GEOGRAPHY
In geology , a fault is a planar fracture or discontinuity in a volume of rock , across which there has been significant displacement. Large faults within the Earth's crust result from the action of tectonic forces. Energy release associated with rapid movement on active faults is the cause of most earthquakes , such as occurs on the San Andreas Fault , California .
A fault line is the surface trace of a fault, the line of intersection between the fault plane and the Earth's surface.
[1]
Since faults do not usually consist of a single, clean fracture, geologists use the term fault zone when referring to the zone of complex deformation associated with the fault plane.
The two sides of a non-vertical fault are known as the hanging wall and footwall . By definition, the hanging wall occurs above the fault plane and the footwall all occurs below the fault.
[2] This terminology comes from mining: when working a tabular ore body, the miner stood with the footwall under his feet and with the hanging wall hanging above him.
[3]
List Of Active Fault Lines In The Philippines
1. Marikina Valley Fault (Montalban, San Mateo, Marikina, Pasig, Taguig, Muntinlupa, San Pedro, Binan, Carmona, Santa Rosa,
Calamba, Tagaytay, Oriental Mindoro)
2. Western Philippine Fault (Luzon Sea, Mindoro Strait, Panay Gulf, Sulu Sea)
3. Eastern Philippine Fault (Philippine Sea)
4. Southern of Mindanao Fault (Moro Gulf, Celebes Sea)
5. Central Philippine Fault (Entire Ilocos Norte, Aurora, Quezon, Masbate, Eastern Leyte, Southern Leyte, Agusan Del Norte,
Agusan Del Sur, Davao del Norte)
Of these, the MARIKINA VALLEY FAULT poses the greatest danger because it cuts through all the modern and progressive portions of
Manila such as Eastwood, Rockwell, Ortigas Center, Bonifacio Global City, Ayala Center, and Alabang. Also, the PhiVolcs people have warned that this fault line can move anytime because it is already “11 years late” for its movement.
*The earthquake that destroyed Guinsaugon is the Central Philippine Fault
*The 1990 earthquake that destroyed Central Luzon and Baguio is also the Central Philippine Fault.
An equinox occurs twice a year, when the tilt of the Earth 's axis is inclined neither away from nor towards the Sun , the center of the Sun being in the same plane as the Earth's equator . The term equinox can also be used in a broader sense, meaning the date when such a passage happens. The name "equinox" is derived from the Latin aequus (equal) and nox (night), because around the equinox, the night and day have approximately equal length.
At an equinox, the Sun is at one of two opposite points on the celestial sphere where the celestial equator (i.e. declination 0) and ecliptic intersect. These points of intersection are called equinoctial points: classically, the vernal point and the autumnal point .
By extension, the term equinox may denote an equinoctial point.
An equinox happens each year at two specific moments in time (rather than two whole days), when there is a location (the subsolar point ) on the Earth's equator, where the center of the Sun can be observed to be vertically overhead, occurring around March 20/21 and September 22/23 each year.
Although the word equinox is often understood to mean "equal [day and] night," this is not strictly true. For most locations on earth, there are two distinct identifiable days per year when the length of day and night are closest to being equal; those days are referred to

as the "equiluxes" to distinguish them from the equinoxes. Equinoxes are points in time, but equiluxes are days. By convention, equiluxes are the days where sunrise and sunset are closest to being exactly 12 hours apart.
[2][3]
Names

Vernal equinox and autumnal equinox : these classical names are direct derivatives of Latin
( ver = spring and autumnus = autumn ).

March equinox and September equinox : a usage becoming the preferred standard by technical writers choosing to avoid Northern Hemisphere bias (implied by assuming that March is in the springtime and September is autumnal
—true for those in the Northern Hemisphere but exactly opposite in the Southern Hemisphere ).

Northward equinox and southward equinox : names referring to the apparent motion of the Sun at the times of the equinox.

Vernal point and autumnal point are the points on the celestial sphere where the Sun is located on the vernal equinox and autumnal equinox respectively (again, the seasonal attribution is that of the Northern Hemisphere).

First point (or cusp ) of Aries and first point of Libra are names used by navigators and astrologers . Navigational ephemeris tables record the geographic position of the First Point of Aries as the reference for position of navigational stars. Due to the precession of the equinoxes , the astrological signs of the tropical zodiac where these equinoxes are located no longer correspond with the actual constellations once ascribed to them. The equinoxes are currently in the constellations of Pisces and Virgo . However, modern tropical astrologers assert that the tropical zodiac, and thus 0º degrees Aries, always begins at the Vernal Equinox. Such modern astrologers see the zodiacal signs as 30º segments of the tropical zodiac, always beginning with the Spring equinoctial point, so that the astrological zodiac has no relation to the stars, there being therefore no discrepancy due to precession.
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
EnchantedLearning.com
The Seasons and Axis Tilt



The Earth's seasons are not caused by the differences in the distance from the Sun throughout the year (these differences are extremely small). The seasons are the result of the tilt of the Earth's axis.


The Earth's axis is tilted from perpendicular to the plane of the ecliptic by 23.45°. This tilting is what gives us the four seasons of the year - spring, summer, autumn (fall) and winter. Since the axis is tilted, different parts of the globe are oriented towards the Sun at different times of the year.

Summer is warmer than winter (in each hemisphere) because the Sun's rays hit the Earth at a more direct angle during summer than during winter and also because the days are much longer than the nights during the summer.
During the winter, the Sun's rays hit the Earth at an extreme angle, and the days are very short. These effects are due to the tilt of the Earth's axis.

Solstices
The solstices are days when the Sun reaches its farthest northern and southern declinations. The winter solstice occurs on December 21 or 22 and marks the beginning of winter (this is the shortest day of the year). The summer solstice occurs on June 21 and marks the beginning of summer (this is the longest day of the year).

Equinoxes
Equinoxes are days in which day and night are of equal duration. The two yearly equinoxes occur when the Sun crosses the celestial equator.

The vernal equinox occurs in late March (this is the beginning of spring in the Northern Hemisphere and the beginning of fall in the Southern Hemisphere); the autumnal equinox occurs in late September (this is the beginning of fall in the Northern Hemisphere and the beginning of spring in the Southern Hemisphere)
The earths axis
Earth's axis is the imaginary line which goes through the north and south poles and around which Earth spins. It is inclined 66.5 degrees from Earth's orbital plane, 1 which means that it is tilted 23.5 degrees from a vertical 90 degrees.
Generally, an axis is any imaginary or physical line that prescribes an object's movement. A taut string that goes through the center of a spinning ball would be an example of a physical axis. The string, as the axis, would represent the part of the ball that is not really moving or that is moving the least.
An axis also includes the point that is known as the center of gravity.
Note: There are comments associated with this question. See the discussion page to add to the conversation.
Time Determination
Before the dawn of recorded history, humans recognized that the position of the sun in the sky is an indication of the progress of the day.
As one's knowledge of the earth and its relation to the sun increased, so did the sophistication of the devices used in timekeeping. Alfred the Great used "good tall candles," divided into equal segments. As they burned, they showed the time of day or night. The first clock in the modern sense was constructed by Huyghens, who used Galileo's discovery of the pendulum for it, For centuries the position of the real sun in the sky was used to tell time.
This is called apparent solar time. "High noon" or 12 o'clock is the highest altitude the sun will achieve on that particular day,
Watches and clocks are really reading the kind of time that the sun would keep if its motion were uniform; that is, mean solar time. For many decades mean solar time was used successfully, but with the advent of more rapid transportation, difficulties increased.
When transportation was by horse or by sailboat, it was not necessary- in fact very difficult- to predict the arrival time on a long journey within a few minutes. Once the "Iron Horse" began making transcontinental journeys with many stops along the way, timetables expressed in local solar time became a gigantic headache and a nightmare of confusion.
This is what led to the idea of Standard Time, Sir Sanford Fleming , a Canadian railway engineer, was largely responsible for this idea that was adopted worldwide in 1884. It was agreed to establish 24 international time zones at 15 degree intervals around the world starting at Greenwich, England. The 20th century improvement on Standard Time has been the introduction of Daylight Time, "Spring ahead and Fall back"
It is most interesting to note that Fleming really wanted "universal time" implemented.
The Year and the Calendar
Two principal calendars have been used for many centuries. One is based on the sun's annual path; the other, on the moon's monthly path- in particular, its phases.


Our present calendar is based on the numerical value of the tropical year, 365 days, 5 hours, 48 minutes, 46 seconds. It was introduced by Julius Caesar with the help of the astronomer Sosigenes.
They developed the idea of Leap Years to adjust the calendar to coincide with the seasons. Calendars were altered in 1582 and 1752 to adjust for some extra days that had accumulated.
For many years, further calendar reformers have suggested a 13 month year containing 28 days each.
Another reform suggests 4 equal quarters in a year with a first month of 31 days. The second and third months would have 30 days and the fourth ends on a Saturday, Both systems require extra leap days. With our present system of timekeeping it is actually possible to have 10 Sundays in FebruarY
Learn the scientific reasons behind Earth's seasons
Our planet’s tilt dictates cycle of summer and winter
At sunrise on the summer solstice, June 21, druids, pagans and partygoers converge on a circle of stones in the English countryside to welcome the longest day of the year. The ritual at Stonehenge likely dates back thousands of years: Archaeologists estimate wooden posts and timbers were in place as early as 3100 B.C., although the monument's original purpose remains a mystery. One theory holds that it was a cemetery; another that it was a place of healing. Most archaeologists believe the large sarsen stones in the post-and-lintel formations seen in the background of this image served to mark the seasons, making Stonehenge an astronomical observatory as well as a religious center of one sort or another. Click the "Next" label for nine more slices of summer science.
— By John Roach, msnbc.com contributor
By Paige Williams msnbc.com updated 6/20/2011 11:10:42 PM ET
The seasons are a powerful force in our lives. They affect the activities we do, the foods we crave, the clothes we wear — and quite often, the moods we are in. The seasons officially change once again Tuesday, with summer beginning in the Northern Hemisphere and winter starting in the south.
What is it that causes the change in seasons?
The ability to predict the seasons — by tracking the rising and setting points of the sun throughout the year — was key to survival in ancient times. The Babylonians, the Maya and other cultures developed complex systems for monitoring seasonal shifts. But it took centuries more to unravel the science behind the seasons.
Nicolai Copernicus (1473-1543) radically changed our understanding of astronomy when he proposed that the sun, not Earth, was the center of the solar system. This led to our modern understanding of the relationship between the sun and Earth.
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We now know that Earth orbits the sun elliptically and, at the same time, spins on an axis that is tilted relative to its plane of orbit. This means that different hemispheres are exposed to different amounts of sunlight throughout the year. Because the sun is our source of light, energy and heat, the changing intensity and concentration of its rays give rise to the seasons of winter, spring, summer and fall.
Solstices and equinoxes
The seasons are marked by solstices and equinoxes
— astronomical terms that relate to Earth’s tilt.

The solstices mark the points at which the poles are tilted at their maximum toward or away from the sun. This is when the difference between the daylight hours and the nighttime hours is most acute. The solstices occur each year on June 20 or 21 and Dec. 21 or 22, and represent the official start of the summer and winter seasons.
The vernal equinox and autumnal equinox herald the beginning of spring and fall, respectively. At these times of the year, the sun appears to be directly over Earth’s equator, and the lengths of the day and the night are equal over most of the planet.
On March 20 or 21 of each year, the Northern Hemisphere reaches the vernal equinox and enjoys the signs of spring. At the same time, the winds turn colder in the Southern Hemisphere as the autumnal equinox sets in.
The year's other equinox occurs on Sept. 22 or 23, when summer fades to fall in the north, and winter’s chill starts giving way to spring in the south.
From year to year, there is always some variability in the equinoxes and solstices because of the way Earth's changing tilt matches up with its orbit around the sun. This year, the precise moment of the June solstice comes at 1:16 p.m. ET Tuesday. That's the moment when Earth's north pole is tipped precisely toward the sun.
Tuesday represents the longest day of the year for the Northern Hemisphere's residents, and the longest night of the year south of the equator.
Here’s how the seasonal change affects the weather: Around the time of the June solstice, the North Pole is tilted toward the sun and the Northern Hemisphere is starting to enjoy summer. The density of the solar radiation is higher because it's coming from directly overhead
— in other words, the sun's rays are concentrated over a smaller surface area. The days are longer, too, meaning that more radiation is absorbed in northern climes during the 24-hour cycle. Another factor that may come into play is that the radiation takes a somewhat shorter path through the energy-absorbing atmosphere before striking the earth.
NASA
This montage of satellite imagery shows how vegetation changes on Earth with the seasons.
At the same time that the Northern Hemisphere is entering summer, the South Pole is tilted away from the sun, and the Southern
Hemisphere is starting to feel the cold of winter. The sun’s glancing rays are spread over a greater surface area and must travel through more of the atmosphere before reaching the earth. There are also fewer hours of daylight in a 24-hour period.
The situations are rev ersed in December, when it’s the Southern Hemisphere that basks in the most direct rays of the sun, while the
Northern Hemisphere receives less dense solar radiation for shorter periods of time.
Although the solstices represent the pinnacles of summer and winter with respect to the intensity of the sun’s rays, they do not usually represent the year's warmest or coldest days. This is because temperature depends not only on the amount of heat the atmosphere receives from the sun, but also on the amount of heat it loses due to the absorption of this heat by the ground and ocean.
It is not until the ground and oceans absorb enough heat to reach equilibrium with the temperature of the atmosphere that we feel the coldest days of winter or hottest days of summer.
This is an updated version of an article originally published in March 1999.

THE FACE OF THE EARTH
The Face Of The Earth by Thomas Fritz
Bonn, Germany (SPX) Aug 30, 2010
For a month now, we have been acquiring altitude models with the TanDEM-X
Mount Teide, Tenerife. 3D view of a TanDEM-X digital elevation model combined with radar intensity data. and TerraSAR-X satellite pair. Already, over 1000 products have come out of our operational processing chain. Alongside many test images, some of the
Credit: DLR. To see the other images mentioned in the body of this article please go here . data also give an insight into how humankind has shaped the surface of the
Earth - and how the highs and lows around them have determined the course of their lives.
Many of the interferometric images created over the last few weeks have used test data acquired over flat areas to enable us to test the stability and precision of our imaging and processing chains with minimal altitude changes. Some of the images, on the other hand, have been of exceptionally complicated terrain, in order to test the transformation of interferograms into altitude data.
The satellites are still not flying in close formation with synchronous data acquisition, so the ultimate altitude precision cannot yet been achieved. Also, the final steps for calibrating the processing chain have not yet been performed. Nevertheless, the images are already of impressive quality and are showing us details that were not previously visible from space.
We in the processing team have always enjoyed activating the display software in the processor and looking not just at a dry series of numbers but also at the 3D elevation models (Digital Elevation Models; DEMs) that the software produces.
There are several ways we can look at the 3D structure of the terrain. The images on this page use the radar signal (backscatter) intensity to determine the brightness of the image and the altitude of the terrain to select the colour (from blue-green to red-brown and then white).
Of course, the computer can also 'look' at the DEM from an oblique angle to achieve a 3D-effect, with the heights exaggerated for clarity.
The example of the 3718-metre high Mount Teide, on the island of Tenerife, shows particularly well how the two radar satellites perceive the landscape. The satellites imaged the island at an angle from the left, and the dark shadows in the valleys are areas that the radar signals could not reach, while the bright sides of the mountain were fully illuminated.
Shadows and the deformations typical of radar signals make it difficult for the processor to calculate the correct altitudes; so, in later phases of the mission, other viewing angles will be used to fill the gaps.
The influence of human activity can be seen here in the bright settlements and agricultural land that nestle along the coast beneath the volcano. This view is far from showing the full potential of the new generation of DEMs made possible by TanDEM-X.

A smaller detail from a view of the Bavarian region around our facility at Oberpfaffenhofen and its nearby airport is shown here at only one-eighth of the full resolution of the raw data, and yet it still shows the effect of human activity in the altitude data. Farms and towns have eaten into the forests and a number of high buildings, motorways and railway lines can be recognised.
No one could fail to see the effect of human activity in the opencast mining area between Cologne and Aachen. The mines and spoil heaps are several kilometres across. While human activity has formed the landscape here, in other parts of the world an altitude difference of just a few metres - or even centimetres - can be of vital importance.
One of our DEMs, created on 6 August in the Khairabad region of northern Pakistan, shows how extended the low-lying areas on the banks of the River Indus can be. These potential flood zones - clearly visible in the image - are inhabited. Here too we have exaggerated the altitude scale to make the relatively small differences clear.
Our processor does not just produce DEMs; even during the current commissioning phase, a number of interferometric experiments are being analysed by scientists at DLR and elsewhere. One example is the Petermann Glacier in northern Greenland, from which a gigantic iceberg has recently broken off - making The Face Of The Earths around the world.
In this case, the interferometric phase shows not just the contour lines, but also signs of a small movement of the ice in the threesecond period between the two satellite image acquisitions (indicated by the rapid change of colour on the smaller ice floes). Data like this enable scientists to determine the drift of ice and are important inputs to the areas of climate dynamics and the interaction between the sea and glacial ice
THE EARTH LANDMASSES AND LANDFORMS
Landforms are the mesoscale topographic features that define a regional landscape. Climate and plate tectonics ultimately determine the system of processes —plate tectonic motion, gravity, erosion , and deposition by water , wind , and ice
—that interact in complex feedback loops to erect and destroy continental landforms. Climate, the regional pattern of seasonal precipitation , temperature, and wind-flow, varies with latitude, altitude, and physiographic location. Motion of Earth's lithospheric plates , called plate tectonics, determines the global geography of mountain chains , volcanoes, continental landmasses, and ocean basins, as well as the distribution of rock types. The morphology of landforms suggests the processes that created them, and landforms are clues to deciphering the present and past geological setting of a region.
Climate often dictates the mix of sedimentary processes acting to create landforms. For example, eolian, or wind-formed, landforms are common in arid environments, whereas glacial landforms like moraines and kettle ponds are found in cold regions with adequate snowfall. The abundance and seasonality of annual rainfall determines the intensity of weathering and erosion by flowing water. In rainy regions, a dendritic pattern of V-shaped stream valleys often dominates the landscape. Low-gradient stream valleys are filled with fluvial landforms like meandering channels, oxbow lakes , natural levees, and point bars, while sediment-choked mountain streams form broad, gravelly plains of intertwined channels and longitudinal bars.
Air currents also shape landscapes by sorting and reworking dry sediments in arid environments. Eolian land-forms include numerous types of sand dunes: cresent-shaped barchans, merged barchans called transverse dunes, parabolic blowout pits, flow-parallel linear dunes, and large composite dunes called draas. Very large dune fields called ergs cover extensive areas of the major deserts.
Seasonal temperature fluctuations affect the phase of water. Erosion by frozen surface water creates dramatic glacial features like fjords , hanging valleys, and cirques in high-latitude regions. Evaporation of standing water in hot, arid, desert environments forms a unique array of desert landforms, including ephemeral playa lakes and coarse-grained alluvial fans where mountain streams enter arid basins.
The tectonic plate setting and past geology of a region also affects its topography. Motion along tectonic plate boundaries creates tall mountain belts, volcanic chains, regions of broad uplift, and zones of subsidence. Escarpments, extensional valleys called grabens and pull-apart basins, and linear pressure ridges form along fault planes where rocks bodies move relative to one another. Gravity failure of tectonically over-steepened slopes creates mass wasting deposits like mudflows, slumps, and slides. Streams that follow out-crop patterns of folded sedimentary and metamorphic rocks create ridge and valley provinces. Resistant layers of horizontal strata in tectonically uplifted areas form broad tablelands. Caves, sinkholes , and other so-called karst features form when acidic rainwater falls on carbonate rock layers. Volcanic activity creates numerous distinctive landforms, including craters, lava flows, eroded volcanic necks, and, of course, the conical or shield-shaped volcanoes themselves. Beach and shoreline dynamics along continental margins form an array of coastal landforms, from erosional sea cliffs and stacks to depositional deltas, barrier islands , and spits.

The continents can be divided into physiographic land-form provinces delineated by plate tectonic features and climatic zones.
( Antarctica is an exception because ice covers about 90 percent of its land surface.) The Colorado Plateau, in the southwest United
States, is an example of one such province, and a tour of its dramatic landscape illustrates the complex web of processes acting to sculpt its landforms. The Four Corners region is arid because the prevailing Pacific westerly winds have dropped most of their moisture in the high Sierras of California and Mexico before reaching it. Streams flowing onto the Plateau from the Rocky Mountains, however, provide ample erosional and depositional energy. The Plateau is a broad zone of tectonic uplift that has exposed a thick sequence of flat-lying sedimentary strata to deep incision of steep-walled canyons by flood-prone streams. Erosional remnants like flat-topped mesas, conical buttes, arches, and spires remain between the incised fluvial channels. Winds sort and transport grains of siliciclastic sand, creating dunes and sandblasting the landscape.
Humans have also affected landscape evolution in the modern southwest desert. Construction of dams along the major rivers , especially along the Colorado River, has led to stream regrading and a resulting change in the pattern of fluvial erosional and depositional landforms. Evaporation from man-made reservoirs, like Lake Powell and Lake Mead, has reduced the amount of water in downstream river segments and increased the humidity around the lakes. Water use by human cities, industries, and especially irrigated agricultural lands has changed the regional hydrologic cycle
The top solid layer of the earth is called crust. This forms the earth’s surface. There are high places or elevations-mountains, volcanoes, hills, islands and other landforms that project out of the bodies of water.
There are large and small masses of land. The largest land masses are called continents. There are seven continents. The Philippines belongs to the continent ofAsia. Some land masses are uninhabited by man.
Mountain

It is around 3,000 meters above sea level.

It is the highest form of land. Mt. Apo is the highest mountain in our country.

Mountains are usually covered with forests. Many minerals deposits are found in the mountains.
Volcano

It is a mountain formed when magma from the deepest part of the earth rises up to the surface.

When a volcano erupts, it spits of throw out burn rocks or lava, volcanic ash, heated gases, and steam from its crater.

Lava and volcanic ash make the soil around the volcano fertile.
Hill

It is similar to a mountain in shape but it is lower. It is about 300 meters high.

Hills are usually covered with grass. They are useful as grazing lands for cattle, goats and carabaos.
Plateau

It is as high land with a plain top.
Plain

Is a wide, flat, low land.

It is a place where farm crops are grown well.

Valley

It is also a flat land, but unlike a plain, a valley is surrounded by high lands.

This kind of land is fertile too.
Island

It is a body of land surrounded by water.

The Philippines is composed of more than 7,000 islands.

A group of islands are called archipelago .
Peninsula

It is a portion of land nearly

It is connected to the
Delta

It is a land formation at the mouth of a river.

It contains rich soil which has been washed away and deposited by running water.
Isthmus

It is a strip or neck of land formation that connects two larger bodies of land. surrounded by water. mainland by a strip of a land.
refers to the total area of a country or geographical region (which may include discontinuous pieces of land such as islands ). The Earth 's total land mass is 148,939,063.133 km² (57,511,026.002 square miles) which is about 29.2% of its total surface. Water covers approximately 70.8% of the Earth's surface, mostly in the form of oceans.
Awarded Answer (
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Answer 1 / 2 - Submitted 947 days ago...
Mtnrescue
Brain (2,706)
Total land mass of the earth is
148,939,063.133 km² (57,511,026.002 square miles). That's about
29.2% of the earth's surface. Rest is water. As for dwellings, I'm not sure if anyone's ever figured that out. I suppose if you made an assumption on total land area inhabited and came up with an average ratio between dwelling space and inhabited area you could approximate.
Waters of the earth

The atmosphere
The atmosphere of Earth is a layer of gases surrounding the planet Earth that is retained by Earth's gravity .
The atmosphere protects life on Earth by absorbing ultraviolet solar radiation , warming the surface through heat retention ( greenhouse effect ), and reducing temperature extremes between day and night (the diurnal temperature variation ).
Atmospheric stratification describes the structure of the atmosphere, dividing it into distinct layers, each with specific characteristics such as temperature or composition. The atmosphere has a mass of about 5×10 18 kg, three quarters of which is within about 11 km
(6.8 mi; 36,000 ft) of the surface. The atmosphere becomes thinner and thinner with increasing altitude , with no definite boundary between the atmosphere and outer space . An altitude of 120 km (75 mi) is where atmospheric effects become noticeable during atmospheric reentry of spacecraft. The
Kármán line
, at 100 km (62 mi), also is often regarded as the boundary between atmosphere and outer space.
Air is the name given to atmosphere used in breathing and photosynthesis . Dry air contains roughly (by volume) 78.09% nitrogen ,
20.95% oxygen , 0.93% argon , 0.039% carbon dioxide , and small amounts of other gases. Air also contains a variable amount of water vapor , on average around 1%. While air content and atmospheric pressure varies at different layers, air suitable for the survival of terrestrial plants and terrestrial animals is currently only known to be found in Earth's troposphere and artificial atmospheres.
Structure of the atmosphere
[ edit ] Principal layers
Layers of the atmosphere (not to scale)
In general, air pressure and density decrease in the atmosphere as height increases. However, temperature has a more complicated profile with altitude. Because the general pattern of this profile is constant and recognizable through means such as balloon soundings , temperature provides a useful metric to distinguish between atmospheric layers. In this way, Earth's atmosphere can be divided into five main layers. From highest to lowest, these layers are:
[ edit ]Exosphere
Main article: Exosphere
The outermost layer of Earth's atmosphere extends from the exobase upward. It is mainly composed of hydrogen and helium. The particles are so far apart that they can travel hundreds of kilometers without colliding with one another. Since the particles rarely collide, the atmosphere no longer behaves like a fluid. These free-moving particles follow ballistic trajectories and may migrate into and out of the magnetosphere or the solar wind .
[ edit ]Thermosphere
Main article: Thermosphere
Temperature increases with height in the thermosphere from the mesopause up to the thermopause , then is constant with height.
Unlike in the stratosphere, where the inversion is caused by absorption of radiation by ozone, in the thermosphere the inversion is a result of the extremely low density of molecules. The temperature of this layer can rise to 1,50 0 °C (2,700 °F), though the gas molecules are so far apart that temperature in the usual sense is not well defined. The air is so rarefied, that an individual molecule

(of oxygen , for example) travels an average of 1 kilometer between collisions with other molecules.
[3] The International Space
Station orbits in this layer, between 320 and 380 km (200 and 240 mi). Because of the relative infrequency of molecular collisions, air above the mesopause is poorly mixed compared to air below. While the composition from the troposphere to the mesosphere is fairly constant, above a certain point, air is poorly mixed and becomes compositionally stratified. The point dividing these two regions is known as the turbopause . The region below is the homosphere, and the region above is the heterosphere. The top of the thermosphere is the bottom of the exosphere, called the exobase . Its height varies with solar activity and ranges from about 350 –800 km (220–500 mi;
1,100,000 –2,600,000 ft).
[ edit ]Mesosphere
Main article: Mesosphere
The mesosphere extends from the stratopause to 80
–85 km (50–53 mi; 260,000–280,000 ft). It is the layer where most meteors burn up upon entering the atmosphere. Temperature decreases with height in the mesosphere. The mesopause , the temperature minimum that marks the top of the mesosphere, is the coldest plac e on Earth and has an average temperature around −85 °C (−120 °F
; 190 K ).
[4] At the mesopause , temperatures may drop to
−100 °C (−150 °F; 170 K).
[5] Due to the cold temperature of the mesosphere, water vapor is frozen, forming ice clouds (or Noctilucent clouds ). A type of lightning referred to as either sprites or ELVES , form many miles above thunderclouds in the troposphere.
[ edit ]Stratosphere
Main article: Stratosphere
The stratosphere extends from the tropopause to about 51 km (32 mi; 170,000 ft). Temperature increases with height due to increased absorption of ultraviolet radiation by the ozone layer , which restricts turbulence and mixing. While the temperature may be
−60
°C(−76 °F; 210 K) at the troposphere, the top of the stratosphere is much warmer, and may be near freezing [ citation needed ] .
The stratopause , which is the boundary between the stratosphere and mesosphere, typically is at 50 to 55 km (31 to 34 mi; 160,000 to
180,000 ft). The pressure here is 1/1000 sea level .
[ edit ]Troposphere
Main article: Troposphere
The troposphere begins at the surface and extends to between 9 km (30,000 ft) at the poles and 17 km (56,000 ft) at the equator, [6] with some variation due to weather. The troposphere is mostly heated by transfer of energy from the surface, so on average the lowest part of the troposphere is warmest and temperature decreases with altitude. This promotes vertical mixing (hence the origin of its name in the Greek word "τροπή", trope , meaning turn or overturn). The troposphere contains roughly 80% [ citation needed ] of the mass of the atmosphere. The tropopause is the boundary between the troposphere and stratosphere.
[ edit ] Other layers
Within the five principal layers determined by temperature are several layers determined by other properties.

The ozone layer is contained within the stratosphere. In this layer ozone concentrations are about 2 to 8 parts per million, which is much higher than in the lower atmosphere but still very small compared to the main components of the atmosphere. It is mainly located in the lower portion of the stratosphere from about 15
–35 km (9.3–22 mi; 49,000–110,000 ft), though the thickness varies seasonally and geographically. About 90% of the ozone in our atmosphere is contained in the stratosphere.


The ionosphere , the part of the atmosphere that is ionized by solar radiation, stretches from 50 to 1,000 km (31 to 620 mi; 160,000 to 3,300,000 ft) and typically overlaps both the exosphere and the thermosphere. It forms the inner edge of the magnetosphere. It has practical importance because it influences, for example, radio propagation on the Earth. It is responsible for auroras .

The homosphere and heterosphere are defined by whether the atmospheric gases are well mixed. In the homosphere the chemical composition of the atmosphere does not depend on molecular weight because the gases are mixed by turbulence.
[7] The homosphere includes the troposphere, stratosphere, and mesosphere. Above the turbopause at about 100 km (62 mi; 330,000 ft)
(essentially corresponding to the mesopause), the composition varies with altitude. This is because the distance that particles can move without colliding with one another is large compared with the size of motions that cause mixing. This allows the gases to stratify by molecular weight, with the heavier ones such as oxygen and nitrogen present only near the bottom of the heterosphere.
The upper part of the heterosphere is composed almost completely of hydrogen, the lightest element.

The planetary boundary layer is the part of the troposphere that is nearest the Earth's surface and is directly affected by it, mainly through turbulent diffusion . During the day the planetary boundary layer usually is well-mixed, while at night it becomes stably stratified with weak or intermittent mixing. The depth of the planetary boundary layer ranges from as little as about 100 m on clear, calm nights to 3000 m or more during the afternoon in dry regions.
The average temperature of the atmosphere at the surface of Earth is
14 °C (57 °F; 287 K) [8] or
15 °C (59 °F; 288 K), [9] depending on the reference.
[10] [11][12]
[ edit ]Physical properties
[ edit ] Pressure and thickness
Main article: Atmospheric pressure
The average atmospheric pressure at sea level is about 1 atmosphere (atm) = 101.3 kPa (kilopascals) = 14.7 psi (pounds per square inch) = 760 torr = 29.9 inches of mercury (symbol Hg). Total atmospheric mass is 5.1480×10 18 kg (1.135×10 19 lb), [13] about 2.5% less than would be inferred naively from the average sea level pressure and the Earth's area of 51007.2 megahectares, this portion being displaced by the Earth's mountainous terrain. Atmospheric pressure is the total weight of the air above unit area at the point where the pressure is measured. Thus air pressure varies with location and time, because the amount of air above the Earth's surface varies.
If atmospheric density were to remain constant with height the atmosphere would terminate abruptly at 8.50 km (27,900 ft). Instead, density decreases with height, dropping by 50% at an altitude of about 5.6 km (18,000 ft). As a result the pressure decrease is approximately exponential with height, so that pressure decreases by a factor of two approximately every 5.6 km (18,000 ft) and by a factor of e = 2.718… approximately every 7.64 km (25,100 ft), the latter being the average scale height of Earth's atmosphere below
70 km (43 mi; 230,000 ft). However, because of changes in temperature, average molecular weight, and gravity throughout the atmospheric column, the dependence of atmospheric pressure on altitude is modeled by separate equations for each of the layers listed above. Even in the exosphere, the atmosphere is still present. This can be seen by the effects of atmospheric drag on satellites .
In summary, the equations of pressure by altitude in the above references can be used directly to estimate atmospheric thickness.
However, the following published data are given for reference: [14]

50% of the atmosphere by mass is below an altitude of 5.6 km (18,000 ft).


90% of the atmosphere by mass is below an altitude of 16 km (52,000 ft). The common altitude of commercial airliners is about
10 km (33,000 ft) and Mt. Everest's summit is 8,848 m (29,029 ft) above sea level.

99.99997% of the atmosphere by mass is below 100 km (62 mi; 330,000 ft), although in the rarefied region above this there are auroras and other atmospheric effects. The highest X-15 plane flight in 1963 reached an altitude of 108.0 km (354,300 ft).
Weather and climate
What Is the Difference Between Weather and Climate?
It’s a sweltering midsummer day. “It must be global warming,” mutters someone. But is it the Earth’s changing climate that has made the day so warm? Or, is it just the weather that is so unbearable?
Weather is the mix of events that happen each day in our atmosphere including temperature, rainfall and humidity. Weather is not the same everywhere. Perhaps it is hot, dry and sunny today where you live, but in other parts of the world it is cloudy, raining or even snowing. Everyday, weather events are recorded and predicted by meteorologists worldwide.
Climate in your place on the globe controls the weather where you live. Climate is the average weather pattern in a place over many years. So, the climate of Antarctica is quite different than the climate of a tropical island. Hot summer days are quite typical of climates in many regions of the world, even without the affects of global warming.
Climates are changing because our Earth is warming, according to the research of scientists.
Does this contribute to a warm summer day? It may, however global climate change is actually much more complicated than that because a change in the temperature can cause changes in other weather elements such as clouds or precipitation.
What's the Difference Between Weather and Climate?
02.01.05
The difference between weather and climate is a measure of time. Weather is what conditions of the atmosphere are over a short period of time, and climate is how the atmosphere
"behaves" over relatively long periods of time.
When we talk about climate change, we talk about changes in long-term averages of daily weather. Today, children always hear stories from their parents and grandparents about how snow was always piled up to their waists as they trudged off to school. Children today in most areas of the country haven't experienced those kinds of dreadful snow-packed winters, except for the Northeastern U.S. in January 2005. The change in recent winter snows indicate that the climate has changed since their parents were young.
If summers seem hotter lately, then the recent climate may have changed. In various parts of the world, some people have even noticed that springtime comes earlier now than it did 30 years ago. An earlier springtime is indicative of a possible change in the climate.
GEOGRAPHY HALL OF FAME
Largest Continent:
Smallest Continent:
Highest Mountain:
Lowest Point on Land:
Deepest Underwater
Trench:
Largest Sea:
Geography Hall of Fame
Asia, 17,212,000 square miles
Australia, 3,132,000 square miles
Mount Everest, Himalayan Mountains, Nepal-Tibet, 29,035 feet above sea level
The Dead Sea, Israel-Jordan, water surface 1,349 feet below sea level
Mariana Trench, 200 miles southwest of Guam in the Pacific Ocean, 36,198 feet below the ocean surface
The Mediterranean Sea, 1,144,800 square miles

Highest Lake:
Lowest Lake:
The highest navigable lake is Lake Titicaca in Peru, 12,500 feet above sea level
The Dead Sea, Israel-Jordan, surface of water 1,349 feet below sea level
Largest Lake: Caspian Sea, 152,239 square miles
Largest Freshwater Lake: Lake Superior, U.S.-Canada, 31,820 square miles
Deepest Ocean:
Largest Ocean:
Smallest Ocean:
Largest Gulf:
Pacific Ocean, average depth 13,215 feet
Pacific Ocean, 60,060,700 square miles
Arctic Ocean, 5,427,000 square miles
Gulf of Mexico, 615,000 square miles
Largest Bay:
Largest Island:
The Bay of Bengal, 1,300,000 square miles
Greenland, 839,999 square miles
Largest Peninsula: Arabia, 1,250,000 square miles
Largest Archipelago:
Largest Gorge:
Longest River:
Indonesia, 3,500-mile stretch of 17,000 islands
Grand Canyon, Colorado River, Arizona, U.S., 217 miles long, 4 –18 miles wide, 1 mile deep
Deepest Gorge: Hells Canyon, Snake River, Idaho, 7,900 feet deep
Longest Mountain Range: The Andes of South America, 5,000 miles
The Nile, Africa, 4,180 miles
Shortest River: The Roe, Montana, U.S., 200 feet long
Largest River: The Amazon, South America, basin of 2,500,000 square miles
Longest Estuary: Ob River, Russia, 550 miles long, up to 50 miles wide
Largest Lagoon: Lagoa dos Patos, Brazil, 150 miles long, 4,500 square miles
Largest Waterfall: Angel Falls, Venezuela, 3,212 feet high
An archipelago is a string of islands.