​​Welcome To Hannah's Disasters page!Here you will learn about natural disastersAre Humans More Dangerous than Natural Disasters?
Week 2

Natural Disasters

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Volcanic Erruptions
Bush Fire
Meteror shower
Tidle Wave

Limnic eruptions
Week 4How are most natural disasters measerd and who invented it?
The richter scale was named after an Emerican seismologist, named Charles richter.
Natural disasters are measerd by the richter scale (magnitude). Starting with 1 and ending with 10,Each about 60 higher than the last.

external image pH_Color_Chart_Large.jpgWeek 5
external image crossect.gif Earth's crust:The earth's crust or ocean basins has a variable thickness of 35-70km thick on continents or 5-10 on the continents ocean basins.

Mantle:The mantle mainly is composed of ferro-magnesium silicates. It is thought to be 2900 km thick. it is separated into the upper and lower mantle. This where the main part of the earth's heat is located.

Core:The core is part liquid and part solid. The liquid part is the outer core, the inner core is a solid. The outer core is 2300km, the inner core is 1200km.
the outer core is made mainly nickel- iron, while the inner core is made of iron but it is not entirely made of iron. LINK


Hurricanes are giant, spiraling tropical storms that can pack wind speeds of over 160 miles (257 kilometers) an hour and unleash more than 2.4 trillion gallons (9 trillion liters) of rain a day. These same tropical storms are known as cyclones in the northern Indian Ocean and Bay of Bengal, and as typhoons in the western Pacific Ocean.
The Atlantic Ocean’s hurricane season peaks from mid-August to late October and averages five to six hurricanes per year.
Hurricanes begin as tropical disturbances in warm ocean waters with surface temperatures of at least 80 degrees Fahrenheit (26.5 degrees Celsius). These low pressure systems are fed by energy from the warm seas. If a storm achieves wind speeds of 38 miles (61 kilometers) an hour, it becomes known as a tropical depression. A tropical depression becomes a tropical storm, and is given a name, when its sustained wind speeds top 39 miles (63 kilometers) an hour. When a storm’s sustained wind speeds reach 74 miles (119 kilometers) an hour it becomes a hurricane and earns a category rating of 1 to 5 on the Saffir-Simpson scale.
Hurricanes are enormous heat engines that generate energy on a staggering scale. They draw heat from warm, moist ocean air and release it through condensation of water vapor in thunderstorms.
Hurricanes spin around a low-pressure center known as the “eye.” Sinking air makes this 20- to 30-mile-wide (32- to 48-kilometer-wide) area notoriously calm. But the eye is surrounded by a circular “eye wall” that hosts the storm’s strongest winds and rain.
These storms bring destruction ashore in many different ways. When a hurricane makes landfall it often produces a devastating storm surge that can reach 20 feet (6 meters) high and extend nearly 100 miles (161 kilometers). Ninety percent of all hurricane deaths result from storm surges.
A hurricane’s high winds are also destructive and may spawn tornadoes. Torrential rains cause further damage by spawning floods and landslides, which may occur many miles inland.

The best defense against a hurricane is an accurate forecast that gives people time to get out of its way. The National Hurricane Center issues hurricane watches for storms that may endanger communities, and hurricane warnings for storms that will make landfall within 24 hours.

Week6 The atmospheres layers are made up of gases. These gases they are held around earth by gravity. These layers of gases are called the atmosphere. The atmosphere layers protect human and animal life by absorbing the ultraviolet solar radiation. Creating the green house effect.

The Average Temperature Profile of Earth's Atmosphere

Temperature profile of Earth's atmosphere
Temperature profile of Earth's atmosphere

The Troposphere

The troposphere is the lowest layer of the Earth's atmosphere. The air is very well mixed and the temperature decreases with altitude.
Air in the troposphere is heated from the ground up. The surface of the Earth absorbs energy and heats up faster than the air does. The heat is spread through the troposphere because the air is slightly unstable.
Weather occurs in the Earth's troposphere.

The Stratosphere

In the Earth's stratosphere, the temperature increases with altitude. On Earth, ozone causes the increasing temperature in the stratosphere. Ozone is concentrated around an altitude of 25 kilometers. The ozone molecules absorb dangerous kinds of sunlight, which heats the air around them.
The stratosphere is located above the top of the the troposphere.

Ozone - An Overview

The Ozone Hole. Pollution. Skin Cancer. Why does the topic of ozone make the news so much? How important is the ozone in our atmosphere? Why are scientists so concerned about its increase near the surface of the Earth and its disappearance higher up in the atmosphere?
First things first - what is ozone? Ozone is made of three oxygen atoms (O3). The oxygen in our atmosphere that we breathe is made up of two oxygen atoms (O2). When enough ozone molecules are present, it forms a pale blue gas. Ozone has the same chemical structure whether it is found in the stratosphere or the troposphere. Where we find ozone in the atmosphere determines whether we consider it to be "good" or "bad"!
In the troposphere, the ground-level or "bad" ozone is an air pollutant that damages human health, vegetation, and many common materials. It is a key ingredient of urban smog. In the stratosphere, we find the "good" ozone that protects life on Earth from the harmful effects of the Sun's ultraviolet rays. We have good reason to be concerned about the thinning of the ozone layer in the stratosphere. We also have good reason to be concerned about the buildup of ozone in the troposphere. Although simplistic, the saying "Good up high and bad near by," sums up ozone in the atmosphere.

Ozone in the Stratosphere

About 90% of the ozone in the Earth's atmosphere is found in the region called the stratosphere. This is the atmospheric layer between 16 and 48 kilometers (10 and 30 miles) above the Earth's surface. Ozone forms a kind of layer in the stratosphere, where it is more concentrated than anywhere else.
Ozone and oxygen molecules in the stratosphere absorb ultraviolet light from the Sun, providing a shield that prevents this radiation from passing to the Earth's surface. While both oxygen and ozone together absorb 95 to 99.9% of the Sun's ultraviolet radiation, only ozone effectively absorbs the most energetic ultraviolet light, known as UV-C and UV-B. This ultraviolet light can cause biological damage like skin cancer, tissue damage to eyes and plant tissue damage. The protective role of the ozone layer in the upper atmosphere is so vital that scientists believe life on land probably would not have evolved - and could not exist today - without it.
The ozone layer would be quite good at its job of protecting Earth from too much ultraviolet radiation - that is, it would if humans did not contribute to the process. It's now known that ozone is destroyed in the stratosphere and that some human-released chemicals such as CFC’s are speeding up the breakdown of ozone, so that there are "holes" now in our protective shield.
While the stratospheric ozone issue is a serious one, in many ways it can be thought of as an environmental success story. Scientists detected the developing problem, and collected the evidence that convinced governments around the world to take action. Although the elimination of ozone-depleting chemicals from the atmosphere will take decades yet, we have made a strong and positive beginning. For the first time in our species' history, we have tackled a global environmental issue on a global scale.

The Mesosphere

In the Earth's mesosphere, the air is relatively mixed together and the temperature decreases with altitude. The atmosphere reaches its coldest temperature of around -90°C in the mesosphere. This is also the layer in which a lot of meteors burn up while entering the Earth's atmosphere.
The mesosphere is on top of the stratosphere The upper parts of the atmosphere, such as the mesosphere, can sometimes be seen by looking at the very edge of a planet.

The Thermosphere

The thermosphere is the fourth layer of the Earth's atmosphere and is located above the mesosphere. The air is really thin in the thermosphere. A small change in energy can cause a large change in temperature. That's why the temperature is very sensitive to solar activity. When the sun is active, the thermosphere can heat up to 1,500° C or higher!
The Earth's thermosphere also includes the region of the atmosphere called the ionosphere. The ionosphere is a region of the atmosphere that is filled with charged particles. The high temperatures in the thermosphere can cause molecules to ionize. This is why an ionosphere and thermosphere can overlap.

The Ionosphere

Scientists call the ionosphere an extension of the thermosphere. So technically, the ionosphere is not another atmospheric layer. The ionosphere represents less than 0.1% of the total mass of the Earth's atmosphere. Even though it is such a small part, it is extremely important!
The upper atmosphere is ionized by solar radiation. That means the Sun's energy is so strong at this level, that it breaks apart molecules. So there ends up being electrons floating around and molecules which have lost or gained electrons. When the Sun is active, more and more ionization happens!
Different regions of the ionosphere make long distance radio communication possible by reflecting the radio waves back to Earth. It is also home to auroras.
Temperatures in the ionosphere just keep getting hotter as you go up!

Regions of the Ionosphere

The ionosphere is broken down into the D, E and F regions. The breakdown is based on what wavelength of solar radiation is absorbed in that region most frequently.
The D region is the lowest in altitude, though it absorbs the most energetic radiation, hard x-rays. The D region doesn't have a definite starting and stopping point, but includes the ionization that occurs below about 90km.
The E region peaks at about 105km. It absorbs soft x-rays.
The F region starts around 105km and has a maximum around 600km. It is the highest of all of the regions. Extreme ultra-violet radiation (EUV) is absorbed there.
On a more practical note, the D and E regions reflect AM radio waves back to Earth. Radio waves with shorter lengths are reflected by the F region. Visible light, television and FM wavelengths are all too short to be reflected by the ionosphere. So your t.v. stations are made possible by satellite transmissions.
Layers of Earth's ionosphere
Layers of Earth's ionosphere

This image shows how the ionosphere is divided even further into layers: D, E, and F layers.

The Sun's Effect on the Ionosphere

Invisible layers of ions and electrons are found in the Earth's atmosphere. We call this region of atmosphere the ionosphere.
The main source of these layers is the Sun's ultraviolet light which ionizes atoms and molecules in the Earth's upper atmosphere. During this process, electrons are knocked free from molecules or particles in the atmosphere.
Flares and other big events on the Sun produce increased ultraviolet, x-ray and gamma-ray photons that arrive at the Earth just 8 minutes later (other particles from the Sun may arrive days later) and dramatically increase the ionization that happens in the atmosphere. So, the more active the Sun, the thicker the ionosphere!
Penetration of Earth's atmosphere by solar radiation
Penetration of Earth's atmosphere by solar radiation
This image shows how different types of solar radiation (x-rays to infrared radiation) penetrate into the Earth's atmosphere. It is this solar radiation that ionizes the upper atmosphere, creating the ionosphere.

The Exosphere

Very high up, the Earth's atmosphere becomes very thin. The region where atoms and molecules escape into space is referred to as the exosphere. The exosphere is on top of the thermosphere.

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The Earth
Earth, which is our base from which we look into space, is constantly moving. Understanding this movement is one of the most useful and important things in astronomy.
The earth orbits the sun in an elliptical orbit and the moon orbits the earth with the same kind of orbit. Looking down from the north pole, the earth spins in a counterclockwise direction on an imaginary line called its axis once every day. This accounts for the fact that the sun rises in the east and sets in the west. The earth’s axis is tilted with respect to the plane of its orbit at an angle of about 23.4 degrees. If we position ourselves high above the north pole, we would see that the earth orbits the sun in a counterclockwise motion, coming to the same position among the stars every 365.26 earth days. We would also see that the moon also orbits the earth in a counterclockwise motion. This is illustrated in the following example.
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Figure 1: The directions of the orbits of the earth and moon.
The average distance from the earth to the sun, the semimajor axis of its orbit, is 149,597,890 km. This distance was not known until recently and it is called the astronomical unit or AU. The distances of the other planets to the sun are usually measured in astronomical units.
Because of the tilt of the earth, not every place on earth gets light every day. Also, some places have extremely short days.
As the earth revolves around the sun, the place where light shines the brightest changes. This motion gives us the different seasons. For instance, the poles receive less light than does the equator because of the angle that the land around the poles receive the sun’s light. When the north pole is tilted toward the sun, the northern hemisphere is presented to the sun at a greater angle than the southern hemisphere and the northern hemisphere gets warmer. When this happens, the northern hemisphere gets summer while the southern hemisphere gets winter. When the south pole is tilted toward the sun, the two seasons reverse hemispheres. This is illustrated in the following image.
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Figure 2: The positions of earth at the different seasons. Counterclockwise from lower left: summer, fall, winter, spring (northern hemisphere).
The earth’s orbit is called the ecliptic. The plane which contains the ecliptic is the reference plane for the positions of most solar system bodies. Viewed from earth, the ecliptic is the apparent motion of the sun among the stars.
The earth’s equator is a circle going around the earth which is on a plane that is perpendicular to the earth’s axis. The equator and the plane on which it lies are illustrated in the following image.
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Figure 3: The equatorial plane.
The Equinoxes
This equatorial plane is one of the most important in astronomy because it intersects the plane of the ecliptic and gives us a reference point in space by which we can measure the positions of stars. This plane also divides the earth into halves, the northern half being the northern hemisphere, the other half being the southern hemisphere. The intersection of these planes is a line, which for convenience we will call the line of equinoxes. The real definition of equinox is the point on the celestial sphere which intersects this line, but since the celestial sphere is an imaginary sphere with any size, the equinoxes are really lines. Also, for some purposes and illustrations, it is more convenient to think of the equinoxes as a line extending into space. For other purposes, it is convinient to think of the equinoxes as directions. The two planes are illustrated below.
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Figure 4: The vernal equinox from two perspectives.
One half of this line is called the vernal equinox; the other half is called the autumnal equinox. At two points in the earth’s orbit this line intersects the sun. These two places mark the start of two of the four seasons, autumn or spring. The autumnal equinox starts autumn around September 23. From earth, this marks the time when the sun looks as if it is crossing the plane of the equator on its way south. The vernal equinox starts spring around March 21. This marks the time when the sun looks as if it is crossing the plane of the equator on its way north. The earth carries the plane of the equator along with it. When the sun looks as if it is on its way north or south, the earth is actually carrying the equatorial plane along so that it crosses the sun.
Perpendicular to this line of equinoxes is a line which contains the solstices. The solstices are points on the ecliptic which start the other two seasons, summer and winter, when they cross the sun. The summer solstice is one half of this line, the winter solstice is the other half of this line. The half of this line that is north of the celestial equator is the summer solstice, the half that is south of the celestial equator is the winter solstice. Currently, the winter solstice starts winter for the northern hemisphere at about the time the earth is closest to the sun. This line is illustrated in the following example.
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Figure 5: The summer and winter solstices.
Because of centrifugal force involved when an object spins, the earth is not a perfect sphere, but is somewhat flattened at the poles and bulges out at the equator. The distance from any point on the equator to the center of the earth is longer than the distance from either pole to the center of the earth. This is illustrated in the following image which is exaggerated for clarity. The form caused by this equatorial bulge is called a geoid.
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Figure 6: A geoid.
The Moon
The moon is the earth’s only natural satellite. Its average distance from the earth is 384,403 km. Its revolution period around the earth is the same length and direction as its rotation period, which results in the moon always keeping one side turned toward the earth and the other side turned away from the earth. This type of motion is called synchronous rotation. The side turned away from the earth is called the moon’s dark side, even though it is lit half of the time. The moon’s sidereal period of revolution is about 27.32 days long. This means that a line drawn through the center of the earth and the moon would point to the same star every 27.32 days. Due to slight variations in the orbital velocity of the moon, over a 30 year period, 59% of the moon’s surface is made visible. This is known as libration.
The moon’s orbit is not in the plane of the ecliptic and because of the elliptical nature of the moon’s orbit, it is not always the same distance from the earth. At the two intersections of the moon’s orbit and the plane of the ecliptic are two nodes. These nodes regress along the plane of the ecliptic, making one complete rotation every 18.61 years. See Orbits.
The Effect of the Moon
The moon has a noticeable effect on the earth in the form of tides, but it also affects the motion and orbit of the earth. The moon does not orbit the center of the earth, rather, they both revolve around the center of their masses called the barycenter. This is illustrated in the following animation.
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Figure 7: The earth and moon revolving around the barycenter. Notice how the earth moves slightly.
The sun acts on the earth and its moon as one entity with its center at the barycenter. Since the earth revolves around the barycenter, which in turn orbits the sun, the earth follows a wobbly path around the sun. This is illustrated in the following example. To complicate things further, the barycenter is not always in the same place due to the elliptical nature of the moon’s orbit.
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Figure 8: The wobble of the earth's orbit.
*Image illustrative only; number of intersections is greater.

The sun attracts the moon in such a way that it perturbs its orbit every 31.807 days, this phenomenon is called evection. The moon also changes the position of the earth’s equinoxes. The sun and moon each attract the earth’s equatorial bulge, trying to bring it into alignment with themselves. This torque is counteracted by the rotation of the earth. The combination of these two forces is a slow rotation of the earth’s axis, which in turn results in a slow westward rotation of the equinoxes. Looking down from the north pole, the equinoxes would appear to be rotating in a clockwise motion. The equinoxes and poles complete a rotation every 25,800 years. The equinoxes move at a rate of about 50.27 arc seconds per year. This phenomenon in known as the precession of the equinoxes and is illustrated in the following image.
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Figure 9: The precession of the equinoxes. The blue disk is the equatorial plane. The white line is the equinoxes. The green plane is the plane of the ecliptic.
The north pole is currently pointing to a spot near the star Polaris. Because the vernal equinox is the starting point for most star charts, the charts must be made for a certain period. The star charts must be updated periodically to account for this movement of the reference point.
Because of the seasonal changes in the ice, snow, atmospheric distribution, and perhaps because of movements in the material within the earth, the geographic poles constantly change position in relation to the earth’s surface. This phenomenon is known as the Chandler wobble. Scientists have resolved the change into two almost circular components, the first with a radius of about 6 meters and a period of 12 months, the second with a radius of 3-15 meters and a period of about 14 months.
The sun and moon, because of their varying distances and directions in relation to the earth, constantly vary their gravitational attractions on the earth. This makes the poles wander irregularly by about + or - 9 arc seconds from its average, or mean, position. This phenomenon is known as nutation and has a period of about 18.6 years. The primary component of this is from the moon and is known as lunar nutation.
The sun and moon also constantly change the earth’s rate of spin.
Star charts use the mean equinox instead of the true equinox for their zero points. The mean equinox is the position of the equinox corrected for the slight but noticeable changes caused by nutation and the Chandler wobble. The mean equinox is still affected by precession, however, and does change position, but does it at a constant, predictable rate. Scientists requiring up-to-date precision information about the position of the earth can use the International Earth Rotation Service or IERS. This information can be found at the IERS web site at http://maia.usno.navy.mil/
The Sun
Because of the elliptical nature of the earth’s orbit and constant changes in the earth’s rate of spin because of the previously mentioned phenomena, the sun, as seen from earth, is moving at a non-uniform rate. This makes it difficult to use the real position of the sun as a reference for time keeping. For these purposes, a point which moves at a constant rate around the earth is used instead of the real position of the sun. This point is c http://www.youtube.com/watch?v=0-6RvYyFoTs