Earthquakes...

Earthquakes...

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.

Because people are frequently left relying on themselves for awhile after an earthquake, it is a good idea to have an earthquake survival kit ready. Everyone who lives in an area where large earthquakes can happen should have one of these kits in their home.

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)

Click Here to learn more about plate tectonics and the drifting of our continents.

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!






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

Click Here to get the latest tsunami warning information from the NWS.

Click Here for tsunami safety information.

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.

Click Here to see if there has been any recent earthquake activity across the U.S.

Richter Scale

4	Minor Earthquake
5	Moderate Earthquake
6	Strong Earthquake
7	Major Earthquake
8	Great Earthquake

Click Here to learn about cool earthquake facts!

Earthquake Safety Tips
BEFORE AN EARTHQUAKE: Have a disaster plan. 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 anemergency survival 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.

Climate

Climate...

What is climate?
Climate is the average weather usually taken over a 30-year time period for a particular region and time period. Climate is not the same as weather, but rather, it is the average pattern of weather for a particular region. Weather describes the short-term state of the atmosphere.


What is our climate system?

Atmosphere	The atmosphere covers the Earth. It is a thin layer of mixed gases which make up the air we breathe. This thin layer also helps the Earth from becoming too hot or too cold.
Oceans	Oceans cover about 70 percent of Earth's surface. Their large size and thermal properties allow them to store a lot of heat.
Land	Land covers 27 percent of Earth's surface and land topography influences weather patterns.
Ice	Ice is the world's largest supply of freshwater. It covers the remaining 3 percent of Earth's surface including most of Antarctica and Greenland. Ice plays an important role in regulating climate, because it is highly reflective.
Biosphere	The biosphere is the part of Earth's atmosphere, land, and oceans that supports any living plant, animal, or organism. It is the place where plants and animals, including humans, live.

What is weather?
The weather is just the state of the atmosphere at any time, including things such as temperature, precipitation, air pressure and cloud cover. Daily changes in the weather are due to winds and storms. Seasonal changes are due to the Earth rotating around the sun.


What causes weather?
Because the Earth is round and not flat, the Sun's rays don't fall evenly on the land and oceans. The Sun shines more directly near the equator bringing these areas more warmth. However, the polar regions are at such an angle to the Sun that they get little or no sunlight during the winter, causing colder temperatures. These differences in temperature create a restless movement of air and water in great swirling currents to distribute heat energy from the Sun across the planet. When air in one region is warmer than the surrounding air, it becomes less dense and begins to rise, drawing more air in underneath. Elsewhere, cooler denser air sinks, pushing air outward to flow along the surface and complete the cycle.

Why do mountains affect weather and climate?
There are two sides to a mountain: wayward and leeward. Whenever it is raining, the wayward side gets the rain. As a cloud goes up the mountain, it keeps raining until there is no more water in the cloud. Now, as the cloud starts to go down the other side of the mountain, there is no more precipitation. So, the leeward side of the mountain doesn't get any rain. The flat ground on this side of the mountain is dry and humid.

What is the Water Cycle?
Earth has a limited amount of water. So, that water keeps going around. We call it the water cycle. The water cycle begins with evaporation. Evaporation is when the sun heats up water in rivers, lakes or the ocean. Then turns it into water vapor or steam. The water vapor or steam leaves the body of water and goes into the air. Transpiration is the process by which plants lose water out of their leaves. Condensation is when water vapor in the air gets cold and changes back into water to form clouds. Think of it this way, when you open a cold soda on a hot summer day, your soda will start to sweat as water droplets form on the outside of the can. Precipitation occurs when so much water has condensed that the air can't hold it anymore. This is how we get rain or snow. Collection happens when the precipitation falls and is collected back in the oceans, lakes and rivers. When it falls to the ground, it will soak into the earth and become ground water. This is the water cycle and it just keeps repeating.

Click Here to learn more about the Earth's water cycle.

Why do we have seasons?
As the Earth spins on its axis, producing night and day, it also moves about the Sun in an elliptical (elongated circle) orbit that requires 365 1/4 days to complete. The Earth's axis is tilted at 23.5 degrees and is why we have seasons. When the Earth's axis points towards the Sun, it is summer for that hemisphere. When the Earth's axis points away, winter can be expected.


What is the significance of the Sun to the Earth?
Without the Sun, there would be no weather. Earth is positioned as the third planet, so our temperatures are sustainable for life. The average temperature of Mars is much colder, while Venus is much hotter.

How can you tell what time it is by looking at the Sun?
Because the sun ALWAYS rises in the east and sets in the west, you can tell the time just by looking at where the sun is. When you look east and the sun is on the horizon that means its approximately 6:00am. When the sun is directly above your head that means its noon. When you look to the west and the sun is on the horizon that means its approximately 6:00pm.


Why do we get more sunlight in the summer than in the winter?
You might not have noticed this, but the Earth tilts over slightly. If you have a globe at home or in school, you can see that the line between north and south poles, that goes through the center of the Earth, isn't vertical. It's actually tilting over by about 23 degrees. In our summer, the north pole is pointing towards the Sun so the Sun rises and sets roughly from due east to due west. In winter, the Earth is on the other side of the Sun so the North Pole is pointing away from the Sun. This means the Sun rises and sets more towards the southeast and southwest. You might notice this as you look out of the window. Think back to how high in the sky the sun was during the summer. Compare this to where the sun is during the winter and you'll see it's much lower down towards the horizon. Because the sun is lower down on the horizon, there's less time for it to travel between horizons. There's less distance for it to travel so the sun rises later and sets earlier meaning there's less daylight.


What is the purpose of the Moon?
The tidal effect of the moon helps to recirculate the oceans and keep them from becoming stagnated. The result of which would be catastrophic for advanced forms of life like humans.


Why do the leaves change color?
During the spring and summer the leaves have served as factories where most of the foods necessary for the tree's growth are manufactured. This food-making process takes place in the leaf in numerous cells containing chlorophyll, which gives the leaf its green color. Along with the green pigment are yellow to orange to red pigments as well. Most of the year these colors are masked by great amounts of green coloring. But in the fall, because of changes in the length of daylight and changes in temperature, the leaves stop their food-making process. The chlorophyll breaks down, the green color disappears, and the yellow to orange to red colors become visible and give the leaves part of their fall splendor. The best time to enjoy the autumn color would be on a clear, dry, and cool day.


What is Climate Change?
Climate change represents a change in long-term weather patterns. They can become warmer or colder. Annual amounts of rainfall or snowfall can increase or decrease.

What is Global Warming?
Global warming refers to an average increase in the Earth's temperature, which in turn causes changes in climate. A warmer Earth may lead to changes in rainfall patterns, a rise in sea level, and a wide range of impacts on plants, wildlife, and humans. When scientists talk about the issue of climate change, their concern is about global warming caused by human activities. (Graphic Credit: World Almanac Education Group)




Is the Earth getting warmer?
Yes! The Earth has warmed by about 1ºF over the past 100 years. But why? Well, scientists are not exactly sure. The Earth could be getting warmer on its own, but many of the world's leading climate scientists think that things people do are helping to make the Earth warmer.
Click Here to learn more about Global Warming.

What is the Greenhouse Effect?
The greenhouse effect is the rise in temperature that the Earth experiences because certain gases in the atmosphere like water vapor, carbon dioxide, nitrous oxide, and methane trap energy from the sun. Without these gases, heat would escape back into space and Earths average temperature would be about 60ºF colder and would not be warm enough for humans to live. But if the greenhouse effect becomes stronger, it could make the Earth warmer than usual. (Graphic Credit: EPA)

Click Here to learn about Earth's carbon cycle affected by global warming.

Global Warming may be a big problem, but can you make a difference?
Yes! There are several little things you can do to make a difference. Try carpooling. This will help reduce the amount of fossil fuels going into the atmosphere. Whenever you use electricity, you help put greenhouse gases into the air. Turning off lights, the television, and the computer when you are through with them. Also, planting trees is fun and a great way to reduce greenhouse gases. Trees absorb carbon dioxide, a greenhouse gas, from the air. Finally, don't forget about recycling.

What is El Niño?
El Niño is a climate pattern where the water in the Pacific Ocean near the equator gets hotter than usual and affects the atmosphere and weather around the world. El Niño climate conditions occur every few years, and they are not predictable. El Niño is Spanish for The Little Boy. It refers to the Christ child and was named by Mexican fisherman, who noticed the climate pattern often formed around Christmastime.

In a normal year, the warmest water is in the far western Pacific. This forms thunderstorms. (Graphic Credit: USA TODAY)	In an El Niño year, the warmest water moves eastward across the Pacific. Thunderstorms disrupt the jet stream changing the weather pattern.

What type of a climate pattern do we see with an El Niño?
The climate pattern can change the weather of the United States, particularly in California and the southern states. Usually, El Niño brings more rain and higher temperatures. Also, warm ocean currents come farther north and all kinds of tropical fish can be caught in the waters far north along the United States West Coast. El Niño may also bring warmer than normal winter temperatures to the eastern part of the United States.

What is La Niña?
La Niña is sort of the opposite of El Niño. During a La Niña, the water in the same area along the equator gets colder than usual. This, too, affects weather around the globe and in the U.S. According to scientists, La Niña cycles generally create a more active hurricane season in the Atlantic.

What type of climate pattern do we see with La Niña?
In the United States, La Niña is expected to bring above normal temperatures throughout most of the Southwest and southern Florida in the late summer and fall. These warmer conditions will extend across the Southeast during the winter months. Cooler than normal winter temperatures are expected in the Pacific Northwest. Cooler than normal temperatures are also expected across the Great Lakes and Northeast later in the winter into spring. In addition to temperature effects, La Niña is also expected to affect rainfall. Drier than normal conditions will persist in west Texas, New Mexico and Arizona into October. The late fall and early winter forecasts indicate continued dry conditions throughout much of the southern U.S. and into portions of the Midwest. Above normal precipitation is predicted for much of the Pacific Northwest throughout the fall and into the winter months, and in the Ohio and Tennessee River Valley in the winter.

What are the layers of the Earth's atmosphere?
The atmosphere is divided into five layers. It is thickest near the surface and thins out with height until it eventually merges with space.

Troposphere: The troposphere is the first layer above the surface and contains half of Earth's atmosphere. Weather occurs in this layer.

Stratosphere: The stratosphere is the second layer of the Earth's atmosphere. Many airplanes fly in the stratosphere, because it is very stable. Also, the ozone layer absorbs harmful rays from the Sun.

Mesosphere: The mesosphere is the third layer of the Earth's atmosphere. Meteors or rock fragments burn up in the mesosphere.

Thermosphere: The thermosphere is the fourth layer of the Earth's atmosphere. It's the layer with auroras and where the space shuttle orbits.

Exosphere: The exosphere is the fifth and last layer of the Earth's atmosphere. This is the layer where the atmosphere merges into space. This layer is extremely thin.


What is the tropopause?
The tropopause is the atmospheric boundary located between the troposphere and stratosphere. Going up from the surface, its the point where air ceases to cool with height and becomes almost completely dry.

What is ozone?
Ozone is a natural gas that is found in two different layers of the atmosphere. In the layer around the Earth's surface, otherwise known as the troposphere, bad ozone dirties the air and helps make smog. The troposphere extends up to the stratosphere layer, where good ozone protects life on Earth by absorbing some of the sun's UV rays. Stratospheric ozone is found most often between six to 30 miles above the Earth's surface.

What is the ozone layer?
The ozone layer forms a thin shield high up in the sky and is located in the stratosphere. It protects life on Earth from the sun's ultraviolet rays. In the 1980s, scientists began finding clues that the ozone layer was going away or being depleted. This allows more UV radiation to reach the Earth's surface. This can cause people to have a greater chance of getting too much UV radiation. Too much UV can cause bad health effects like skin cancer, eye damage, and get you sick easier.


What is deforestation?
Deforestation is the cutting down large numbers of trees to use the land for something instead of a forest. Cutting down trees can affect the climate. After rain falls on a forest, mist rises and new rain clouds form. When forests are cut down, this cycle is disrupted, and the area eventually grows drier, causing a change in the local climate. If huge areas of trees are cut down, the carbon dioxide they would have used builds up in the atmosphere and contributes to the greenhouse effect. And without trees to hold the soil and absorb water, rain washes topsoil away, a process called soil erosion.
What is erosion?
Erosion is the wearing away of the land by water, ice or wind. Soil erosion is a natural process. It becomes a problem when human activity causes it to occur much faster than under natural conditions. Wind and water are the main agents of soil erosion.


What is acid rain?
Acid rain is rain, snow or fog that is polluted by acid in the atmosphere and damages the environment. Two common air pollutants acidify rain: sulphur dioxide and nitrogen oxide. When these substances are released into the atmosphere, they can be carried over long distances by prevailing winds before returning to earth as acidic rain, snow, fog or dust. When the environment cannot neutralize the acid being deposited, damage occurs.

Winter Storms

Winter Storms...

How do winter storms form?
Winter storms derive their energy from the clash of two air masses of different temperatures and moisture levels. Winter storms usually form when an air mass of cold, dry, Canadian air moves south and interacts with a warm, moist air mass moving north from the Gulf of Mexico. The point where these two air masses meet is called a front. If cold air advances and pushes away the warm air, it forms a cold front. When warm air advances, it rides up over the denser, cold air mass to form a warm front. If neither air mass advances, it forms a stationary front.


Click Here to see what winter is like where you live.

How is snow formed?
Snow is commonly formed when water vapor undergoes deposition, which is when water vapor changes directly to ice without first becoming a liquid, high in the atmosphere at a temperature of less than 32°F and then falls to the ground.

How do blizzards form?
A blizzard is a long-lasting snowstorm with very strong winds and intense snowfall. You need three things to have a blizzard; cold air at the surface, lots of moisture, and lift. Warm air must rise over cold air.

Blizzards can strand cars on highways for hours or even days. When you are traveling during the winter months, be sure to have an emergency car kit in the vehicle with you.

What are snowflakes?
Snowflakes are made of ice crystals. Each snowflake is six-sided and made of as many as 200 ice crystals. Snowflakes form in clouds where the temperature is below freezing. The ice crystals form around tiny bits of dirt that has been carried up into the atmosphere by the wind. As the snow crystals grow, they become heavier and fall toward the ground.


Why is snow white?
Bright snow blinds us with its gleaming white color because it reflects beams of white light. Instead of absorbing light, snow's complex structure prevents the light from shining through its lattice formation. A beam of white sunlight entering a snow bank is so quickly scattered by a zillion ice crystals and air pockets that most of the light comes bouncing right back out of the snow bank. What little sunlight is absorbed by snow is absorbed equally over the wavelengths of visible light thus giving snow its white appearance. So while many natural objects get their blue, red, and yellow colors from absorbing light, snow is stuck with its white color because it reflects light.


What is sleet?
Sleet is just rain drops that freeze into ice pellets before reaching the ground. Sleet usually bounces when hitting a surface and does not stick to objects. However, it can accumulate like snow and cause a hazard to motorists.

What is freezing rain?
Freezing rain is just rain that falls onto a surface with a temperature below freezing. This causes it to freeze to surfaces, such as trees, cars, and roads, forming a coating or glaze of ice. Even small accumulations of ice can cause a significant hazard.


What is an ice storm?
An ice storm is a type of winter storm caused by freezing rain. The U.S. National Weather Service defines an ice storm as a storm which results in the accumulation of at least 0.25-inch of ice on exposed surfaces.


How do ice storms form?
Ice storms form when a layer of warm air is between two layers of cold air. Frozen precipitation melts while falling into the warm air layer, and then proceeds to refreeze in the cold layer above the ground. This creates freezing rain or a glaze of ice.

What is frost?
Frost is white ice crystals that form on a surface, like the ground or leaves of a plant. Frost is created when the air temperature drops below freezing and the water vapor in the air freezes into ice crystals.

How is lake-effect snow formed?
As the cold air flows over the warm lake water, the relatively warm water heats the air's bottom layer as lake moisture evaporates into the cold air. Since warm air is lighter or less dense than cold air, the heated air rises and begins to cool. As the air cools, the moisture that evaporated into it condenses and forms clouds and snow begins falling from the cloud if the air is humid enough. (Graphic Credit: USA TODAY.)

Cold air moves over warm water and is warmed from below. Moisture evaporates in the air.	Warm moist air rises downwind of lakes and forms heavy snow.

What is a Nor'easter?
Nor'easters can occur in the eastern United States any time between October and April, when moisture and cold air are plentiful. A Nor'easter is named for the winds that blow in from the northeast and drive the storm up the east coast along the Gulf Stream, a band of warm water that lies off the Atlantic coast. They are known for dumping heavy amounts of rain and snow, producing hurricane-force winds, and creating high surfs that cause severe beach erosion and coastal flooding.

What is an Alberta Clipper?
An Alberta clipper is an area of low pressure that generally forms over Alberta, Canada, east of the Rocky Mountains. They develop east of the Rockies because air flowing eastward over the mountains creates favorable conditions. Once an Alberta Clipper forms it usually moves very rapidly to the southeast across the USA's northern Plains and then to the east off the mid-Atlantic Coast. Clippers usually cause only light precipitation with very few producing major snowstorms. However, if conditions are favorable, some Alberta clippers can rapidly intensify off the East Coast once the storm taps the relatively warm moist air over the Atlantic Ocean. The storms that rapidly intensify sometimes spread heavy snow over New England and southeastern Canada. Generally, the main weather features associated with Alberta clippers are some light snow and a reinforcement of cold air over the USA.


What is Wind Chill?
The wind chill is the temperature your body feels when the air temperature is combined with the wind speed. The higher the wind speed the faster exposed areas of your body lose heat and the colder you feel.

Click Here to calculate the Wind Chill.

What is frostbite?
Frostbite is damage to the skin due to prolonged exposure to cold temperatures, usually below 32° F.

What is an avalanche?
An avalanche is a moving mass of snow that may contain ice, soil, rocks, and uprooted trees. The height of a mountain, the steepness of its slope, and the type of snow lying on it all help determine the likelihood of an avalanche. Avalanches begin when an unstable mass of snow breaks away from a mountainside and moves downhill. The growing river of snow picks up speed as it rushes down the mountain. Avalanches have been known to reach speeds of 245 miles an hour (394 kilometers per hour)—about four times as fast as the speediest downhill skier.

Optical Illusions

Optical Illusions...

Why is the sky blue?
The sun shines white and black light to our planet. The white light has all the colors in it. In our upper atmosphere, we have dust particles and oxygen molecules. The white light meaning all of the colors in a rainbow shines through the upper levels of the atmosphere and the blue light scatters across the entire planet. That is why our sky is blue. Now, during sunrise and sunset, the light traveling through atmosphere is longer at the horizon, then if you were to look up high in the sky. There are more dust particles and oxygen molecules at the horizon, so that is why you see such pretty colors like red, oranges and yellows.


How do we get rainbows?
Rainbows are spectacular rays of color. Sunlight looks white, but it's really made up of different colors...red, orange, yellow, green, blue, indigo, and violet. The sun makes rainbows when white sunlight passes through rain drops. The raindrops act like tiny prisms. They bend the different colors in white light, so the light spreads out into a band of colors that can be reflected back to you as a rainbow.


Where do you look for a rainbow?
Three conditions must be met in order for you to see a rainbow. First, it must be raining. Second, the sun must be shining. Third, the observer must be between the sun and the rain. The lower the sun is in the sky, the higher the arc of the rainbow will be.


Can rainbows make a full-circle?
If you could get up high enough in the sky, then you'd see that some rainbows continue below the horizon. That's because when the sun and rain combine to make a rainbow, they really make a full-circle rainbow. We can't see all of the circle, because the horizon blocks it from our view. Pilots high in the sky do sometimes report seeing genuine full-circle rainbows.


Are there double rainbows?
Yes, they do happen! The inner and brighter rainbow has the red on the top and the blue on the bottom side. The outer and dimmer rainbow has the color scheme reversed.


What is an upside-down rainbow?
An upside-down rainbow is an unusual phenomenon caused by sunlight shining through a thin, visible screen of tiny ice crystals high in the sky. Interestingly enough, it has nothing to do with rain. Some people refer to this as a 'smile rainbow'.


Why can't you ever find the end of a rainbow?
A rainbow is an optical illusion, so you just can't catch up to it. When you move, so does it!


Can a rainbow appear during the night?
Yes, they're called moonbows! The nighttime rainbow is very rare and occurs only when the moon is bright enough and positioned properly with respect to falling rain to produce the beautiful effect.


What are the Northern Lights?
The Northern Lights, commonly referred to as the Aurora Borealis, are the result of interactions between the Sun and Earth's outer atmosphere. They are one of the most spectacular light shows to watch as vivid colors glow in the sky. In the Southern Hemisphere, it is called the Aurora Australis.


What causes the auroras?
Most auroras occur in response to energetic particles from a solar storm, which cause the gases of the thin upper atmosphere to glow. They take place at heights between 50 to 100 miles above the Earth. The aurora can last anywhere between a few minutes to several hours. Auroras are most common in polar regions. The various colors, of which green and red predominate, are the results of various light emissions from oxygen and nitrogen gases being energized by the solar particles.

What are crepuscular rays?
Crepuscular rays are are bands of sunlight shining through breaks in clouds on the horizon.


What is a halo?
A halo is a ring around the moon or sun produced by refraction of light through a thin cloud of ice crystals. The halo had red colors on the inside of the ring shifting to blue on the outside.


What are sun dogs?
Sun dogs are bright spots that appear on either side of the sun when there are thin layers of high ice crystal clouds otherwise known as Cirrus clouds. This can also happen at night. These are called moon dogs.


What are sun pillars?
Sun pillars are luminous vertical streaks of light, while or sometimes slightly reddish in color, extending from above and below the sun. They are the result of the light being reflected by the mirror-like surfaces of ice crystals. They are common to see around sunrise and sunset.


What is a blue moon?
The term is used when a full moon occurs twice in the same calendar month. It happens every 2.7 years and never in the month of February because there are not enough days. Is the moon really blue, though? It depends! Most moons are not blue, but if there is a volcanic eruption or even a forest fire, the smoke in the sky can turn the moon a blue color.


What are blue jets?
The blue jet appears as a blue column of light that squirts out the top of a thunderstorm at speeds of 62 miles per second. They sometimes reach a height of 25 to 30 miles. What exactly causes blue jets is not known.


What is a mirage?
A mirage is a refraction phenomena in which the image of some object appears displaced from its true position. A common example of a mirage is the appearance of water some distance down the highway on a hot summer day.


What are sprites?
Sprites are huge blobs of light that occur briefly above thunderstorms. They can extend 55-60 miles high into the ionosphere and can be 100 or more miles wide. Most are invisible to the naked eye on the ground. The best way to see them is from a high-flying aircraft.


What are elves?
Elves are bright flashes of light in the night sky resulting from lightning within thunderstorms. The thin upper atmosphere gives off a brief glow as the electromagnetic pulse from a lightning bolt passes through on its way to outer space. Elves are too fast to be seen with the naked eye, last less than one-thousandth of a second.