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In geology, the crust is the outermost solid shell of a rocky planet or natural satellite, which is chemically distinct from the underlying mantle. The crusts of Earth, the Moon, Mercury, Venus, Mars, Io, and other planetary bodies have been generated largely by igneous processes, and these crusts are richer in incompatible elements than their respective mantles.

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https://earthquake.usgs.gov/earthquakes/

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http://world-geography-games.com/earth.html

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http://geology.com/rocks/

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tectonic plates

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the prediction of earthquakes and volcanoes

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BBC - GCSE Bitesize: Predicting and preparing for volcanoes

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A secondary school revision resource for GCSE Geography, looking at how earthquakes and volcanic eruptions are predicted and managed.

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Insecticide kills insects

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Background on Plate Movement

Do you ever wonder if the crazy thing someone just told you is true? For instance, you may have heard that person declare that at some point in the near future, California is going to break off and fall into the ocean. My older brother told me that the Golden State is hanging off the end of the continent and will fall into the Pacific Ocean during the next big earthquake. Do the tectonic plates, or giant pieces of the Earth's crust that fit together and move around on the Earth's surface, really move? If so, what causes them to move? The best stories are often based on fact, so it is helpful to know what is real versus what is not. Yes, tectonic plates move, and the mechanism that causes them to move is the subject of this lesson.

The part of my brother's story that is true is that the Western part of California, west of the San Andreas Fault, is moving in a different direction than the rest of the continent. The Western part of California is moving northwest at the rate of several centimeters per year. Looking to the future, California will indeed one day separate from the rest of North America and become an island. Where I think my brother got confused is the mechanism that will cause this to occur.

First of all, it is important to know that the Earth's crust is broken up into large pieces called tectonic plates. Remember, tectonic plates are giant pieces of the Earth's crust that fit together and move around on the Earth's surface. This movement can be observed and measured using GPS systems, and the edges of the plates can be detected, as their edges can be seen. We also know that these plates move around with respect to one another. Earthquakes and volcanoes are the results of such plate movement. One question geologists have been trying to answer is: what is causing the plates of the Earth to move? This can be a challenging question because we are not able to get into the Earth's interior to observe it. There are several mechanisms that scientists have developed based on the observations of the plates and a deeper understanding of the inner layers of the Earth. These mechanisms operate at different points in the Earth and very well could complement each other, each assisting in moving the plate in its own fashion.

Thermal Convection

Scientists believe that one of the primary forces behind plate movement is thermal convection. Thermal convection is when heat from the core of the Earth is transferred to the surface of the Earth by the mantle. The mantle is the thick, mostly solid layer of the Earth between the crust and the core. Thermal convection works a lot like a pot of boiling water, which can be seen in this animation.

In convection, heat from the stove warms up the water closest to the stove, causing the water to expand and rise. Cooler water near the surface of the pot sinks to take the place of the rising water. In doing so, a current of water is set up flowing toward the surface and back down again. Using this model, the stove is like the core and the water is the liquid mantle that rotates. The plates on the Earth's surface would be floating on top of the water. These currents push the plates along according to the direction of flow. Geologists think that this same phenomenon is what is happening inside the Earth. Liquid rock near the mantle is heated and rises toward the crust. The rock near the surface is cooler and sinks back down toward the core. This forms the same type of convection current that causes the plates to move. Scientists believe that this cycle of rising from the core to the crust and back again takes thousands of years to complete.

At the top of the mantle, the rock encounters the thin crust, and, as it pushes it aside, lava flows out from the mantle to form new oceanic crust. As this happens, the plates smash into each other, slide past each other or are pushed under another plate. This movement of the plate along with the upwelling of the mantle by the convection currents may also cause secondary actions that assist in plate movement.

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causes of tectonic plate movement - video & lesson transcript | study.com

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Causes of Tectonic Plate Movement - Video & Lesson Transcript | Study.com

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Do you ever wonder if the crazy thing someone just told you is true? For instance, you may have heard that person declare that at some point in the near future, California is going to break off and fall into the ocean.

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plate boundaires

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Introduction to Plate Boundaries

I hope you have never been in a car accident, but I know we all have seen one in our lives. If you have watched many movies, you almost certainly have. Have you noticed how even when the car is no longer at the accident site, you can tell what happened to it - like where it was impacted, how fast it was going (or the other car was going), and what part was hit first? Even without impacts, perhaps you can piece together what happened when a scratch shows up on the side of the car. As tectonic plates of the earth, or giant pieces of the earth's crust, move and crash into each other, similar tell-tale signs show up to give us some ideas about how they move with relation to each other.

The theory of plate tectonics states that the crust of the earth is broken up into large pieces, or plates, that move around by floating on top of the liquid layer of the earth known as the mantle. This process is driven by convection currents within the mantle. Convection currents are formed by hot magma near the core rising towards the surface, while cooler magma near the crust sinks, setting up a current that causes the plates to move. These currents are the primary driving force behind plate movement. This theory was the result of decades of work and observations made of the earth's surface. It is still the first model to neatly explain all the pieces of data scientists couldn't explain when they thought the surface of the earth was stationary.

The map above may seem confusing at first, but the main thing is that the colored lines show the lines where the crust is broken up into many different plates. Most are named after the continents that are contained on them.

Some plates are entirely oceanic crust, or crust under the ocean, while others are a combination of oceanic and continental crust, which is crust of the continents. The boundary where two separate plates meet is where all the action occurs and is called a fault. A fault is a crack in the earth's crust resulting from the movement of the two plates.

Getting back to the example of cars, when two cars are next to each other, there are three possible ways for the cars to move with relation to each other. Plates act in a similar manner.

Divergent Boundary

The first way two cars can move relative to each other is in divergent directions, like passing a car going the other way. Plates also can pull apart from each other. This is known as a divergent boundary. A divergent boundary is a fault where the two plates are moving away from each other.

Now, as plates pull apart, several things may occur. First of all, volcanic activity is common in these areas since mantle easily moves to the surface through the thin, fractured rock as it separates. Volcanoes are a sign of a divergent boundary. This happens all along the mid-ocean ridge where magma is constantly streaming to the surface, creating new ocean floor as the plates separate.

If a continent happens to be a place where a divergent boundary occurs, then the continent will begin to be torn apart as the sides of the plates separate, creating a rift valley. The African Rift Valley in East Africa is an example of this occurrence. Eventually, the ocean will separate East Africa from the rest, making a large island.

Convergent Boundary

A second way cars interact (unfortunately) is by colliding. When cars impact each other or another solid object, the energy is transferred to the cars themselves, showing up as dents, ripples, or cracks. Plates also show tell-tale signs of colliding, too, depending on the kind of crust colliding.

Remember that at divergent boundaries, new crust is being made, but the earth is not getting larger. Why not? Well, at the opposite ends, crust is being pushed into the earth's interior by colliding plates and being re-melted at the same rate new crust is formed. This happens at a convergent boundary. A convergent boundary is a boundary where two separate plates are pushing into each other.

There are two kinds of surface features that are associated with a convergent boundary. The first is a deep ocean trench that forms a line of the two colliding plates. One plate made of oceanic crust can slide down underneath another plate, forming this narrow, deep trench. This happens because oceanic crust is more dense than continental crust, making it more likely to be pushed back into the mantle. These trenches are the deepest places on the face of the earth, extending over 30,000 feet below the ocean surface. You could take Mount Everest and sink it in the Mariana Trench, the deepest point in the ocean, and still have a mile to the surface of the ocean. That's deep!

As one plate is forced under the other one, it begins to melt, and a line of volcanoes forms in a parallel line to the trench. If the other plate is oceanic crust, the line of volcanoes will become islands, like the Philippines, and if it is continental crust, then it will become a line of volcanic mountains, like the Cascade Range in the western U.S. or the Andes Mountains in South America.

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and transform boundaries - video & lesson transcript | study.com

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Plate Boundaries: Convergent, Divergent, and Transform Boundaries - Video & Lesson Transcript | Study.com

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I hope you have never been in a car accident, but I know we all have seen one in our lives. If you have watched many movies, you almost certainly have.

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the behavior of tectonic plates

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Moving Puzzle Pieces

The top layer of Earth is an interesting place. Also known as the 'crust,' this thin, solid layer is much more than meets the eye. If Earth were an apple, the skin of that apple could represent the crust in terms of thickness and location. But unlike an apple skin, Earth's crust isn't one large piece covering the entire planet. Instead, it's broken up into many different pieces called tectonic plates that fit together like a large puzzle.

Also unlike the apple, underneath the solid crust is not a deliciously crispy interior. Instead, directly below the crust, we have a thick liquid layer called the mantle. Because it is liquid, the mantle flows and moves around, which moves the plates sitting on top like pieces of ice on a pond.

When the plates get moved around, they wreak havoc because they crash into, and pull apart from, and rub against each other. And as you can imagine, these interactions can do some pretty serious damage. On Earth, these tectonic events result in dangerous natural disasters around the world, like earthquakes, volcanoes, and tsunamis.

Earthquakes

Earthquakes can and do happen anywhere in the world, but the majority of them occur in a region known as 'The Ring of Fire.' As you'll learn a little later in this lesson, this is also where most of the world's volcanoes are found and where the name comes from.

The reason so many earthquakes occur in these areas is because this is where many of Earth's tectonic plates come together. Earthquakes begin deep underground along plate boundaries. Tension and pressure build up as the plates slide past and bump into each other and sometimes even stick together. Although the plate boundaries themselves may be stuck, the plates keep moving and pulling. Eventually, the pulling becomes too much and the plates suddenly break free from each other, causing an earthquake!

You can think of an earthquake like a game of tug-of-war. If you and your friend are both pulling on opposite ends of the rope and suddenly your friend lets go, all of that tension quickly leaves the rope and down onto the ground you go! An earthquake is very much the same - the plates get stuck together as they move, building up tension. Suddenly, the plates slip past each other and break free, sending that built-up tension through the ground in all directions.

Volcanoes

Plate movement can also cause other natural phenomena, like volcanoes. Under the right conditions, when plates are pushed together or pulled apart, volcanoes are created, which is why they tend to occur in the same place as earthquakes.

When tectonic plates spread apart from each other, hot magma rises up and fills the space between. As it cools, it forms new land, either on the continents or on the seafloor, depending on where the plates are located.

When the plates come together, one of them may get pulled under the other one, getting recycled back into Earth's interior. During this process, called subduction, the piece of crust getting pulled under is melted and turned into magma - the very magma that erupts from a volcano!

As the magma comes out of the volcano opening, it cools and builds the volcano even taller. The more subduction, the more buildup. Volcanic ranges like the Sierra Nevada and Cascade in the U.S. and the Andes in South America were formed from plate movement and rising magma.

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tsunamis & volcanic eruptions - video & lesson transcript | study.com

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How Plate Movement Affects Earthquakes, Tsunamis & Volcanic Eruptions - Video & Lesson Transcript | Study.com

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The top layer of Earth is an interesting place. Also known as the 'crust,' this thin, solid layer is much more than meets the eye. If Earth were an apple, the skin of that apple could represent the crust in terms of thickness and location.

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This HD dramatic video choreographed to powerful music introduces the viewer/student to earthquakes and tsunamis. It is designed as a motivational "trailer" to be shown in classrooms by Earth Science and Physical Science teachers in middle school, high school and college as a visual Introduction to the power of Earth's tectonic crust.

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earthquakes and volcanoes

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What's on the Inside?

Have you ever been on a quest for that perfect melon? We tap it, push on the ends, listen to it, shake it, smell it, and all kinds of things. Why do we do this? We do it because we try to find out what's on the inside. Is it ripe fruit - or something not good or overripe? We try to use our senses to gain as much information as possible about this piece of fruit to determine what it's like on the inside. And hopefully, we are successful. Yum!

One of the first questions that gets asked when people start learning about the five layers of the earth is, 'How do people know what the interior layers of the earth are like if we can't get there to see?' This answer is very similar to searching for the perfect piece of fruit and is the subject of this lesson.

While we can't pick up the earth and shake it, and smelling it probably wouldn't help us much, tapping on the earth and listening to the sounds it makes does have some possibility. We can do this by exploring earthquakes and volcanoes! We hear about them and the destruction that they can cause, like Mt. St. Helens, Vesuvius, and Pinatubo.

In a volcano, melted rock called magma breaks through the crust and begins to pile up on the surface, forming any one of a variety of cones. Volcanoes can erupt in one of two ways; either suddenly and violently, like Mt. St. Helens or Pinatubo, or slowly and gradually, like the Hawaiian volcanoes.

One of the factors that determines whether they explode or not is the amount of silica in the magma. The more silica present, the more solid it can become, plugging up the chambers under the ground. Pressure then builds up, causing the catastrophic eruptions seen in Mt. St. Helens, Pinatubo, or Krakatoa. Magma with relatively little silica is much more fluid and will flow more like water as the volcanoes in Hawaii do. Either way, scientists can get a glimpse of the contents of the layers under the earth's crust by studying the debris that erupts from these .

Another theory about why some volcanoes erupt violently and others do not gives us some understanding about the content of gases in the earth. Sometimes, the magma rising to the surface of the earth happens quite fast. When it does, the gas bubbles in the magma begin to expand as the pressure decreases. When the magma reaches the surface, there is a large release of the pent-up gases, causing the volcano to erupt - much like opening a soft drink that has been shaken.

In an eruption that is nonexplosive, scientists think most of the gas has had a chance to be released, as the magma has risen to the surface more slowly. This leaves little gas to be released, and just the magma is emitted from the earth.

S Waves

This would be like shaking the end of a Slinky up and down and seeing the waves travel along it. These waves travel only through solids, so scientists can track where these types of waves show up - and how they are absent in other places. From this information, they can figure out which layers of the earth are solid and which are liquid.

P Waves

Another type of wave is a compression wave, and are also known as P waves, and they are the faster of the two types. P Waves are waves that travel through the layers of the earth by compressing the matter they travel through.

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earthquakes and volcanoes: evidence of earth's inner layers - video & lesson transcript | study.com

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Earthquakes and Volcanoes: Evidence of Earth's Inner Layers - Video & Lesson Transcript | Study.com

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Have you ever been on a quest for that perfect melon? We tap it, push on the ends, listen to it, shake it, smell it, and all kinds of things. Why do we do this? We do it because we try to find out what's on the inside.

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The Earth is made of layers of different material. We live on the crust, which is the source of all rock and metals we use for building everything from houses to computer chips. The Earth is surrouded by the atmosphere

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Global Warming: The GlobalGlobal Warming: The Global WarningWarning Biology 2201Biology 2201

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Volcanoes and earthquakes. Inside the Volcano.

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Visit: http://www.world-earthquakes.com VERY IMPORTANT: This video is for education purpose only!

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Human-generated emissions of carbon dioxide and other greenhouse gases affect important global climate processes. Understanding the greenhouse effect, carbon cycle, climate forcing, and climate feedbacks helps to explain how and why climate is changing.

The greenhouse effect is a natural warming process. Carbon dioxide and certain other gases are always present in the atmosphere. These gases create a warming effect that has some similarity to the warming inside a greenhouse, hence the name "greenhouse effect."

Increasing the amount of greenhouse gases intensifies the greenhouse effect. Higher concentrations of these gases trap more infrared energy in the atmosphere than occurs naturally. The additional heat further warms the atmosphere and Earth's surface.
Image based on a figure from US EPA. For more information, see America's Climate Choices.
Larger Image

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Human-generated emissions of carbon dioxide and other greenhouse gases affect important global climate processes. Understanding the greenhouse effect, carbon cycle, climate forcing, and climate feedbacks helps to explain how and why climate is changing. The greenhouse effect is a natural warming process. Carbon dioxide and certain other gases are always present in the atmosphere.

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https://msnucleus.org/membership/html/k-6/pt/plate/4/ptpt4_3a.html

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The greenhouse effect:
Gases in the atmosphere keeps the earth warm. Carbon dioxide is also a greenhouse gas. However, the amount of carbon dioxide is increasing because most fuels produce carbon dioxide when they burn. The increasing amount of CO2 will lead to global warming as the earth gets warmer.

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Wegeners theory of continental drift

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http://www.bbc.co.uk/bitesize/ks3/science/environment_earth_universe/rock_cycle/revision/1/

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http://www.bbc.co.uk/schools/gcsebitesize/geography/natural_hazards/earthquakes_rev1.shtml

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Bill Nye  The Science Guy   S01E02   Earth's Crust

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http://www.bbc.co.uk/schools/gcsebitesize/science/aqa_pre_2011/oils/changesrev2.shtml

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http://www.bbc.co.uk/schools/gcsebitesize/geography/natural_hazards/tectonic_plates_rev1.shtml

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Wegener's theory  of the continental drift

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Wegener's theory  of the continental drift

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http://www.bbc.co.uk/schools/gcsebitesize/science/21c_pre_2011/earth_and_space/continentaldriftrev1.shtml