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First thing's first. Let's take a look at how Earth is structured from the ground beneath us, all the way to the core. Place your mouse cursor over the different terms to learn about the layers.

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Interactives . Dynamic Earth . Earth’s Structure

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In the early part of the 20th century, geologists studied the vibrations (seismic waves) generated by earthquakes to learn more about the structure of the earth’s interior. They discovered that it is made up of these distinct layers: the crust, the mantle, and the core.

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You may stop the video at 4:30. This is a short video to help visualize Earth's structure.

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Everything You Need to Know About Planet Earth

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Now that we know how Earth is layered, let's take a look at the top-most layers. Content available in English and Spanish.

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Plate Tectonics: An Introduction | PBS LearningMedia

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In the early 1900s, most geologists thought that Earth's appearance, including the arrangement of the continents, had changed little since its formation. This video segment, adapted from the "Earth Explorer" episode of Discovering Women, describes the impact the theory of plate tectonics has had on our understanding of Earth's geological history, as we have become aware of our planet's ever-changing nature.

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Plate interaction comes in many forms, and can create many of Earth's amazing structures (e.g. volcanoes). Use this simulation to create different plate boundary scenarios.

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A short video on plate tectonics. What local fault line is addressed here? Notice the transform boundary that is used as an example.

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A closer look at the San Andreas fault. Drag and drop the labels to the correct place along the San Andreas Fault. This is an EL friendly activity to practice terminology.

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An online resource from the Geological Society, aimed at students aged 14 - 16. Learn how the theory of plate tectonics has developed, what happens at different plate margins, and the tectonic history of the UK.

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Volcanoes occur as a result of plate movement, among other reasons. Take a look at this video to learn more about how this natural hazard affects our planet.

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Please read this short article and keep in mind that we covered climate change in a past unit. How is the geosphere (volcanoes) influencing the atmosphere (climate)?

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Volcanic eruptions are responsible for releasing molten rock, or lava, from deep within the Earth, forming new rock on the Earth's surface. But eruptions also impact the atmosphere.

The gases and dust particles thrown into the atmosphere during volcanic eruptions have influences on climate. Most of the particles spewed from volcanoes cool the planet by shading incoming solar radiation. The cooling effect can last for months to years depending on the characteristics of the eruption. Volcanoes have also caused global warming over millions of years during times in Earth's history when extreme amounts of volcanism occurred, releasing greenhouse gases into the atmosphere.

Even though volcanoes are in specific places on Earth, their effects can be more widely distributed as gases, dust, and ash get into the atmosphere. Because of atmospheric circulation patterns, eruptions in the tropics can have an effect on the climate in both hemispheres while eruptions at mid or high latitudes only have impact the hemisphere they are within.

Below is an overview of materials that make their way from volcanic eruptions into the atmosphere: particles of dust and ash, sulfur dioxide, and greenhouse gases like water vapor and carbon dioxide.

Particles of Dust and Ash

Volcanic ash or dust released into the atmosphere during an eruption shade sunlight and cause temporary cooling. Larger particles of ash have little effect because they fall out of the air quickly. Small ash particles form a dark cloud in the troposphere that shades and cools the area directly below. Most of these particles fall out of the atmosphere within rain a few hours or days after an eruption. But the smallest particles of dust get into the stratosphere and are able to travel vast distances, often worldwide. These tiny particles are so light that they can stay in the stratosphere for months, blocking sunlight and causing cooling over large areas of the Earth.

Sulfur from Volcanoes

Often, erupting volcanoes emit sulfur dioxide into the atmosphere. Sulfur dioxide is much more effective than ash particles at cooling the climate. The sulfur dioxide moves into the stratosphere and combines with water to form sulfuric acid aerosols. The sulfuric acid makes a haze of tiny droplets in the stratosphere that reflects incoming solar radiation, causing cooling of the Earth's surface. The aerosols can stay in the stratosphere for up to three years, moved around by winds and causing significant cooling worldwide. Eventually, the droplets grow large enough to fall to Earth.

Greenhouse Gases Emitted by Volcanoes

Volcanoes also release large amounts of greenhouse gases such as water vapor and carbon dioxide. The amounts put into the atmosphere from a large eruption doesn't change the global amounts of these gases very much. However, there have been times during Earth history when intense volcanism has significantly increased the amount of carbon dioxide in the atmosphere and caused global warming.

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Read this short article on how earthquakes are related to plate tectonics.

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What is an earthquake?
Earthquakes are the shaking, rolling or sudden shock of the earth's surface. They are the Earth's natural means of releasing stress. More than a million earthquakes rattle the world each year. The West Coast is most at risk of having an earthquake, but earthquakes can happen in the Midwest and along the East Coast. Earthquakes can be felt over large areas although they usually last less than one minute. Earthquakes cannot be predicted - although scientists are working on it!

Click Here to learn more about earthquakes from USGS.

What causes an earthquake?
There are about 20 plates along the surface of the earth that move continuously and slowly past each other. When the plates squeeze or stretch, huge rocks form at their edges and the rocks shift with great force, causing an earthquake. Think of it this way: Imagine holding a pencil horizontally. If you were to apply a force to both ends of the pencil by pushing down on them, you would see the pencil bend. After enough force was applied, the pencil would break in the middle, releasing the stress you have put on it. The Earth's crust acts in the same way. As the plates move they put forces on themselves and each other. When the force is large enough, the crust is forced to break. When the break occurs, the stress is released as energy which moves through the Earth in the form of waves, which we feel and call an earthquake. (Graphic Credit: Wheeling Jesuit University/NASA Classroom of the Future)

Click Here to see an animation of an earthquake. It's great for kids, because they get to see how it actually happens!

What is a fault?
A fault is an area of stress in the earth where broken rocks slide past each other, causing a crack in the Earth's surface. There are the major types of faults: dip-slip normal, dip-slip reverse, strike-slip, and oblique-slip.

What are plate tectonics?
The theory of plate tectonics is a interesting story of continents drifting from place to place breaking apart, colliding, and grinding against each other. The plate tectonic theory is supported by a wide range of evidence that considers the earth's crust and upper mantle to be composed of several large, thin, relatively rigid plates that move relative to one another. (See plate tectonic graphic above.) The plates are all moving in different directions and at different speeds. Sometimes the plates crash together, pull apart or sideswipe each other. When this happens, it commonly results in earthquakes.

Continental Drift: To see this animation again, just refresh this page! This animation shows you what our planet looked like millions of years ago and what it looks like now! (Graphic Credit: Geology Department at University of California, Berkeley)

What is a seismograph?
A seismograph is an instrument used for recording the intensity and duration of an earthquake.

Click Here to calculate the strength of earthquakes!

What is a tsunami? A tsunami is a large ocean wave usually caused by an underwater earthquake or a volcanic explosion. Tsunamis are NOT tidal waves. Tidal waves are caused by the forces of the moon, sun, and planets upon the tides, as well as the wind as it moves over the water. With typical waves, water flows in circles, but with a tsunami, water flows straight. This is why tsunamis cause so much damage!

Know the Lingo

EPICENTER - The point on the earth's surface directly above the source of the earthquake.

SEISMIC WAVES - The energy created by the quake travels in waves from the epicenter, where they are the strongest. The waves shake buildings, structures and the earth vertically, causing them to move horizontally!

RICHTER SCALE - A measurement of an earthquake's intensity. Each one-point increase on the scale indicates ten times the amount of shaking and 33 times the amount of energy. The energy released by a large earthquake may be equal to 10,000 times the energy of the first atomic bomb.

4

Minor Earthquake

5

Moderate Earthquake

6

Strong Earthquake

7

Major Earthquake

8

Great Earthquake

Richter Scale

Earthquake Safety Tips
BEFORE AN EARTHQUAKE: Have a disaster plan. Emergency preparedness can save lives. Choose a safe place in every room. It's best to get under a sturdy piece of furniture like a table or a desk where nothing can fall on you. Practice DROP, COVER AND HOLD ON! Drop under something sturdy, hold on, and protect your eyes by pressing your face against your arm. If you live in an earthquake prone area, bolt tall furniture to the wall and install strong latches to cupboards. Prepare a first aid kit for your home. By taking special precautions and checking for hazards before a disaster strikes, you will be much more likely to stay safe. DURING AN EARTHQUAKE: DROP, COVER AND HOLD ON! Stay indoors until the shaking stops. Stay away from windows. If you're in bed, hold on and stay there, protecting your head with a pillow. If you're outdoors, find a clear spot away from buildings, trees and power lines. Then, drop to the ground. If you're in a car, slow down and drive to a safe place. Stay in the car until the shaking stops.

AFTER THE SHAKING STOPS: Check for injuries. Inspect your home for damage. Eliminate fire hazards, so turn off the gas if you think its leaking. Expect aftershocks. Each time you feel one, DROP, COVER AND HOLD ON.
Earthquake Activities
Lesson Plan: Here is a great lesson plan on learning about how thrust faults are responsible for the uplift of many mountain ranges across the world, including the Los Angeles Basin. This is a great lesson plan for middle and high school students.

Lesson Plan: Here is a great lesson plan keeping track of earthquakes around the world. In this activity, kids keep a record of the location of earthquakes for a week and learn about plate tectonics.

Earthquake Experiment: Here is a great experiment that explains how to prepare for an earthquake.Science Fair Ideas: Here is a list of science fair project ideas that deal with earthquakes.

Science Fair Project Ideas: Here is a complete list of science fair project ideas. Discover the science behind the weather that impacts us every day.

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Weather Wiz Kids weather information for kids

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Weather Wiz Kids is a fun and safe website for kids about all the weather info they need to know. It contains tools for weather education, including weather games, activities, experiments, photos, a glossary and educational teaching materials for the classroom.

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Earthquake are a result of a release of Energy from within the Earth. Can you guess where the Earthquake is starting? Give this game a shot.

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In this free science game, players locate an earthquake's epicenter! Can you ride the seismic waves? Or will triangulation get the better of you?

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Check out recorded seismic activity through time!

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The last natural hazard we'll cover is called liquefaction.

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Liquefaction is a process that temporarily turns firm ground into a liquid. During the Canterbury earthquakes of September 2010 and February 2011, liquefaction caused silt and fine sand to boil up and bury streets and gardens and caused buildings and vehicles to sink. This was a new phenomenon for most New Zealanders, yet it has been a feature during earthquakes throughout this country's history. There is evidence of liquefaction in most of the largest earthquakes since the 1840s, including the Hawke's Bay quake of 1931.

Next time you are on a sandy beach, walk across some wet sand a little back from the water's edge. It's firm walking, though you might leave footprints. Now stand still, wriggle your toes and feet. If conditions are right, you could sink a little as the sand around your feet becomes sloppy. This is similar to what happens during liquefaction.

Causes of liquefaction

Over thousands of years, rivers deposit layers of silt and sand in many places, especially in low-lying ground and near the coast. The top layer of sediment can become flat, firm and dry - ideal for building on - but this often hides layers of waterlogged sediment beneath.

Severe shaking in an earthquake puts pressure on the silt and water particles in these waterlogged layers, turning once firm sediment into a liquid. Pressure on the liquefied layer is increased by the ground above it pushing down. Water fountains and sand boils can burst upwards through any cracks.

It's a bit like using a coffee plunger carelessly. If you push the plunger down too quickly, the water and coffee grounds are put under pressure. If they find a gap around the edge of the plunger they spray up all over the bench or table.

Damage from liquefaction

Liquefaction only happens when underlying waterlogged silts are present and when shaking is severe. When the ground becomes liquid, it can no longer support the weight of buildings, so these tend to sink. The overlying ground can also sink, spread and crack. Underground pipes and tanks float and break. Power poles fall and break cables. During the 2010 and 2011 Canterbury earthquakes, over 400 000 tonnes of silt came to the surface, covering streets and gardens in several suburbs.

Liquefaction is not just a New Zealand problem. In 1995, the Japanese city of Kobe suffered extensive damage from an earthquake. The port had been built on artificial islands made of relatively loose sand and silt, and many buildings collapsed during the liquefaction that happened here.

Reducing liquefaction hazards

The Museum of New Zealand Te Papa Tongarewa is on the waterfront in Wellington. The ground was considered to be at risk from liquefaction in the event of an earthquake, so it was compacted before building started. This involved dropping 30-tonne weights on the ground over 50 000 times, which took several months. Together with base isolators, this gives Te Papa considerable protection during an earthquake. Ground compaction also worked to reduce liquefaction damage in some residential areas of Christchurch during the 2010 and 2011 earthquakes.

Another way to reduce damage in areas at risk from liquefaction is to place buildings on concrete pillars that go through the sediment layers to firmer layers beneath. If the liquefaction-prone layers are shallow enough, they can be dug out and replaced with a firmer fill.

Nature of science

Useful links

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Liquefaction is a process that temporarily turns firm ground into a liquid. During the Canterbury earthquakes of September 2010 and February 2011, liquefaction caused silt and fine sand to boil up and bury streets and gardens and caused buildings and vehicles to sink.

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When watching this video, notice the connection between liquefaction and Earthquakes

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An activity to explore how liquefaction works. All you need is some sand, water, and a container to put it in. This is an ELL/IEP friendly activity.

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Post Author: Nate Gagnon & Justin Riely

Plastic container

Materials to put in the sand that both float and sink (Blocks, rocks, Lego structures, ping pong balls, etc.)

Fill the container with sand. Add water to the sand until it is very wet, but the water does not pool up. Place your objects on top of the sand, and even bury a few too! When you are ready, simulate your earthquake by banging on the container and shaking it rapidly.

Soil can behave like a fluid when it is completely soaked with water and shaken. This process is called liquefaction, and it reduces the strength and stiffness of the soil during earthquakes. Liquefaction is one of the main sources of structural damage caused by earthquakes worldwide.

Liquefaction occurs when water fills the spaces between individual soil particles and repeated shaking like an earthquake occurs. The water exerts pressure on the soil particles and changes how tightly the soil particles are able to pack together. Normally, this water pressure is low, but during an earthquake the water pressure increases due to the shaking motion. As this water pressure increases, it will become strong enough to separate the soil particles from one another and cause the soil to "liquefy," or move like a fluid. Liquified or fluid soil does not have enough strength or integrity to hold up building foundations or bridges, causing buildings to sink below the surface or underground structures like a septic tank to float to the surface.

Ask Your Young Scientists:

How does the sand look before we shake the container? What about afterwards?

What do you notice happening to the sand when we shake the container? What about the objects we added?

Which materials stayed where we put them, which ones sank, and which ones floated to the surface during the earthquake?

Try different materials both on top of and under the sand. Which ones go up and which go down?

Try shaking the container softer or harder, what happens to the materials we put in our bin?

Change the amount of water in the sand. How does that affect the location of our materials during our earthquake?

We want to see what you try at home. Share your creation with us on social media by using the #ScienceAtPlay and tagging @CTScienceCenter.

Justin Riley is the Teen Programs Coordinator and STEM Educator at the Connecticut Science Center, where he works closely with high school students giving them access to STEM and leadership programming. Justin graduated from the University of Hartford with his Bachelors in Electrical Engineering Technology and a Masters degree in Counselor Education and Student Development. Justin has worked several years with a wide range of students from pre-k to college. His love of engineering and mentoring led him to the Connecticut Science Center where he gets to use his many talents to work and connect with the students in the Greater Hartford area. When he is not helping to run the teen program, he spends his time traveling and spending close time with family and friends.

Nate Gagnon is a Public Programs Educator at the Connecticut Science Center. In his role he creates exciting educational programs and demonstrations that highlight science and STEM careers. You can find him in our galleries with fun activities that you and your family can enjoy.

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﻿ Materials to Collect Plastic container Sand Water Materials to put in the sand that both float and sink (Blocks, rocks, Lego structures, ping pong balls, etc.) Build it! Fill the container with sand. Add water to the sand until it is very wet, but the water does not pool