or thumper trucks" return echoes from rock layers. Seismographs pick up these echoes.

Some facts about the CRUST: ***two types: oceanic and continental ***calcium (Ca) and sodium (na) aluminium-silicates ***rocky and brittle ***depth of 0-50 kilometers (0-31 miles) ***O0 C Some facts about the MANTLE: ***iron (Fe), magnesium (Mg), aluminium (Al), silicon (Si) and oxygen (O) silicate compunds ***solid but can slowly deform in a plastic manner ***67.3% of Earth's mass ***depth of 10-2890 kilometers(6-1806 miles) ***+10000 C *** convection in this region drives plate tectonics Convection in the MANTLE: Data about P waves and S waves traveling through the mantle has been used to map out convection in the mantle. Waves tell researchers whether the mantle is more or less dense than average, hotter or cooler than average and whether it is rising and falling. The Earth releases internal heat by convecting. Hot mantle rises to the surface and spreads laterally, transporting oceanic and continental plates. Speed of this motion is a few centimeters per year.

The new lithosphere, created at the ocean spreading centers, cools and evetuallu sinks back into the mantle. The subducted crust releases water to form island chains above. Below are two images of mantle convection. Both were created at the Harvard Univerisity Seismology Lab. Red blobs are warmer plumes of less dense material, rising mostly into the ocean-ridge spreading centers. Most of the heat from the Earth's inside emerges at the fast-spreading East Pacific Rise. A huge plume, directly from the Earth's core seems to be spreading there. Blue blobs show where colder, denser material is sinking into the mantle.

OUTER CORE Some facts about the OUTER CORE: ***iron and 10% sulphur (S) and/or oxygen ***molten ***depth of 2890-5150 kilomters (1806-3219 miles) ***37000 C ***convection motion within this region, along with the rotation of the Earth creates an effect that maintains the Earth's magnetic field Convection in the CORE: Some facts about the INNER CORE: ***Iron ***solid and unattached to the mantle ***suspended in molten outer core ***1.7% of the Earth's mass ***depth of 5150-6370 kilometers (3219-3981 miles) In the years since the practice of seismic tomography was first introduced researchers have gathered enough data to provide the world with detailed accurate maps of the layers of the Earth's inside. More recently, scientists have begun to focus more attention on the boundaries between layers, rather that the layers themselves. Many believe that the future of seismic tomography, geophysics and earthquake prediction lies in understanding these boundaries, chemical processes that occur in their vecinity and how such events affect the Earth's surface.

The Earth's Crust, Mantle, and Core - Geology For Kids - By KidsGeo.com How Do We Know? If scientists have never studied any materials from a depth below 7 miles, then how is it that we know what is in the center of the Earth? How can we know what the core of the Earth is made of, if we have never seen it? The answer is actually quite simple. While it is true that we can not study the Earth’s core using visible light, we can study it using other senses. The most important thing we use to sense the Earth’s core are seismic waves. Seismic waves are waves of energy caused either by earthquakes, or by massive manmade explosions. Scientists are able to measure these waves as they pass through the Earth. As these waves encounter different materials, they change in important ways, becoming longer, shorter, faster, or slower. Geologists study these changes in the waves, and are able to draw conclusions about what the core of the Earth must look like. Geologists also can learn a lot about the core of our planet by looking at Earth’s magnetic field. The Magnetic field is created by massive circulations of hot liquid mantle beneath the Earth’s surface.

These clues lead geologists to believe that the Earth is made of four distinct layers. These layers are the crust, the mantle, the outer core, and the inner core. Content on this page requires a newer version of Adobe Flash Player. BBC - GCSE Bitesize: The structure of the Earth Next The Earth consists of four concentric [concentric: Describe shapes (usually circles) which share the same centre point. ] layers: inner core, outer core, mantle [mantle: A zone of hot rock in the interior of the Earth, located between the outer crust and the molten core. ] and crust [crust: The outer layer of the Earth, on top of the mantle. It is between 6 and 48 kilometres thick and includes the continents and the ocean floor. ]. The crust is made up of tectonic plates [tectonic plates: Large areas of the Earth's crust that move slowly on the upper part of the mantle, often colliding and moving away from each other. ], which are in constant motion. Earthquakes and volcanoes are most likely to occur at plate boundaries.

The structure of the Earth The Earth is made up of four distinct layers: The inner core is in the centre and is the hottest part of the Earth. It is solid and made up of iron and nickel with temperatures of up to 5,500°C. With its immense heat energy, the inner core is like the engine room of the Earth. The outer core is the layer surrounding the inner core. It is a liquid layer, also made up of iron and nickel. It is still extremely hot, with temperatures similar to the inner core. The mantle is the widest section of the Earth. It has a thickness of approximately 2,900 km. The mantle is made up of semi-molten rock called magma. In the upper parts of the mantle the rock is hard, but lower down the rock is soft and beginning to melt. The crust is the outer layer of the earth. It is a thin layer between 0-60 km thick. The crust is the solid rock layer upon which we live. There are two different types of crust: continental crust, which carries land, and oceanic crust, which carries water. The diagram below shows the structure of the earth.

In geography, taking a slice through a structure to see inside is called a cross section. Cross section showing structure of the Earth Page: 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 3-5 miles (8 kilometers) thick under the oceans(oceanic crust) and about 25 miles (32 kilometers) thick under the continents (continental crust). The temperatures of the crust vary from air temperature on top to about 1600 degrees Fahrenheit (870 degrees Celcius) in the deepest parts of the crust. You can bake a loaf of bread in your oven at 350 degrees Fahrenheit , at 1600 degrees F. rocks begin to melt. The crust of the Earth is broken into many pieces called plates. The plates "float" on the soft, plastic mantle which is located below the crust. These plates usually move along smoothly but sometimes they stick and build up pressure. The pressure builds and the rock bends until it snaps. When this occurs an Earthquake is the result!

crust - National Geographic Society crust Earth's crust is made of young oceanic material and older, thicker continental material. Map by USGS Silicates, Silicates Everywhere Silicate minerals, mostly feldspars and quartz, are the most abundant minerals in Earth’s rocky crust. Old Crust The oldest rocks yet identified on Earth were discovered in the Jack Hills of Western Australia, part of the Yilgarn Craton, a shield formation. The Jack Hills zircons are about 4.4 billion years old. (The Earth itself is about 4.6 billion years old!) Mining Temperature The TauTona and Mponeng gold mines of South Africa are the deepest in the world, descending about 4 kilometers (2.5 miles) below the surface of the Earth. Although those are deep mines, they are shallow crust. Still, temperatures at the bottom of the mines can climb to 55° Celsius (131° Fahrenheit). A sophisticated air conditioning system lowers the temperature to allow miners to work. “ Crust ” describes the outermost shell of a terrestrial planet .

Our planet ’s thin, 40-kilometer (25-mile) deep crust—just 1% of Earth’s mass—contains all known life in the universe . Earth has three layers: the crust, the mantle, and the core. The crust is made of solid rock s and mineral s. Beneath the crust is the mantle , which is also mostly solid rocks and minerals, but punctuated by malleable areas of semi-solid magma . At the center of the Earth is a hot, dense metal core . Earth’s layers constantly interact with each other, and the crust and upper portion of the mantle are part of a single geologic unit called the lithosphere . The lithosphere’s depth varies, and the Mohorovicic discontinuity (the Moho)—the boundary between the mantle and crust—does not exist at a uniform depth. Isostasy describes the physical, chemical, and mechanical differences between the mantle and crust that allow the crust to “float” on the more malleable mantle. Not all regions of Earth are balanced in isostatic equilibrium. Isostatic equilibrium depends on the density and thickness of the crust, and the dynamic forces at work in the mantle.

Just as the depth of the crust varies, so does its temperature . The upper crust withstands the ambient temperature of the atmosphere or ocean—hot in arid desert s and freezing in ocean trench es. Near the Moho, the temperature of the crust ranges from 200° Celsius (392° Fahrenheit) to 400° Celsius (752° Fahrenheit). Crafting the Crust Billions of years ago, the planetary blob that would become the Earth started out as a hot, viscous ball of rock. The heaviest material, mostly iron and nickel, sank to the center of the new planet and became its core. The molten material that surrounded the core was the early mantle. Over millions of years, the mantle cooled. Water trapped inside minerals erupted with lava, a process called “ outgas sing.” As more water was outgassed, the mantle solidified. Materials that initially stayed in their liquid phase during this process, called “ incompatible element s,” ultimately became Earth’s brittle crust. From mud and clay to diamonds and coal, Earth’s crust is composed of igneous, metamorphic, and sedimentary rocks. The most abundant rocks in the crust are igneous, which are formed by the cooling of magma.

Earth’s crust is rich in igneous rock s such as granite and basalt . Metamorphic rock s have undergone drastic changes due to heat and pressure. Slate and marble are familiar metamorphic rocks. Sedimentary rock s are formed by the accumulation of material at Earth’s surface. Sandstone and shale are sedimentary rocks. Dynamic geologic forces created Earth’s crust, and the crust continues to be shaped by the planet’s movement and energy. Today, tectonic activity is responsible for the formation (and destruction) of crustal materials. Earth’s crust is divided into two types: oceanic crust and continental crust. The transition zone between these two types of crust is sometimes called the Conrad discontinuity . Silicate s (mostly compounds made of silicon and oxygen) are the most abundant rocks and minerals in both oceanic and continental crust. Oceanic Crust Oceanic crust , extending 5-10 kilometers (3-6 kilometers) beneath the ocean floor, is mostly composed of different types of basalts. Geologists often refer to the rocks of the oceanic crust as “sima.” Sima stands for silicate and magnesium, the most abundant minerals in oceanic crust.

(Basalts are a sima rocks.) Oceanic crust is dense, almost 3 grams per cubic centimeter (1.7 ounces per cubic inch). Oceanic crust is constantly formed at mid-ocean ridge s, where tectonic plate s are tearing apart from each other. As magma that wells up from these rifts in Earth’s surface cools, it becomes young oceanic crust. The age and density of oceanic crust increases with distance from mid-ocean ridges. Just as oceanic crust is formed at mid-ocean ridges, it is destroyed in subduction zone s. Subduction is the important geologic process in which a tectonic plate made of dense lithospheric material melts or falls below a plate made of less-dense lithosphere at a convergent plate boundary . At convergent plate boundaries between continental and oceanic lithosphere, the dense oceanic lithosphere (including the crust) always subducts beneath the continental. In the northwestern United States, for example, the oceanic Juan de Fuca plate subducts beneath the continental North American plate. At convergent boundaries between two plates carrying oceanic lithosphere, the denser (usually the larger and deeper ocean basin ) subducts.

In the Japan Trench, the dense Pacific plate subducts beneath the less-dense Okhotsk plate. As the lithosphere subducts, it sinks into the mantle, becoming more plastic and ductile . Through mantle convection , the rich minerals of the mantle may be ultimately “recycled” as they surface as crust-making lava at mid-ocean ridges and volcano es. Largely due to subduction, oceanic crust is much, much younger than continental crust. The oldest existing oceanic crust is in the Ionian Sea, part of the eastern Mediterranean basin. The seafloor of the Ionian Sea is about 270 million years old. (The oldest parts of continental crust, on the other hand, are more than 4 billion years old.) Geologists collect samples of oceanic crust through drilling at the ocean floor, using submersible s, and studying ophiolites. Ophiolite s are sections of oceanic crust that have been forced above sea level through tectonic activity, sometimes emerging as dike s in continental crust. Ophiolites are often more accessible to scientists than oceanic crust at the bottom of the ocean.

Continental Crust Continental crust is mostly composed of different types of granites. Geologists often refer to the rocks of the continental crust as “sial.” Sial stands for silicate and aluminum, the most abundant minerals in continental crust. Sial can be much thicker than sima (as thick as 70 kilometers kilometers (44 miles)), but also slightly less dense (about 2.7 grams per cubic centimeter (1.6 ounces per cubic inch)). As with oceanic crust, continental crust is created by plate tectonics. At convergent plate boundaries, where tectonic plates crash into each other, continental crust is thrust up in the process of orogeny , or mountain-building. For this reason, the thickest parts of continental crust are at the world’s tallest mountain ranges. Like iceberg s, the tall peaks of the Himalayas and the Andes are only part of the region’s continental crust—the crust extends unevenly below the Earth as well as soaring into the atmosphere. Craton s are the oldest and most stable part of the continental lithosphere. These parts of the continental crust are usually found deep in the interior of most continents. Cratons are divided into two categories.

Shield s are cratons in which the ancient basement rock crops out into the atmosphere. Platform s are cratons in which the basement rock is buried beneath overlying sediment . Both shields and platforms provide crucial information to geologists about Earth’s early history and formation. Continental crust is almost always much older than oceanic crust. Because continental crust is rarely destroyed and recycled in the process of subduction, some sections of continental crust are nearly as old as the Earth itself. Extraterrestrial Crust Our solar system’s other terrestrial planets (Mercury, Venus, and Mars) and even our own Moon have crusts. Like Earth, these extraterrestrial crusts are formed mostly by silicate minerals. Unlike Earth, however, the crusts of these celestial bodies are not shaped by the interaction tectonic plates. Despite the Moon’s smaller size, lunar crust is thicker than crust on Earth. Lunar crust is not a uniform thickness and in general tends to be thicker on the “far side,” which always faces away from Earth. Although Mercury, Venus, and Mars are not thought to have tectonic plates, they do have dynamic geology.

Venus, for instance, has at partly- molten mantle, but the Venusian crust lacks enough trapped water to make it as dynamic as Earth’s crust. The crust of Mars, meanwhile, features the tallest mountains in the solar system. These mountains are actually extinct volcano es formed as molten rock erupt ed in the same spot on the Martian surface over millions of years. Eruptions built up enormous mountains of iron-rich igneous rocks that give the Martian crust its characteristic red hue . One of the most volcanic crusts in the solar system is that of Jupiter’s moon Io. The rich sulfide rocks in the Ionian crust paint the moon a dappled collection of yellows, greens, reds, blacks, and whites. Term relatively easy to approach, use, or obtain. accumulation having to do with the surrounding area or environment. arid type of dark volcanic rock. basement rock oldest underlying rock formation in any region. boundary physical, cultural, or psychological feature of an organism, place, or object. Conrad discontinuity seismic boundary between the continental crust and oceanic crust. continental crust thick layer of Earth that sits beneath continents. convergent plate boundary Noun area where two or more tectonic plates bump into each other.

Also called a collision zone. core old, stable part of continental crust, made up of shields and platforms. crucial spotted, or having areas of differently colored shades or tones. dense having parts or molecules that are packed closely together. desert Noun capable of withstanding a certain amount of force by changing form before fracturing or breaking. dynamic always changing or in motion. Earth Noun our planet, the third from the Sun. The Earth is the only place in the known universe that supports life. to explode or suddenly eject material. eventually at some point in the future. extinct volcano volcano that will no longer erupt. extraterrestrial located or formed outside Earth's atmosphere. geologic having to do with the physical formations of the Earth. granite type of hard, igneous rock. granite type of hard, igneous rock. hue tint or general variety of color. iceberg rock formed by the cooling of magma or lava. incompatible element Noun in geochemistry, an element that stays in a liquid phase during the melt or crystallization process. initially chemical element with the symbol Fe. isostasy Noun equilibrium of Earth's crust, where the forces tending to elevate landmasses balance those tending to depress them.

Also called isostatic equilibrium. lava molten rock, or magma, that erupts from volcanoes or fissures in the Earth's surface. lithosphere having to do with Earth's moon or the moons of other planets. magma chemical element with the symbol Mg. malleable flexible and capable of reforming itself without breaking when under stress. mantle mantle convection Noun slow movement of Earth's solid mantle caused by convection currents transferring heat from the interior of the Earth to the surface. metal category of elements that are usually solid and shiny at room temperature. metamorphic rock rock that has transformed its chemical qualities from igneous or sedimentary. mid-ocean ridge inorganic material that has a characteristic chemical composition and specific crystal structure. Mohorovicic discontinuity point between Earth's crust and the mantle below. Also called the Moho. molten solid material turned to liquid by heat. ocean basin depression in the Earth's surface located entirely beneath the ocean. oceanic crust thin layer of the Earth that sits beneath ocean basins. ocean trench remnant of oceanic crust (certain igneous rocks) embedded in continental crust. orogeny the way mountains are formed.

outgas to release a gas that was dissolved, trapped, frozen or absorbed in another material. planet platform Noun ancient rocks that formed as part of continental crust, now overlain with sediment and sedimentary rock, located in the interior of continents. rock natural substance composed of solid mineral matter. sediment rock formed from fragments of other rocks or the remains of plants or animals. shield Noun ancient rocks that formed as part of continental crust and are located in the interior of continents. sial rocks, mostly silicates and aluminum, making up most of Earth's continental crust. silica chemical compound (SiO2) that makes up most of the Earth's rocks. silicate Noun most common group of minerals, all of which include the elements silicon (Si) and oxygen (O). sima rocks, mostly silicates and magnesium, making up most of Earth's oceanic crust. subduction process of one tectonic plate melting, sliding, or falling beneath another. subduction zone area where one tectonic plate slides under another. submersible small submarine used for research and exploration. sulfide (S2-) negatively charged ion of sulfur, or a chemical compound containing such an ion.

tectonic activity movement of tectonic plates resulting in geologic activity such as volcanic eruptions and earthquakes. tectonic plate Noun massive slab of solid rock made up of Earth's lithosphere (crust and upper mantle). Also called lithospheric plate. temperature one of the four planets closest to the sun: Mercury, Venus, Earth, or Mars. transition zone Noun areas in the Earth's interior between the upper mantle, near the Earth's crust, and the lower mantle, near the Earth's core. uniform exactly the same in some way. universe all known matter, energy, and space. viscous liquid that is thick and sticky. volcano Noun an opening in the Earth's crust, through which lava, ash, and gases erupt, and also the cone built by eruptions. High School Earth Science/Inside Earth - Wikibooks, open books for an open world High School Earth Science/Inside Earth From Wikibooks, open books for an open world This is the latest reviewed version , checked on 9 November 2016. There is 1 pending change awaiting review. (+) Quality: minimal 9 Points to Consider Plate tectonics is the unifying theory of geology.

This important theory explains why Earth's geography has changed through time and continues to change today. It explains why some places are prone to earthquakes and some are not; why some regions have deadly volcanic eruptions, some have mild ones, and some have none at all; and why mountain ranges are located where they are. Plate tectonic motions affect Earth's rock cycle, climate, and the evolution of life. Plate tectonic theory was developed through the efforts of many scientists during the twentieth century. Before you can learn about plate tectonics, you need to know something about the layers that are found inside Earth. From outside to inside, the planet is divided into crust, mantle, and core. Often geologists talk about the lithosphere, which is the crust and the uppermost mantle. The lithosphere is brittle–it is easily cracked or broken–whereas the mantle beneath it behaves plastically; it can bend. Geologists must use ingenious methods, such as tracking the properties of earthquake waves, to learn about the interior of our planet. Compare and describe each of Earth's layers. Compare some of the ways geologists learn about Earth’s interior. Define lithosphere, oceanic and continental crust.

Describe how heat moves, particularly how convection takes place in the mantle. Compare the two parts of the core and describe why they are different from each other. Exploring Earth's Interior[ edit ] Earth is composed of several layers. On the outside is the relatively cold, brittle crust. Below the crust is the hot, convecting mantle. At the center is the dense, metallic inner core. How do scientists know this? Rocks yield clues, but geologists can only see the outermost rocky layer. Rarely, a rock or mineral, like a diamond, may come to the surface from deeper down in the crust or the mantle. Mostly, though, Earth scientists must use other clues to figure out what lies beneath the planet's surface. One way scientists learn about Earth's interior is by looking at seismic waves (Figure 6.1). Seismic waves travel outward in all directions from where the ground breaks at an earthquake. There are several types of seismic waves, each with different properties. Each type of wave moves at different speeds through different types of material and the waves bend when they travel from one type of material to another. Some types of waves do not travel through liquids or gases and some do.

So scientists can track how seismic waves behave as they travel through Earth and can use the information to understand what makes up the planet's interior. Much more about earthquakes and seismic waves will be presented in the Earthquakes lesson. Figure 6.1: Different types of seismic waves bend or even disappear as they travel encounter the different properties of the layers that make up Earth's interior. Letters describe the path of an individual P wave or S wave. Scientists also learn about Earth's interior from rocks from outer space. Meteorites are the remains of the material that the early solar system formed from. Some iron and nickel meteorites are thought to be very similar to Earth's core (Figure 6.2). For this reason they give scientists clues as to the core's makeup and density. An iron meteorite is the closest thing to a sample of the core that scientists can hold in their hands! Figure 6.2: An iron meteorite, thought to be similar to Earth's core. Crust and Lithosphere[ edit ] Of course, scientists know the most about Earth's outermost layer and less and less about layers that are found deeper in the planet's interior (Figure 6.3).

Earth's outer surface is its crust; a thin, brittle outer shell made of rock. Geologists call the outermost, brittle, mechanical layer the lithosphere. The difference between crust and lithosphere is that lithosphere includes the uppermost mantle, which is also brittle. Figure 6.3: A cross section of Earth showing the following layers: (1) crust (2) mantle (3a) outer core (3b) inner core (4) lithosphere (5) asthenosphere (6) outer core (7) inner core. The lithosphere is made of the crust plus the uppermost part of the mantle. The asthenosphere is directly under the lithosphere and is part of the upper mantle. The crust is the very thin, outermost solid layer of the Earth. The crust varies tremendously; from thinner areas under the oceans to much thicker areas that make mountains. Just by looking around and thinking of the places you’ve been or seen photos of, you can guess that the crust is not all the same. Geologists make an important distinction between two very different types of crust: oceanic crust and continental crust. Each type has its own distinctive physical and chemical properties.

This is one of the reasons that there are ocean basins and continents. Oceanic crust is relatively thin, between 5 to 12 kilometers thick (3 to 8 miles). This crust is made of basalt lavas that erupt onto the seafloor. Beneath the basalt is gabbro, an igneous intrusive rock that comes from basalt magma but that cools more slowly and develops larger crystals. The basalt and gabbro of the oceanic crust are dense (3.0 g/cm3) when compared to the average of the rocks that make up the continents. Sediments cover much of the oceanic crust, primarily rock dust and the shells of microscopic sea creatures, called plankton. Near shore, the seafloor is thick with sediments that come off the continents in rivers and on wind currents. Continental crust is much thicker than oceanic crust, around 35 kilometers (22 miles) thick on average. Continental crust is made up of many different rocks of all three major types: igneous, metamorphic, and sedimentary. The average composition of continental crust is about that of granite.

Granite is much less dense (2.7 g/cm3) than the basalt and gabbro of the oceanic crust. Because it is thick and has relatively low density, continental crust rises higher above the mantle than oceanic crust, which sinks into the mantle to form basins. When filled with water these basins form the planet's oceans. Since it is a combination of the crust and uppermost mantle, the lithosphere is thicker than the crust. Oceanic lithosphere is about 100 kilometers (62 miles) thick. Continental lithosphere is about 250 kilometers (155 miles) thick. Mantle[ edit ] Beneath the crust lies the mantle. Like the crust, the mantle is made of rock. The mantle is differentiated from the crust by an increase in rock density as indicated by a sudden increase in seismic wave velocities. Evidence from seismic waves and meteorites let scientists know that the mantle is made of iron and magnesium-rich silicate minerals that are part of the rock peridotite. These types of ultramafic rocks are rarely found at Earth’s surface. One very important feature of the mantle is that it is extremely hot.

Although the higher temperatures far exceed the melting points of the mantle rocks at the surface the mantle is almost exclusively solid. The heat in the mantle is mainly due to heat rising from the core. Through the process of conduction, heat flows from warmer objects to cooler objects until all are the same temperature. Knowing the ways that heat flows is important for understanding how the mantle behaves. Heat can flow in two ways within the Earth. If the material is solid, heat flows by conduction, and heat is transferred through the rapid collision among atoms. If a material is fluid and able to move—that is, it is a gas, liquid, or a solid that can move (like toothpaste)—heat can also flow by convection. In convection, currents form so that warm material rises and cool material sinks. This sets up a convection cell (Figure 6.4). Figure 6.4: In a convection cell, warm material rises and cool material sinks. In mantle convection, the heat source is Earth's core. Convection occurs when a pot of water is heated on a stove. The stove heats the bottom layer of the water, which makes it less dense than the water above it, so the warmer bottom water rises.

Since the layer of water on the top of the pot is not near the heat source, it is relatively cool. As a result, it is denser than the water beneath it and so it sinks. Within the pot, convection cells become well established as long as there is more heat at the bottom of the pot than on the top. Convection cells are also found in the mantle. Mantle material is heated by the core and so it rises upwards. When it reaches the surface of the Earth, it moves horizontally. As the material moves away from the core's heat, it cools. Eventually the mantle material at the top of the convection cell becomes cool and dense enough that it sinks back down into the deeper mantle. When it reaches the bottom of the mantle, it travels horizontally just above the core. Then it reaches the location where warm mantle material is rising, and the mantle convection cell is complete. The relationship between mantle convection and plate tectonics will be discussed in the final section of this chapter. Core[ edit ] At the planet's center lies a dense metallic core. Scientists know that the core is metal for two reasons: The first is that some meteorites are metallic and they are thought to be representative of the core.

The second is that the density of Earth's surface layers is much less than the overall density of the planet. We can calculate Earth's density using our planet's rotation. If the surface layers are less dense than the average for the planet, then the interior must be denser than the average. Calculations indicate that the core is about 85% iron metal with nickel metal making up much of the rest. These proportions agree with those seen in metallic meteorites. Seismic waves indicate that the outer core must be liquid and the inner core must be solid. If Earth's core were not metallic, the planet would not have a magnetic field. Metal conducts electricity, but rock—which makes up the mantle and crust—does not. The best conductors are metals that can move, so scientists assume that the magnetic field is due to convection in the liquid outer core. These convection currents form in the outer core because the base of the outer core is heated by the even hotter inner core. The Earth is made of three layers: the crust, mantle and core. The brittle crust and uppermost mantle are together called the lithosphere. Beneath the lithosphere, the mantle is solid rock that can flow, or behave plastically.

The hot core warms the base of the mantle, which cause mantle convection. Mantle convection is very important to the theory of plate tectonics. List two ways that scientists learn about what makes up the planet’s interior. What types of rock make up the oceanic crust? What types of rock make up the continental crust? List two reasons that scientists know that the outer core is liquid. Describe the properties of each of these parts of the Earth's interior: lithosphere, mantle, and core. What are they made of? How hot are they? What are a few of their physical properties? Suppose that Earth's interior contains a large amount of lead. Based on your prior knowledge, how dense is lead? Would the lead be more likely to be found in the crust, mantle, or core? When you put your hand above a pan filled with boiling water, does your hand warm up because of convection or conduction? If you touch the pan, does your hand warm up because of convection or conduction? Based on your answers, which type of heat transfer moves heat more easily and efficiently?

Question: What do we call the layer of the Earth between its crust and its core?
Answer: Mantle