The climatic effects of water vapour

This article is a couple of years old but it is excellent. I have been meaning to write about it for some time but there have been recent discussions on the web regarding the thermodynamic tendencies of the entire planet, as it relates to space and the sun with comparisons to the Moon, Venus and Mars.  While these discussions are scientifically interesting, they do not really address the issue at hand.

There are articles and bloggers out there that are saying that we are in steady state due to the thermodynamics of the two bodies and that we cannot get appreciably warmer or colder. I have yet to see a mathematical proof of these claims that proves the points and don’t buy into their logic. There is no question that the planet can get warmer or colder - look at the differences in temperature between Boston and Miami!  Since most of the people that contributed to the IPCC report are calling for an increase of 3-6 deg C, this is similar to the difference in temperature that you could experience by driving south a couple hundred miles.  Also remember that when we talk about thermodynamics, we really need to talk in absolute degrees using the Kelvin scale and at that point we are discussing a 1% temperature change predicted by IPCC.

The real issue to understand is how much energy can the existing greenhouse gases absorb and how much would they absorb if CO2, methane, and others changed their concentrations. There are a variety of articles to read on this subject but since we need to have some understanding of chemistry and quantum physics to really dig into this subject, this article is a good overview. I am trying to simplify the conversation by my quotes below.  Click through and read the article to get a better understanding.  If you really want to dig, start googling.

Of significant note (and probably my other reason for choosing this article) is that the author repeatedly refers to the inaccuracies of the climate models and that they need to do a better job. If you have read much of my site, you will know that this is a favorite topic of mine. We need better models!

Extreme variations in local weather and the seasons make it easy for people to mutter “greenhouse effect”, and blame everything on carbon dioxide. Along with other man-made gases, such as methane, carbon dioxide has received a bad press for many years and is uniformly cited as the major cause of the greenhouse effect. This is simply not correct. While increases in carbon dioxide may be the source of an enhanced greenhouse effect, and therefore global warming, the role of the most vital molecule in our atmosphere - water - is rarely discussed.

---

Many aspects of the seemingly simple water molecule conspire to make it difficult to model its effect on our climate. Unlike most other atmospheric gases, the distribution of water in the atmosphere varies strongly with time, location and altitude. Water is also unique among atmospheric molecules because it changes phase at terrestrial temperatures.

---

The atmosphere plays a crucial role in the Earth’s radiation budget because it absorbs both the incoming radiation from the Sun and the outgoing radiation that is reflected from the planet’s surface. However, the radiation in each of these processes has very different wavelengths. The Sun radiates approximately as a black body with a temperature of 5800 K, which peaks in the optical region at a wavelength of about 0.6 µm. The reflected radiation profile, on the other hand, is much closer to a black body at a temperature of 275 K, and has a peak at much longer infrared wavelengths (about 11 µm).

---

The greenhouse effect is precisely the difference between the long-wave radiation that is emitted by the Earth’s surface and the upward thermal radiation that leaves the tropopause - the upper boundary of the turbulent portion of the atmosphere that we all inhabit. The greenhouse effect is about 146 W m-2 in clear skies and some 30 W m-2 higher under cloud cover.

---

For clear skies, the models predict that the atmosphere absorbs much less sunlight than is measured by a variety of satellite and aircraft. The difference between the predictions and the measurements can be as large as 30 W m-2. (see “Radiation budget is called to account” by A Maurellis Physics World November 2001 pp22-23). This problem has become known as the absorption anomaly. And there are even worse problems in understanding absorption models when the sky is cloudy.

---

Not all models underestimate the amount of atmospheric absorption because some physicists choose to add extra absorption to their models to mop up the surplus radiation.

---

Molecules absorb radiation at characteristic wavelengths that excite one or more of their rotational, vibrational or electronic degrees of freedom.

---

More importantly for climatic issues, the vibrational degrees of freedom in water, ozone and carbon-dioxide molecules can absorb light in the infrared region. In the case of carbon dioxide it is these vibrations that break the symmetry of the molecule and enable it to become excited by atmospheric radiation.

---

Furthermore, the vibrational motions of water have a large amplitude because hydrogen atoms are very light. As a result, water does not vibrate as a simple harmonic oscillator - as most molecules do - and its vibrational transitions do not obey the general harmonic-selection rule. The only transitions allowed by this rule are those in which a vibrational quantum number changes by a single quantum. For water, transitions that involve changes of up to eight vibrational quanta are atmospherically important, which means that the water-vapour spectrum covers a large range of wavelengths and line intensities, and is generally very complex.

---

Experiments that were performed by Roland Schermaul and the late Richard Learner at Imperial College in London in 2001 have cast previous measurements of the absorption spectrum of water into considerable doubt. … They found that the strong spectral lines absorbed significantly more light - between 5% and 25% - than previous laboratory measurements had suggested.

---

…water turns out to be responsible for about 60% of the greenhouse effect, while the much-reviled carbon-dioxide molecule accounts for just 26%. Ozone accounts for 8%, and methane and nitrous oxide - the atmospheric concentrations of which have been increased by human activity - contribute a further 8% to the greenhouse effect.

---

It turns out that typical abundances of carbon dioxide are sufficient to make most of its absorption bands relatively opaque (see figure 3). Because the strong absorption bands are saturated, adding more carbon dioxide to the atmosphere increases its absorptions logarithmically rather than linearly….

---

We have tried to outline some of the unresolved issues concerning water in the atmosphere. But there are others.

---

Another problem is that there are few data that tell us about the amount of water vapour in the atmosphere over history, which makes it difficult to determine the climatic effects from long-term changes in the atmosphere’s water-vapour content.

---

A complete solution to the various problems that are associated with water absorption can only be obtained by constructing an accurate and comprehensive theoretical model of the spectrum of water.

---

It is clear that the absorption of radiation by water vapour determines many characteristics of our atmosphere. While we would not try to provoke any worldwide movement that was aimed at suppressing water emissions, it would seem that the climatic role of water does not receive the general attention it deserves.

I probably have not done total justice by my above edits. You will learn a great deal more by clicking through to the original article here.

Did you know that you can have these articles emailed to you? Click on the “Subscribe to email” link in the upper right corner, fill out the details, and you are set. No one will see your email address and you won’t get more spam by doing this.

source:http://globalwarming-factorfiction.com 

Global Warming Basics

What causes global warming?
Carbon dioxide and other air pollution that is collecting in the atmosphere like a thickening blanket, trapping the sun’s heat and causing the planet to warm up. Coal-burning power plants are the largest U.S. source of carbon dioxide pollution — they produce 2.5 billion tons every year. Automobiles, the second largest source, create nearly 1.5 billion tons of CO2 annually.Here’s the good news: technologies exist today to make cars that run cleaner and burn less gas, modernize power plants and generate electricity from nonpolluting sources, and cut our electricity use through energy efficiency. The challenge is to be sure these solutions are put to use.
Is the earth really getting hotter?
Yes. Although local temperatures fluctuate naturally, over the past 50 years the average global temperature has increased at the fastest rate in recorded history. And experts think the trend is accelerating: the 10 hottest years on record have all occurred since 1990. Scientists say that unless we curb global warming emissions, average U.S. temperatures could be 3 to 9 degrees higher by the end of the century.
Are warmer temperatures causing bad things to happen?
Global warming is already causing damage in many parts of the United States. In 2002, Colorado, Arizona and Oregon endured their worst wildfire seasons ever. The same year, drought created severe dust storms in Montana, Colorado and Kansas, and floods caused hundreds of millions of dollars in damage in Texas, Montana and North Dakota. Since the early 1950s, snow accumulation has declined 60 percent and winter seasons have shortened in some areas of the Cascade Range in Oregon and Washington.Of course, the impacts of global warming are not limited to the United States. In 2003, extreme heat waves caused more than 20,000 deaths in Europe and more than 1,500 deaths in India. And in what scientists regard as an alarming sign of events to come, the area of the Arctic’s perennial polar ice cap is declining at the rate of 9 percent per decade.
Is global warming making hurricanes worse?
Global warming doesn’t create hurricanes, but it does make them stronger and more dangerous. Because the ocean is getting warmer, tropical storms can pick up more energy and become more powerful. So global warming could turn, say, a category 3 storm into a much more dangerous category 4 storm. In fact, scientists have found that the destructive potential of hurricanes has greatly increased along with ocean temperature over the past 35 years.
Is there really cause for serious concern?
Yes. Global warming is a complex phenomenon, and its full-scale impacts are hard to predict far in advance. But each year scientists learn more about how global warming is affecting the planet, and many agree that certain consequences are likely to occur if current trends continue. Among these:
Melting glaciers, early snowmelt and severe droughts will cause more dramatic water shortages in the American West.
Rising sea levels will lead to coastal flooding on the Eastern seaboard, in Florida, and in other areas, such as the Gulf of Mexico.
Warmer sea surface temperatures will fuel more intense hurricanes in the southeastern Atlantic and Gulf coasts.
Forests, farms and cities will face troublesome new pests and more mosquito-borne diseases.
Disruption of habitats such as coral reefs and alpine meadows could drive many plant and animal species to extinction.
Could global warming trigger a sudden catastrophe?
Recently, researchers — and even the U.S. Defense Department — have investigated the possibility of abrupt climate change, in which gradual global warming triggers a sudden shift in the earth’s climate, causing parts of the world to dramatically heat up or cool down in the span of a few years.In February 2004, consultants to the Pentagon released a report laying out the possible impacts of abrupt climate change on national security. In a worst-case scenario, the study concluded, global warming could make large areas of the world uninhabitable and cause massive food and water shortages, sparking widespread migrations and war.While this prospect remains highly speculative, many of global warming’s effects are already being observed — and felt. And the idea that such extreme change is possible underscores the urgent need to start cutting global warming pollution.
What country is the largest source of global warming pollution?
The United States. Though Americans make up just 4 percent of the world’s population, we produce 25 percent of the carbon dioxide pollution from fossil-fuel burning — by far the largest share of any country. In fact, the United States emits more carbon dioxide than China, India and Japan, combined. Clearly America ought to take a leadership role in solving the problem. And as the world’s top developer of new technologies, we are well positioned to do so — we already have the know-how.
How can we cut global warming pollution?
It’s simple: By reducing pollution from vehicles and power plants. Right away, we should put existing technologies for building cleaner cars and more modern electricity generators into widespread use. We can increase our reliance on renewable energy sources such as wind, sun and geothermal. And we can manufacture more efficient appliances and conserve energy.
Why aren’t these technologies more commonplace now?
Because, while the technologies exist, the corporate and political will to put them into widespread use does not. Many companies in the automobile and energy industries put pressure on the White House and Congress to halt or delay new laws or regulations — or even to stop enforcing existing rules — that would drive such changes. From requiring catalytic converters to improving gas mileage, car companies have fought even the smallest measure to protect public health and the environment. If progress is to be made, the American people will have to demand it.
Do we need new laws requiring industry to cut emissions of global warming pollution?
Yes. The Bush administration has supported only voluntary reduction programs, but these have failed to stop the growth of emissions. Even leaders of major corporations, including companies such as DuPont, Alcoa and General Electric, agree that it’s time for the federal government to create strong laws to cut global warming pollution. Public and political support for solutions has never been stronger. Congress is now considering fresh proposals to cap emissions of carbon dioxide and other heat-trapping pollutants from America’s largest sources — power plants, industrial facilities and transportation fuels.Stricter efficiency requirements for electric appliances will also help reduce pollution. One example is the 30 percent tighter standard now in place for home central air conditioners and heat pumps, a Clinton-era achievement that will prevent the emission of 51 million metric tons of carbon — the equivalent of taking 34 million cars off the road for one year. The new rule survived a Bush administration effort to weaken it when, in January 2004, a federal court sided with an NRDC-led coalition and reversed the administration’s rollback.
Is it possible to cut power plant pollution and still have enough electricity?
Yes. First, we must use more efficient appliances and equipment in our homes and offices to reduce our electricity needs. We can also phase out the decades-old, coal-burning power plants that generate most of our electricity and replace them with cleaner plants. And we can increase our use of renewable energy sources such as wind and sun. Some states are moving in this direction: California has required its largest utilities to get 20 percent of their electricity from renewable sources by 2017, and New York has pledged to compel power companies to provide 25 percent of the state’s electricity from renewable sources by 2013.
How can we cut car pollution?
Cost-effective technologies to reduce global warming pollution from cars and light trucks of all sizes are available now. There is no reason to wait and hope that hydrogen fuel cell vehicles will solve the problem in the future. Hybrid gas-electric engines can cut global warming pollution by one-third or more today; hybrid sedans, SUVs and trucks from several automakers are already on the market.But automakers should be doing a lot more: They’ve used a legal loophole to make SUVs far less fuel efficient than they could be; the popularity of these vehicles has generated a 20 percent increase in transportation-related carbon dioxide pollution since the early 1990s. Closing this loophole and requiring SUVs, minivans and pick-up trucks to be as efficient as cars would cut 120 million tons of carbon dioxide pollution a year by 2010. If automakers used the technology they have right now to raise fuel economy standards for new cars and light trucks to a combined 40 m.p.g., carbon dioxide pollution would eventually drop by more than 650 million tons per year as these vehicles replaced older models.For more information on hybrid vehicles, see NRDC’s hybrid guide.
Ways To Reduce Global Warming
There are many simple steps one can take right now to cut global warming pollution. Make conserving energy a part of your daily routine. Each time one choose a compact fluorescent light bulb over an incandescent bulb, for example, you’ll lower your energy bill and keep nearly 700 pounds of carbon dioxide out of the air over the bulb’s lifetime. By opting for a refrigerator with the Energy Star label — indicating it uses at least 15 percent less energy than the federal requirement — over a less energy-efficient model, one can reduce carbon dioxide pollution by nearly a ton in total. Join NRDC in campaign against global warming.

source 

Water Cycle

The Earth’s water is always in circulation. It has been recycled for the last 3 billion years. This process is called the water cycle.

The cycle starts when the sun’s heat evaporates water from the oceans into the atmosphere to form clouds. When the conditions are just right, the clouds release water as rain or snow. Most of the rain falls in the oceans, but the rest falls onto land. Rivers and streams collect water from the ground and return it to the ocean so the whole cycle can start all over again. The water cycle never ends because the salty ocean water constantly supplies fresh water to the continents

One process which tranfers water from the ground back to the atmosphere is evaporation. Evaporation is when water passes from a liquid phase to a gas phase. Rates of evaporation of water depend on things like the temperature, humidity, and wind.

Water that is held in lakes and rivers evaporates directly into the atmosphere. Some of the water in the ground may also be returned to the atmosphere by way of evaporation through the soil surface. Of course, the ocean is the greatest source for water evaporated into the atmosphere.Transpiration is the process by which plants return water to the atmosphere. After absorbing water from the ground, plants release water through their leaves. Transpiration helps plants stay cool, in the same way perspiration keeps humans and animals cool.

source: http://www.windows.ucar.edu

Currents of the Ocean

This illustration shows the circulation of the ocean’s surface water. Names of the major ocean currents are noted. Warm currents are noted in the color red and cold currents are noted in the color blue. Click on image for full size (260K JPEG) Windows Original

There are two main sections of ocean water: the surface layer and the the deep waters. The surface layer is the layer at the top of the ocean that is well mixed by waves, tides, and weather events like rain or a hurricane. The surface layer sits on top of the deep water because the surface layer is less dense. The depth of the surface layer varies depending on location and season, but the depth is typically a couple hundred meters. There is a boundary layer between the surface layer and the deep waters that is called the the pycnocline (meaning rapid change of density). The pycnocline is caused by rapid changes of temperature and salinity.Surface water movement takes place in the form of currents. Currents move ocean water horizontally at the ocean’s surface. Surface currents are driven mainly by the wind. Other forces such as the Coriolis effect and the location of land masses do affect surface current patterns. In fact, huge circular patterns called current gyres can be seen when looking at the world’s ocean currents. From the equator to middle latitudes, the circular motion is clockwise in the Northern Hemisphere and counterclockwise in the Southern hemisphere. Near the poles of the Earth, there is a tendency for the gyres to flow in the opposite direction. This circulation of water helps spread energy from the Sun. The Sun warms water at the equator and then water and heat are transported to higher latitudes.

Major ocean currents of the world include (please see illustration for a more complete listing):

• North & South Equatorial Current
• Equatorial Counter Current
• North Atlantic Drift
• Gulf Stream
• Kuroshio Current (off of Japan)
• Antarctic Circumpolar Current
• East Australian current

source:http://www.windows.ucar.edu

Historical Data on Global Warming

Historical Data on Global Warming
provided by U.S. Government Agencies

By Dan Pangburn, P.E.

I have been researching the global warming issue for months. I am a licensed Mechanical Engineer with an MSc in Mechanical Engineering. The following is a brief verbal description of some of my sources and findings with graphics that show these findings.

Climate obviously has changed and will continue to change. But the observation that ice is melting, which can look dramatic on TV, does not show that human activity is the cause. The assertion that humans have or ever can have a significant influence on climate such as by limiting the use of fossil fuel (a.k.a. limiting human production of carbon dioxide) is not supported by any historical record. Avoid the group-think ‘consensus science’ and de facto censorship by Climate Scientists. Directly interrogate official government data that taxpayers have paid for from ORNL and NOAA as follows:

The temperature¹ has varied substantially while the carbon dioxide in the atmosphere² exhibits a smooth progressive rise. Note on this graph that prior to about 1910, and again from 1944 to about 1976, temperature showed a decreasing trend while atmospheric carbon dioxide level was increasing. Thus, as shown on this graph, until 1998 the average global temperature trend and atmospheric carbon dioxide level went in the same direction about half the time and in opposite directions the other half. The temperature rise that received so much attention and contributed to the Global Warming mistake lasted for about 22 years from 1976 to 1998. The temperature stopped significant increase in 1998. According to NOAA data, the average global temperature trended down during 2007 to lower than it was in 1998. This down-trend continues with the average for the first two months of 2008 being substantially lower.

full story

The Physical Ocean

Physical oceanography is the study of the physical properties and dynamic processes of the oceans. Physical oceanographers study the interaction of the ocean with the atmosphere, how the ocean stores and releases heat, the physical properties (or chemical content) of water throughout the ocean, and the formation and movement of currents and coastal dynamics. In order to understand these phenomena, researchers at NASA measure ocean surface topography, sea surface temperature, the speed and direction of the winds over the ocean, and soon, sea surface salinity (salt content). From these data, scientists can further study ocean currents, and sea ice.

Satellites provide a double advantage over traditional ship-based measuring systems as they are able to provide continuous measurements on a global scale. A single global snapshot - which would be expensive and time-consuming, but possible from ships or buoys - fails to convey how the physical state of the ocean is changing. With satellite data, scientists can understand not only how the ocean behaves at a given point in time, but also how the ocean changes and fluctuates. For example the patterns of heat distribution within the ocean and the geographic extent of current systems affect climate and weather. A displacement of weather patterns can extend summer weather or lead to droughts or floods.

Learn more about physical oceanography by following the links below:

The Physical Ocean
	Ocean Surface Topography NASA uses extremely precise measurements of the height of the ocean acquired from orbiting satellite instruments to map the topography of the ocean surface. Ocean Surface Topography (OST) data contains information that has practical applications in such areas as the study of worldwide weather and climate patterns, the monitoring of sea level evolution, and the protection of our ocean fisheries. [+ more ]
	Sea Surface Temperature Instruments aboard NASA satellites use their vantage point from space to collect global measurements of the ocean’s surface temperature. By developing global, detailed, and decades-long views of Sea Surface Temperature (SST), data obtained from NASA satellites provide the basis for prediction of climate change, ocean currents, and global climate patterns like the potent El Niño-La Niña cycles. [+ more ]
	Sea Surface Winds Winds are the largest source of momentum for the ocean surface. Winds have an impact on both individual currents and complete current systems. When observing ocean phenomenon, it is critical to consider winds as part of what we measure. [+ more ]
	Sea Surface Salinity Sea Surface Salinity (SSS) tells us the about the concentration of dissolved salts in the upper centimeter of the ocean surface. Even small variations in SSS can have dramatic effects on the water cycle and ocean circulation. [+ more ]
	Ocean Surface Currents The ocean is constantly in motion, with currents that travel both on the surface and in the depths. These movements carry water vast distances. Only from space can the true extent of currents be tracked in real time. NASA satellites employ a variety of instruments to interpret ocean currents. [+ more ]
	Sea Ice Sea ice is formed when ocean water is cooled below its freezing temperature. Sea ice is important to the study of oceans because it impacts oceanic chemical and physical properties, density structure, oceanic dynamics, and exchanges between the ocean and the atmosphere. A variety of NASA instruments are used to measure and study sea ice from space. [+ more]

source:http://science.hq.nasa.gov/ocean

Earthquake:Overview

Earthquake is a shaking of the ground caused by the sudden breaking and shifting of large sections of Earth’s rocky outer shell. Earthquakes are among the most powerful events on earth, and their results can be terrifying. A severe earthquake may release energy 10,000 times as great as that of the first atomic bomb. Rock movements during an earthquake can make rivers change their course. Earthquakes can trigger landslides that cause great damage and loss of life. Large earthquakes beneath the ocean can create a series of huge, destructive waves called tsunamis (tsoo NAH meez)that flood coasts for many miles.Earthquakes almost never kill people directly. Instead, many deaths and injuries result from falling objects and the collapse of buildings, bridges, and other structures. Fire resulting from broken gas or power lines is another major danger during a quake. Spills of hazardous chemicals are also a concern during an earthquake.

The force of an earthquake depends on how much rock breaks and how far it shifts. Powerful earthquakes can shake firm ground violently for great distances. During minor earthquakes, the vibration may be no greater than the vibration caused by a passing truck.

On average, a powerful earthquake occurs less than once every two years. At least 40 moderate earthquakes cause damage somewhere in the world each year. Scientists estimate that more than 8,000 minor earthquakes occur each day without causing any damage. Of those, only about 1,100 are strong enough to be felt.

This article discusses Earthquake (How an earthquake begins) (How an earthquake spreads) (Damage by earthquakes) (Where and why earthquakes occur) (Studying earthquakes).

How an earthquake begins

Most earthquakes occur along a fault — a fracture in Earth’s rocky outer shell where sections of rock repeatedly slide past each other. Faults occur in weak areas of Earth’s rock. Most faults lie beneath the surface of Earth, but some, like the San Andreas Fault in California, are visible on the surface. Stresses in Earth cause large blocks of rock along a fault to strain, or bend. When the stress on the rock becomes great enough, the rock breaks and snaps into a new position, causing the shaking of an earthquake.

Earthquakes usually begin deep in the ground. The point in Earth where the rocks first break is called the focus, also known as the hypocenter, of the quake. The focus of most earthquakes lies less than 45 miles (72 kilometers) beneath the surface, though the deepest known focuses have been nearly 450 miles (700 kilometers) below the surface. The point on the surface of Earth directly above the focus is known as the epicenter of the quake. The strongest shaking is usually felt near the epicenter.

From the focus, the break travels like a spreading crack along the fault. The speed at which the fracture spreads depends on the type of rock. It may average about 2 miles (3.2 kilometers) per second in granite or other strong rock. At that rate, a fracture may spread more than 350 miles (560 kilometers) in one direction in less than three minutes. As the fracture extends along the fault, blocks of rock on one side of the fault may drop down below the rock on the other side, move up and over the other side, or slide forward past the other.

How an earthquake spreads

When an earthquake occurs, the violent breaking of rock releases energy that travels through Earth in the form of vibrations called seismic waves. Seismic waves move out from the focus of an earthquake in all directions. As the waves travel away from the focus, they grow gradually weaker. For this reason, the ground generally shakes less farther away from the focus.

There are two chief kinds of seismic waves: (1) body waves and (2) surface waves. Body waves, the fastest seismic waves, move through Earth. Slower surface waves travel along the surface of Earth.

Body waves tend to cause the most earthquake damage. There are two kinds of body waves: (1) compressional waves and (2) shear waves. As the waves pass through Earth, they cause particles of rock to move in different ways. Compressional waves push and pull the rock. They cause buildings and other structures to contract and expand. Shear waves make rocks move from side to side, and buildings shake. Compressional waves can travel through solids, liquids, or gases, but shear waves can pass only through solids.

Compressional waves are the fastest seismic waves, and they arrive first at a distant point. For this reason, compressional waves are also called primary (P) waves. Shear waves, which travel slower and arrive later, are called secondary (S) waves.

Body waves travel faster deep within Earth than near the surface. For example, at depths of less than 16 miles (25 kilometers), compressional waves travel at about 4.2 miles (6.8 kilometers) per second, and shear waves travel at 2.4 miles (3.8 kilometers) per second. At a depth of 620 miles (1,000 kilometers), the waves travel more than 11/2 times that speed.

Surface waves are long, slow waves. They produce what people feel as slow rocking sensations and cause little or no damage to buildings.

There are two kinds of surface waves: (1) Love waves and (2) Rayleigh waves. Love waves travel through Earth’s surface horizontally and move the ground from side to side. Rayleigh waves make the surface of Earth roll like waves on the ocean. Typical Love waves travel at about 23/4 miles (4.4 kilometers) per second, and Rayleigh waves, the slowest of the seismic waves, move at about 21/4 miles (3.7 kilometers) per second. The two types of waves were named for two British physicists, Augustus E. H. Love and Lord Rayleigh, who mathematically predicted the existence of the waves in 1911 and 1885, respectively.

Damage by earthquakes

How earthquakes cause damage

Earthquakes can damage buildings, bridges, dams, and other structures, as well as many natural features. Near a fault, both the shifting of large blocks of Earth’s crust, called fault slippage, and the shaking of the ground due to seismic waves cause destruction. Away from the fault, shaking produces most of the damage. Undersea earthquakes may cause huge tsunamis that swamp coastal areas. Other hazards during earthquakes include rockfalls, ground settling, and falling trees or tree branches.

Fault slippage

The rock on either side of a fault may shift only slightly during an earthquake or may move several feet or meters. In some cases, only the rock deep in the ground shifts, and no movement occurs at Earth’s surface. In an extremely large earthquake, the ground may suddenly heave 20 feet (6 meters) or more. Any structure that spans a fault may be wrenched apart. The shifting blocks of earth may also loosen the soil and rocks along a slope and trigger a landslide. In addition, fault slippage may break down the banks of rivers, lakes, and other bodies of water, causing flooding.

Ground shaking causes structures to sway from side to side, bounce up and down, and move in other violent ways. Buildings may slide off their foundations, collapse, or be shaken apart.

In areas with soft, wet soils, a process called liquefaction may intensify earthquake damage. Liquefaction occurs when strong ground shaking causes wet soils to behave temporarily like liquids rather than solids. Anything on top of liquefied soil may sink into the soft ground. The liquefied soil may also flow toward lower ground, burying anything in its path.

Tsunamis

An earthquake on the ocean floor can give a tremendous push to surrounding seawater and create one or more large, destructive waves called tsunamis, also known as seismic sea waves. Some people call tsunamis tidal waves, but scientists think the term is misleading because the waves are not caused by the tide. Tsunamis may build to heights of more than 100 feet (30 meters) when they reach shallow water near shore. In the open ocean, tsunamis typically move at speeds of 500 to 600 miles (800 to 970 kilometers) per hour. They can travel great distances while diminishing little in size and can flood coastal areas thousands of miles or kilometers from their source.

Structural hazards

Structures collapse during a quake when they are too weak or rigid to resist strong, rocking forces. In addition, tall buildings may vibrate wildly during an earthquake and knock into each other. Picture San Francisco earthquake of 1906 A major cause of death and property damage in earthquakes is fire. Fires may start if a quake ruptures gas or power lines. The 1906 San Francisco earthquake ranks as one of the worst disasters in United States history because of a fire that raged for three days after the quake.

Other hazards during an earthquake include spills of toxic chemicals and falling objects, such as tree limbs, bricks, and glass. Sewage lines may break, and sewage may seep into water supplies. Drinking of such impure water may cause cholera, typhoid, dysentery, and other serious diseases.

Loss of power, communication, and transportation after an earthquake may hamper rescue teams and ambulances, increasing deaths and injuries. In addition, businesses and government offices may lose records and supplies, slowing recovery from the disaster.

Reducing earthquake damage

In areas where earthquakes are likely, knowing where to build and how to build can help reduce injury, loss of life, and property damage during a quake. Knowing what to do when a quake strikes can also help prevent injuries and deaths.

Where to build

Earth scientists try to identify areas that would likely suffer great damage during an earthquake. They develop maps that show fault zones, flood plains (areas that get flooded), areas subject to landslides or to soil liquefaction, and the sites of past earthquakes. From these maps, land-use planners develop zoning restrictions that can help prevent construction of unsafe structures in earthquake-prone areas.

How to build

An earthquake-resistant building includes such structures as shear walls, a shear core, and cross-bracing. Base isolators act as shock absorbers. A moat allows the building to sway. Image credit: World Book illustration by Doug DeWitt

Engineers have developed a number of ways to build earthquake-resistant structures. Their techniques range from extremely simple to fairly complex. For small- to medium-sized buildings, the simpler reinforcement techniques include bolting buildings to their foundations and providing support walls called shear walls. Shear walls, made of reinforced concrete (concrete with steel rods or bars embedded in it), help strengthen the structure and help resist rocking forces. Shear walls in the center of a building, often around an elevator shaft or stairwell, form what is called a shear core. Walls may also be reinforced with diagonal steel beams in a technique called cross-bracing.

Builders also protect medium-sized buildings with devices that act like shock absorbers between the building and its foundation. These devices, called base isolators, are usually bearings made of alternate layers of steel and an elastic material, such as synthetic rubber. Base isolators absorb some of the sideways motion that would otherwise damage a building.

Skyscrapers need special construction to make them earthquake-resistant. They must be anchored deeply and securely into the ground. They need a reinforced framework with stronger joints than an ordinary skyscraper has. Such a framework makes the skyscraper strong enough and yet flexible enough to withstand an earthquake.

Earthquake-resistant homes, schools, and workplaces have heavy appliances, furniture, and other structures fastened down to prevent them from toppling when the building shakes. Gas and water lines must be specially reinforced with flexible joints to prevent breaking.

Safety precautions are vital during an earthquake. People can protect themselves by standing under a doorframe or crouching under a table or chair until the shaking stops. They should not go outdoors until the shaking has stopped completely. Even then, people should use extreme caution. A large earthquake may be followed by many smaller quakes, called aftershocks. People should stay clear of walls, windows, and damaged structures, which could crash in an aftershock.

People who are outdoors when an earthquake hits should quickly move away from tall trees, steep slopes, buildings, and power lines. If they are near a large body of water, they should move to higher ground. Where and why earthquakes occur

Scientists have developed a theory, called plate tectonics, that explains why most earthquakes occur. According to this theory, Earth’s outer shell consists of about 10 large, rigid plates and about 20 smaller ones. Each plate consists of a section of Earth’s crust and a portion of the mantle, the thick layer of hot rock below the crust. Scientists call this layer of crust and upper mantle the lithosphere. The plates move slowly and continuously on the asthenosphere, a layer of hot, soft rock in the mantle. As the plates move, they collide, move apart, or slide past one another.

The movement of the plates strains the rock at and near plate boundaries and produces zones of faults around these boundaries. Along segments of some faults, the rock becomes locked in place and cannot slide as the plates move. Stress builds up in the rock on both sides of the fault and causes the rock to break and shift in an earthquake.

There are three types of faults: (1) normal faults, (2) reverse faults, and (3) strike-slip faults. In normal and reverse faults, the fracture in the rock slopes downward, and the rock moves up or down along the fracture. In a normal fault, the block of rock on the upper side of the sloping fracture slides down. In a reverse fault, the rock on both sides of the fault is greatly compressed. The compression forces the upper block to slide upward and the lower block to thrust downward. In a strike-slip fault, the fracture extends straight down into the rock, and the blocks of rock along the fault slide past each other horizontally.

Most earthquakes occur in the fault zones at plate boundaries. Such earthquakes are known as interplate earthquakes. Some earthquakes take place within the interior of a plate and are called intraplate earthquakes.

Interplate earthquakes occur along the three types of plate boundaries: (1) mid-ocean spreading ridges, (2) subduction zones, and (3) transform faults.

Mid-ocean spreading ridges are places in the deep ocean basins where the plates move apart. As the plates separate, hot lava from Earth’s mantle rises between them. The lava gradually cools, contracts, and cracks, creating faults. Most of these faults are normal faults. Along the faults, blocks of rock break and slide down away from the ridge, producing earthquakes.

Near the spreading ridges, the plates are thin and weak. The rock has not cooled completely, so it is still somewhat flexible. For these reasons, large strains cannot build, and most earthquakes near spreading ridges are shallow and mild or moderate in severity.

Subduction zones are places where two plates collide, and the edge of one plate pushes beneath the edge of the other in a process called subduction. Because of the compression in these zones, many of the faults there are reverse faults. About 80 per cent of major earthquakes occur in subduction zones encircling the Pacific Ocean. In these areas, the plates under the Pacific Ocean are plunging beneath the plates carrying the continents. The grinding of the colder, brittle ocean plates beneath the continental plates creates huge strains that are released in the world’s largest earthquakes.

The world’s deepest earthquakes occur in subduction zones down to a depth of about 450 miles (700 kilometers). Below that depth, the rock is too warm and soft to break suddenly and cause earthquakes.

Transform faults are places where plates slide past each other horizontally. Strike-slip faults occur there. Earthquakes along transform faults may be large, but not as large or deep as those in subduction zones.

One of the most famous transform faults is the San Andreas Fault. The slippage there is caused by the Pacific Plate moving past the North American Plate. The San Andreas Fault and its associated faults account for most of California’s earthquakes.

Intraplate earthquakes are not as frequent or as large as those along plate boundaries. The largest intraplate earthquakes are about 100 times smaller than the largest interplate earthquakes.

Intraplate earthquakes tend to occur in soft, weak areas of plate interiors. Scientists believe intraplate quakes may be caused by strains put on plate interiors by changes of temperature or pressure in the rock. Or the source of the strain may be a long distance away, at a plate boundary. These strains may produce quakes along normal, reverse, or strike-slip faults.

Studying earthquakes

Recording, measuring, and locating earthquakes

To determine the strength and location of earthquakes, scientists use a recording instrument known as a seismograph. A seismograph is equipped with sensors called seismometers that can detect ground motions caused by seismic waves from both near and distant earthquakes. Some seismometers are capable of detecting ground motion as small as 0.1 nanometer. One nanometer is 1 billionth of a meter or about 39 billionths of an inch. Scientists called seismologists measure seismic ground movements in three directions: (1) up-down, (2) north-south, and (3) east-west. The scientists use a separate sensor to record each direction of movement.

A seismograph produces wavy lines that reflect the size of seismic waves passing beneath it. The record of the wave, called a seismogram, is imprinted on paper, film, or recording tape or is stored and displayed by computers.

Probably the best-known gauge of earthquake intensity is the local Richter magnitude scale, developed in 1935 by United States seismologist Charles F. Richter. This scale, commonly known as the Richter scale, measures the ground motion caused by an earthquake. Every increase of one number in magnitude means the energy release of the quake is about 32 times greater. For example, an earthquake of magnitude 7.0 releases about 32 times as much energy as an earthquake measuring 6.0. An earthquake with a magnitude of less than 2.0 is so slight that usually only a seismometer can detect it. A quake greater than 7.0 may destroy many buildings. The number of earthquakes increases sharply with every decrease in Richter magnitude by one unit. For example, there are 8 times as many quakes with magnitude 4.0 as there are with magnitude 5.0.

Although large earthquakes are customarily reported on the Richter scale, scientists prefer to describe earthquakes greater than 7.0 on the moment magnitude scale. The moment magnitude scale measures more of the ground movements produced by an earthquake. Thus, it describes large earthquakes more accurately than does the Richter scale.

The largest earthquake ever recorded on the moment magnitude scale measured 9.5. It was an interplate earthquake that occurred along the Pacific coast of Chile in South America in 1960. The largest intraplate earthquakes known struck in central Asia and in the Indian Ocean in 1905, 1920, and 1957. These earthquakes had moment magnitudes between about 8.0 and 8.3. The largest intraplate earthquakes in the United States were three quakes that occurred in New Madrid, Missouri, in 1811 and 1812. The earthquakes were so powerful that they changed the course of the Mississippi River. During the largest of them, the ground shook from southern Canada to the Gulf of Mexico and from the Atlantic Coast to the Rocky Mountains. Scientists estimate the earthquakes had moment magnitudes of 7.5.

Scientists locate earthquakes by measuring the time it takes body waves to arrive at seismographs in a minimum of three locations. From these wave arrival times, seismologists can calculate the distance of an earthquake from each seismograph. Once they know an earthquake’s distance from three locations, they can find the quake’s focus at the center of those three locations.

Predicting earthquakes

Scientists can make fairly accurate long-term predictions of where earthquakes will occur. They know, for example, that about 80 percent of the world’s major earthquakes happen along a belt encircling the Pacific Ocean. This belt is sometimes called the Ring of Fire because it has many volcanoes, earthquakes, and other geologic activity.

Scientists are working to make accurate forecasts on when earthquakes will strike. Geologists closely monitor certain fault zones where quakes are expected. Along these fault zones, they can sometimes detect small quakes, the tilting of rock, and other events that might signal a large earthquake is about to occur.

Exploring Earth’s interior

Most of what is known about the internal structure of Earth has come from studies of seismic waves. Such studies have shown that rock density increases from the surface of Earth to its center. Knowledge of rock densities within Earth has helped scientists determine the probable composition of Earth’s interior.

Scientists have found that seismic wave speeds and directions change abruptly at certain depths. From such studies, geologists have concluded that Earth is composed of layers of various densities and substances. These layers consist of the crust, mantle, outer core, and inner core. Shear waves do not travel through the outer core. Because shear waves cannot travel through liquids, scientists believe the outer core is liquid. Scientists believe the inner core is solid because of the movement of compressional waves when they reach the inner core. Contributor: Karen C. McNally, Ph.D., Professor of Earth Sciences, University of California, Santa Cruz.

How to cite this article: To cite this article, World Book recommends the following format: McNally, Karen C. “Earthquake.” World Book Online Reference Center. 2005. World Book, Inc. http://www.worldbookonline.com/wb/Article?id=ar171680.

source:http://www.nasa.gov

Ocean Topography from Space

Our home, the Earth, experiences some of the most varied and interesting weather in the Solar System. This is because the Earth is actually a water-world, with some 70% of its surface covered by a vast, deep ocean. The world-ocean is a huge sink for solar energy. Through currents the ocean transports this energy as heat, and releases it back into the atmosphere as water vapor, which is then returned back to the oceans and land as rain or snow. This completes the hydrologic cycle.

How can we measure and track changes in the oceanic heat-budget? We need to know both ocean currents and heat storage of the ocean. Like winds blow around the highs and lows of atmospheric pressure, ocean currents flow around highs and lows of oceanic pressure that can be determined from the height of sea surface, called ocean surface topography. Ocean current velocity can thus be computed from the slope of the ocean surface. Furthermore, as water heats up, it expands, and as it cools, it contracts, affecting the height of sea surface as well. Measuring the ocean surface topography thus gives the required information for studying global ocean circulation and the oceans heat budget. Regular scanning of the ocean surface to maintain a database of ocean surface topography can help predict short-term changes in weather and longer-term patterns of climate.

Ocean heating up

Overview - Ocean Surface Topography

Topography is the configuration of a surface, including its relief. The topography of the sea surface is influenced by both gravity and ocean circulation.

Artist’s illustration of ocean surface topography

The actual shape of the Earth is not a perfect sphere — it’s not even a perfect ellipsoid (which would account for the effect of its rotation). If you measure the strength of the gravity field across the Earth’s surface, you will find local variations caused by irregularities in the crust, which produce an irregular figure called the geoid — the actual shape of the Earth. To find the surface caused by ocean circulation, we mathematically remove the sea height caused by gravity (the geoid) and create maps of ocean topography. We then calculate the speed and direction of ocean currents similar to how meteorologists use atmospheric pressure maps to calculate winds.

Altimetry is the measurement of the height of the sea surface above (or below) some reference level. Every 10 days, Jason-1 measures heights of more than 90% of the world’s ice-free oceans with the radar altimeter and completes 127 revolutions, or orbits, around the Earth.

To measure sea surface height we need the satellite’s position in its orbit and the height between the satellite and the ocean’s surface. We may also have to correct for variable amounts of water vapor in the lower atmosphere and free electrons in the upper atmosphere. Both of these can delay microwave pulses.

To learn more visit these sites:
http://topex-www.jpl.nasa.gov/overview/overview.html
http://topex-www.jpl.nasa.gov/overview/topography.html

SOURCE:http://www.nasa.gov

The Structure of the Ocean Floor(Ocean Topography)

The study of landforms is the science of topography. When we speak of the topography of the ocean floor, we mean the various shapes that the bottom of the ocean can take. We tend to picture the ocean floor as being as flat and sandy as the beaches with which we are familiar. Fortunately, the ocean floor isn’t quite that simple, predictable, or boring. Though the bottom of the ocean is hidden from our sight by vast quantities of water, it’s anything BUT boring, flat and featureless. Maps like the one above are giving us increasingly detailed views of the ocean floor. As our technological expertise increases, so does our ability to visualize these distant landscapes. We find basically that the ocean floor has all the same shapes, bumps, mountains, valleys, plateaus and such that we are more familiar with on the surface. When you consider that three quarters of our planet’s surface is covered by ocean water, you soon realize that there’s more land “down there” than we have “up here”. It really isn’t all that different from the land on which you and I live.

As the continent ends and we approach the ocean, we see some drastic changes in the Earth’s geology. This transitional area is known as the CONTINENTAL MARGIN. This area includes both the continental shelf and the continental slope. Even the very rock with which the Earth is made changes. The heavy and thick continental granite gives way to a thinner layer of basalt. As you first proceed into the water, you are standing on the continental shelf. This gradually sloping and shallow area generally contains water that is only a couple of hundred feet deep. The NERETIC ZONE is located here. The width of the continental shelf varies greatly depending on location. The width of the continental shelf varies greatly depending on location. Off the coast of Maine, the shelf extends for about 200 kilometers. In other places, like the Atlantic coast of Florida, the continental shelf is very narrow, somewhere in the 1 -2 kilometer range, or less. As you pass the edge of the continental shelf, you will notice that the floor begins a steep descent. This steeply sloping portion is called the CONTINENTAL SLOPE. The continental slope marks the boundary between the continental type granite crust and the oceanic basaltic crust. Occasionally, you will observe deep “V” -shaped valleys cut into the hard rock of the continental slope. These are called SUBMARINE CANYONS. Geologists speculate that these canyons are formed due to seismic activity, or perhaps eroded into the rock of the slope by powerful ocean currents.

As the slope begins to level out, you approach the ocean basin. The ocean basin also has some interesting topography to examine. Perhaps the most unusual are the ABYSSAL PLAINS. These are large, flat areas on the ocean floor covered with a thick layer of sediment and decomposing organic “ooze”. Abyssal plains are larger in the Atlantic ocean than they are in the Pacific. The reason for this is that many of the world’s major sediment carrying rivers empty into the Atlantic and Indian Oceans. Also, the Pacific ocean is ringed with large trenches which act as traps for the sediments. Large, undersea volcanoes called SEAMOUNTS occasionally rise from the depths. Sometimes the peaks of these giant underwater volcanoes reach to the surface to form volcanic islands. The island of Hawaii is really the top of a seamount that is over 9,600 meters tall! The tallest mountain on Earth!

About 20,000 years ago, during the last Ice Age, much of the ocean’s water was frozen in the form of vast glaciers. As a result, the ocean’s level was lower than it is today. Much of the Earth’s freshwater was tied up in the massive ice pack covering large parts of the continents. As a result, there was less water involved in the Hydrologic Cycle, so the ocean’s were lower, much lower, to the tune of about 300 feet less than today. Wave action neatly eroded the tops of some existing seamounts, causing them to eventually have flat tops. When the large ice sheets melted, the water returned to the ocean, and the ocean levels rose. Today we see many GUYOTS present around 300 feet below the ocean’s surface. These flat-topped seamounts are constant reminders of the Earth’s diverse history, and its ever-changing present and future.

OCEAN TRENCHES are found along the edge of ocean basins. These trenches contain the deepest parts of the ocean, and therefore, the deepest parts of this wonderful world. The deepest spot on Earth is located in the western Pacific, near Guam in the Mariana Trench. The exact location is called CHALLENGER DEEP and the water there is 11,033 meters deep! That’s nearly seven miles of water!!! Seven miles is a long way, particularly when we remember that sunlight can penetrate maybe only 1500 feet or so down. Who knows what mysteries lie unsolved this deep beneath the waves. What discoveries await from this ecosystem so far removed from the warm yellow light of our sun? At one time, people would have told you that nothing could possibly exist at these depths. Yet, we’ve seen entire ecosystems living in the deepest parts of the ocean, functioning independently of the sun’s light, upon which we surface creatures depend so much. The most exciting times lie ahead of us in our exploration of the oceans of this wonderful world!

Ocean

An ocean (from Ωκεανός, Okeanos (Oceanus) in Greek) is a major body of saline water, and a principal component of the hydrosphere. Approximately 71% of the Earth’s surface (an area of some 361 million square kilometers) is covered by ocean, a continuous body of water that is customarily divided into several principal oceans and smaller seas. More than half of this area is over 3,000 meters (9,800 ft) deep. Average oceanic salinity is around 35 parts per thousand (ppt) (3.5%), and nearly all seawater has a salinity in the range of 31 to 38 ppt.

source:http://en.wikipedia.org/wiki/Ocean

<a href=”http://www.mybloglog.com/buzz/community/rashidsblog/” rel=”9c191153f0fb96fab19c5318259abbc3239b7128″>Undergoing MyBlogLog Verification</a>