Difference between revisions 1875257 and 1939582 on enwikiversity

[[Image:Ice cap.jpg|thumb|right|250px|This is an aerial image of the ice cap on Ellesmere Island, Canada. Credit: National Snow and Ice Data Center.]]
'''Earth''' is a rocky astronomical object, a liquid object, a gaseous object, and a plasma object.
{{clear}}

==Astronomy==
{{main|Draft:Astronomy}}
[[Image:Greenland 42.74746W 71.57394N.jpg|thumb|right|250px|Satellite composite image shows the ice sheet of Greenland. Credit: NASA.]]
(contracted; show full)
(b) has sufficient mass for its self-gravity to overcome rigid body forces so that it assumes a hydrostatic equilibrium (nearly round) shape, and

(c) has cleared the neighbourhood around its orbit" is called a '''planet'''.<ref name=Christensen>{{ cite book
|author=Lars Lindberg Christensen
|title=IAU 2006 General Assembly: Result of the IAU Resolution votes
|publisher=International Astronomical Union
|
monthdate=August 24,⏎
|year=  2006
|url=http://www.iau.org/public_press/news/detail/iau0603/
|accessdate=2011-10-30 }}</ref>

The proposed more general definition for a planet in orbit around another star substitutes "a star" for "the Sun" in part (a), keeps part (b), does not contain part (c), and adds "is neither a star nor a satellite of a planet."<ref name=Christensen1>{{ cite book
|author=Lars Lindberg Christensen
|title=The IAU draft definition of "planet" and "plutons"
|publisher=International Astronomical Union
|monthdate=August 16,⏎
|year=  2006
|url=http://www.iau.org/public_press/news/detail/iau0601/
|accessdate=2011-10-30 }}</ref>
{{clear}}

==Theoretical Earth==

'''Def.''' the "third planet in order from the Sun, upon which humans live"<ref name=EarthWikt>{{ cite book
|author=[[wikt:User:24.77.96.119|24.77.96.119]]
|title=Earth
|publisher=Wikimedia Foundation, Inc
|location=San Francisco, California
|monthdate=11 November⏎
|year=  2005
|url=https://en.wiktionary.org/wiki/Earth
|accessdate=2016-02-06 }}</ref> is called '''Earth'''.

==Geognosy==
{{main|Earth/Geognosy|Geognosy}}
[[Image:Slice_earth.svg|thumb|250px|right|This diagram is a theoretical interior for the rocky object called the [[Earth]] by its hominid inhabitants. Credit: [[commons:User:Dake|Dake]].]]
(contracted; show full)==Inner cores==
{{main|Earth/Cores/Inners|Inner cores}}
We know that the Earth's core is composed of an alloy of iron and other minerals.<ref name=Poirier>{{ cite book
  |author = Jean-Paul Poirier
  |title = Introduction to the Physics of the Earth's Interior
  |series = Cambridge Topics in Mineral Physics & Chemistry
  |publisher = Cambridge University Press
  |
yeardate = 2000
  |isbn = 0-521-66313-X }}</ref>

"A PKJKP [P wave, traversing the outer core K, and the inner core J, to emerge again as the P wave] traverses the inner core as a shear wave, so this is the direct evidence that the inner core is solid, because only in the solid material the shear wave can exist. In the liquid material, say water, only the compressional wave can travel through."<ref name=Cao>{{ cite book
|author=Aimin Cao
|title=Finally, a Solid Look at Earth's Core
|publisher=Live Science
|location=
|monthdate=April 14,⏎
|year=  2005
|url=http://www.livescience.com/6980-finally-solid-earth-core.html
|accessdate=2013-05-14 }}</ref>

Studying "archived data from about 20 large earthquakes, all monitored by an array of German seismic detectors back in the 1980s and '90s" has "reliably detected" a PKJKP wave in 2005, demonstrating that the inner core is solid.<ref name=Britt>{{ cite book
|author=Robert Roy Britt
|title=Finally, a Solid Look at Earth's Core
|publisher=Live Science
|location=
|monthdate=April 14,⏎
|year=  2005
|url=http://www.livescience.com/6980-finally-solid-earth-core.html
|accessdate=2013-05-14 }}</ref>

The inner core, however, is solid because of the enormous pressure.<ref name=Lowrie>{{cite book
|last = Lowrie
|first = William
|title = Fundamentals of Geophysics
|publisher = Cambridge University Press
|yeardate = 2004
|isbn=0-521-46164-2 }}</ref>

The inner core "is a solid ball of superhot iron and nickel alloy about 760 miles (1,220 kilometers) in diameter. ... the inner core is, at 10,800 degrees Fahrenheit (6,000 degrees Celsius), as hot as the surface of the sun."<ref name=Choi/>

"We know the Earth's inner core is composed mostly of iron".<ref name=Gleason>{{ cite book
|author=Arianna Gleason
|title=Earth's Rotating Inner Core Shifts Its Speed
|publisher=Yahoo! News
|location=
|monthdate=May 13,⏎
|year=  2013
|url=http://news.yahoo.com/earths-rotating-inner-core-shifts-speed-184844196.html
|accessdate=2013-05-14 }}</ref>

"The metal [iron] was subjected to more than 200 billion pascals of pressure".<ref name=Choi/>

"[M]aterial within Earth's inner core is apparently distributed in a lopsided way ... The weakness of iron might lead crystallites in the inner core to flow and line up a certain way".<ref name=Choi/>

"[T]he speed at which the inner core spun apparently fluctuated over the course of approximately decades between 1961 and 2007."<ref name=Choi>{{ cite book
|author=Charles Q. Choi
|title=Earth's Rotating Inner Core Shifts Its Speed
|publisher=Yahoo! News
|location=
|monthdate=May 13,⏎
|year=  2013
|url=http://news.yahoo.com/earths-rotating-inner-core-shifts-speed-184844196.html
|accessdate=2013-05-14 }}</ref>

"As the inner core cools, crystallizing iron releases impurities, sending lighter molten material into the liquid outer core. This upwelling, combined with the Earth's rotation, drives convection, forcing the molten metal into whirling vortices. These vortices stretch and twist magnetic field lines, creating Earth’s magnetic field. Currently, the center of the field, called an axis, emerges in the Arctic Ocean west of Ellesmere Island, about 300 miles (500 kilometers) from the geographic North Pole."<ref name=Oskin>{{ cite book
|author=Becky Oskin
|title=Why Earth's Magnetic Field Is Wonky
|publisher=LiveScience
|location=
|monthdate=July 18,⏎
|year=  2012
|url=http://www.livescience.com/21668-why-earth-magnetic-field-wonky.html
|accessdate=2013-05-14 }}</ref>

"In the last decade, seismic waves from earthquakes revealed the inner core looks like a navel orange, bulging slightly more on its western half. Geoscientists recently explained the asymmetry by proposing a convective loop: The inner core might be crystallizing on one half and melting on the other."<ref name=Oskin/>

"The lopsided growth of the inner core makes convection in the outer core a little bit lopsided, and that then induces the geomagnetic field to have this lopsided or eccentric character too".<ref name=Olson>{{ cite book
|author=Peter Olson
|title=Why Earth's Magnetic Field Is Wonky
|publisher=LiveScience
|location=
|monthdate=July 18,⏎
|year=  2012
|url=http://www.livescience.com/21668-why-earth-magnetic-field-wonky.html
|accessdate=2013-05-14 }}</ref>

"Magnetic particles trapped and aligned in rocks reveal that the magnetic north pole wandered around the Western Hemisphere over the past 10,000 years, and circled the Eastern Hemisphere before that — a result mirrored by the numerical test."<ref name=Oskin/>

"The key question for interesting ideas like translational instability is, 'Can we test it?' ... What we're doing is proposing a test, and we think it's a good test because people can go out and look for eccentricity in the rock record and that will either confirm or shoot down this idea."<ref name=Olson/>

"Within less than 100 million years, everything that has been crystallized on the west will have melted on the east"<ref name=Alboussiere>{{ cite book
|author=Thierry Alboussiere
|title=Earth's Inner Core Might Be on the Move
|publisher=Live Science
|location=
|monthdate=August 4,⏎
|year=  2010
|url=http://www.livescience.com/8409-earth-core-move.html
|accessdate=2013-05-14 }}</ref>

Seismic "waves appear to travel faster through the inner core from north to south than from west to east. Seismic properties also seemed to vary between the Eastern and Western hemispheres of the globe."<ref name=Peeples>{{ cite book
|author=Lynne Peeples
|title=Earth's Inner Core Might Be on the Move
|publisher=Live Science
|location=
|monthdate=August 4,⏎
|year=  2010
|url=http://www.livescience.com/8409-earth-core-move.html
|accessdate=2013-05-14 }}</ref>

There is a "124-mile (200-km) thick layer of dense material detected on its surface."<ref name=Peeples/>

"[T]he inner core [may be] shifted slightly off-center, just to the east. This would put more pressure on the western side, where it would be closer to the center of the planet, and less pressure on the eastern side. The result could be a perpetually denser Western hemisphere and a continual flow of dense fluid from the east that eventually spreads out atop the entire inner core."<ref name=Peeples/>

"The inner core is basically regenerating itself. And superimposed on that is this overall cooling that makes the inner core bigger and bigger over time".<ref name=Bergman>{{ cite book
|author=Michael Bergman
|title=Earth's Inner Core Might Be on the Move
|publisher=Live Science
|location=
|monthdate=August 4,⏎
|year=  2010
|url=http://www.livescience.com/8409-earth-core-move.html
|accessdate=2013-05-14 }}</ref>

"It is the first observational evidence that the inner core rotates at a variety of speeds with respect to the mantle...It also reconciles old discrepancies".<ref name=Tkalcic>{{ cite book
|author=Hrvoje Tkalcic
|title=Earth's Rotating Inner Core Shifts Its Speed
|publisher=Yahoo! News
|location=
|monthdate=May 13,⏎
|year=  2013
|url=http://news.yahoo.com/earths-rotating-inner-core-shifts-speed-184844196.html
|accessdate=2013-05-14 }}</ref>

"The inner core, on average, rotates eastward. At the speeds it travels, it might, on average, complete a revolution every 750 to 1,440 years. However, these speeds appear unstable, which makes it uncertain just how long it actually takes to finish a turn on its axis".<ref name=Choi/>
{{clear}}

==Object astronomy==
(contracted; show full)
[[Image:Glacial icefall.jpg|thumb|right|250px|This is an image of icefalls on three parallel glaciers. Credit: Tom Lowell, University of Cincinnati.]]
[[Image:Glacier table.jpg|thumb|left|250px|Talefre Glacier on Mont Blanc Massif in the European Alps sported a prominent glacier table when this undated photograph was taken. Credit: Cairrar.]]
The Perseid meteor shower, a shower of 
[[rocks]] or [[Rocks/Rocky objects|rocky objects]], usually the richest meteor shower of the year, peaks in August. Over the course of an hour, a person watching a clear sky from a dark location might see as many as 50-100 meteors. Most meteors are actually pieces of rock that have broken off a comet and continue to orbit the Sun. The Earth travels through the comet debris in its orbit. As the small pieces enter the Earth's atmosphere, friction can causes them to burn up.

The lower two images on the right show slower moving objects or clouds. These move relative to objects on the ground. By theoretical definition these are also meteors, but composed of water droplets small enough to be suspended in the Earth's atmosphere. They can move horizontally or can rise or form vertically as water vapor (a gas) condenses into small liquid drops of water.

The image on the left shows two meteors, the clouds passing over land and the rain falling towards the ground from the clouds above as the water droplets either lose their static charge or reach too large a size to be held aloft either by the [[natural electric field of the Earth]] or by air currents, respectively. The water droplets are moving somewhat horizontally and also vertically.

'''Def.''' a "part of a glacier with rapid flow and a chaotic crevassed surface; occurs where the glacier bed steepens or narrows"<ref name=Beitler/> is called an '''icefall'''.

(contracted; show full)
"A NASA camera on the Deep Space Climate Observatory (DSCOVR) satellite has returned its first view of the entire sunlit side of Earth [on the right] from one million miles away."<ref name=Cole>{{ cite book
|author=Steve Cole and Rob Gutro
|title=NASA Satellite Camera Provides “EPIC” View of Earth
|publisher=NASA
|location=Washington, DC USA
|
monthdate=20 July⏎
|year=  2015
|url=http://www.nasa.gov/press-release/nasa-satellite-camera-provides-epic-view-of-earth
|accessdate=2015-12-09 }}</ref>

"The color images of Earth from NASA’s Earth Polychromatic Imaging Camera (EPIC) are generated by combining three separate images to create a photographic-quality image. The camera takes a series of 10 images using different narrowband filters -- from ultraviolet to near infrared -- to produce a variety of science products. The red, green and blue channel images are used in these Earth images."<ref name=Cole/>

"This first DSCOVR image of our planet demonstrates the unique and important benefits of Earth observation from space. As a former astronaut who’s been privileged to view the Earth from orbit, I want everyone to be able to see and appreciate our planet as an integrated, interacting system. DSCOVR’s observations of Earth, as well as its measurements and early warnings of space weather events caused by the sun, will help every person to monitor the ever-changing Earth, and to understand how our planet fits into its neighborhood in the solar system.”<ref name=Bolden>{{ cite book
|author=Charlie Bolden
|title=NASA Satellite Camera Provides “EPIC” View of Earth
|publisher=NASA
|location=Washington, DC USA
|monthdate=20 July⏎
|year=  2015
|url=http://www.nasa.gov/press-release/nasa-satellite-camera-provides-epic-view-of-earth
|accessdate=2015-12-09 }}</ref>

"These initial Earth images show the effects of sunlight scattered by air molecules, giving the images a characteristic bluish tint."<ref name=Cole/>

"The images clearly show desert sand structures, river systems and complex cloud patterns."<ref name=Szabo>{{ cite book
|author=Adam Szabo
|title=NASA Satellite Camera Provides “EPIC” View of Earth
|publisher=NASA
|location=Washington, DC USA
|monthdate=20 July⏎
|year=  2015
|url=http://www.nasa.gov/press-release/nasa-satellite-camera-provides-epic-view-of-earth
|accessdate=2015-12-09 }}</ref>

"The primary objective of DSCOVR, a partnership between NASA, the National Oceanic and Atmospheric Administration (NOAA) and the U.S. Air Force, is to maintain the nation’s real-time solar wind monitoring capabilities, which are critical to the accuracy and lead time of space weather alerts and forecasts from NOAA."<ref name=Cole/>

(contracted; show full)
|author=Danielle Briot, Jean Schneider, and Luc arnold
|title=The terrestrial vegetation observed in the Earthshine spectrum: a test for the detectability of vegetation on extrasolar planets, In: ''Proceedings of the Conference on Towards Other Earths: DARWIN/TPF and the Search for Extrasolar Terrestrial Planets''
|publisher=European Space agency
|location=Noordwijk, Netherlands
|
monthdate=October⏎
|year=  2003
|editor=M. Fridlund, T. Henning
|pages=375-8
|url=
|isbn=92-9092-849-2
|arxiv=
|bibcode=2003ESASP.539..375B
|doi=
(contracted; show full)
[[Image:Fast ice.jpg|thumb|right|250px|This is land fast ice. Credit: Michael Van Woert, National Oceanic and Atmospheric Administration/Department of Commerce.]]
'''Def.''' "[t]he gases surrounding the Earth or any astronomical body"<ref name=AtmosphereWikt>{{ cite book
|author=[[wikt:User:212.159.113.112|212.159.113.112]]
|title=atmosphere
|publisher=Wikimedia Foundation, Inc
|location=San Francisco, California
|
monthdate=6 May⏎
|year=  2003
|url=https://en.wiktionary.org/wiki/atmosphere
|accessdate=2016-02-06 }}</ref> is called an '''atmosphere'''.

Atmospheric [[w:gas|gas]]es scatter blue light more than other wavelengths, giving the [[Earth]] a blue halo when seen from space, as shown in the image at right.

'''Def.''' "ice that is anchored to the shore or ocean bottom, typically over shallow ocean shelves at continental margins; fast ice is defined by the fact that it does not move with the winds or currents"<ref name=Beitler/> is called '''fast ice'''.

The image at the right shows land fast ice.
{{clear}}

==Cyans==
(contracted; show full)
|author=Josh Maurer and Summer Rupper
|title=A New DEM Extraction Method for Hexagon Spy Imagery and Application to Bhutan Glaciers
|publisher=DigitalCommons
|location=
|
month=
|yeardate=2014
|url=http://digitalcommons.usu.edu/cgi/viewcontent.cgi?article=1360&context=spacegrant&sei-redir=1&referer=http%3A%2F%2Fscholar.google.com%2Fscholar%3Fstart%3D30%26q%3Dcyans%2Bglaciers%2B-acetic%26hl%3Den%26as_sdt%3D0%2C3#search=%22cyans%20glaciers%20-acetic%22
|accessdate=2014-09-25 }}</ref>

(contracted; show full)
In the photograph at the right, Piz Bernina is the highest mountain of the region. Note the yellow Sahara-dust layer melting out in the mid-elevation range of the glacier.<ref name=StaffUUNL>{{ cite book
|author=StaffUUNL
|title=Location and scenery
|publisher=Institute for Marine and Atmospheric Research
|location=
|
monthdate=September⏎
|year=  2014
|url=http://www.staff.science.uu.nl/~oerle102/site_Mort/menu_1.html
|accessdate=2014-09-26 }}</ref>

"The Morteratschgletscher is located in the Bernina Alps, in the Swiss province ("Kanton") Graubuenden, close to Sankt Moritz."<ref name=StaffUUNL/>
{{clear}}

==Oranges==
(contracted; show full)
[[Image:Methane bubbles.jpe.jpeg|thumb|right|250px|Methane bubbles are trapped in lake ice in Siberia in early autumn. Credit: Katey Walter, AP/Nature.]]
"Methane trapped in a special type of permafrost [in the image at the right] is bubbling up at rate five times faster than originally measured [...]."<ref name=Borenstein>{{ cite book
|author=Seth Borenstein
|title=Scientists Find New Global Warming 'Time Bomb’
|publisher=Common Dreams News Center
|location=
|
monthdate=September 7,⏎
|year=  2007
|url=http://www.thewe.cc/weplanet/news/arctic/permafrost_melting.htm#this_is_real
|accessdate=2014-09-20 }}</ref>
{{clear}}

==Liquid objects==
{{main|Liquids/Liquid objects|Liquid objects}}
[[Image:Thermokarst lakes.jpe.jpeg|thumb|right|250px|An aerial view shows thermokarst lakes in northeast Siberia. Credit: Dmitry Solovyov/REUTERS.]]
[[Image:ThermokarstGlossary.jpg|thumb|left|250px|Increased thawing of frozen ground could create more thermokarst features, like this lake. Credit: Andrew Slater.]]
'''Def.''' "water that forms transition layers at mineral/water and mineral/water/ice interfaces in frozen ground"<ref name=Beitler/> is called '''interfacial water'''.

'''Def.''' "water occurring in unfrozen zones (taliks and cryopegs) within permafrost"<ref name=Beitler/> is called '''interpermafrost water'''.

At the right is an "aerial view [of] thermokarst lakes outside the town of Chersky in northeast Siberia [on] August 28, 2007."<ref name=Solovyov>{{ cite book
|author=Dmitry Solovyov
|title=Large increase in leakage of methane gas from the Arctic seabed
|publisher=The We at WePlanet
|location=
|monthdate=28 August⏎
|year=  2007
|url=http://www.thewe.cc/weplanet/news/arctic/permafrost_melting.htm#this_is_real
|accessdate=2014-09-20 }}</ref>

'''Def.''' "a lake occupying a closed depression formed by settlement of the ground following thawing of ice-rich permafrost or the melting of massive ice"<ref name=Beitler/> is called a '''thermokarst lake'''.

(contracted; show full)At the right is an image of yedoma.

"The shiny surface of the cliff represents massive ice wedges."<ref name=BorensteinAugust>{{ cite book
|author=Seth Borenstein
|title=Scientists Find New Global Warming 'Time Bomb’
|publisher=the We
|location=
|
monthdate=28 August⏎
|year=  2007
|url=http://www.thewe.cc/weplanet/news/arctic/permafrost_melting.htm#this_is_real
|accessdate=2014-09-20 }}</ref>

"Most of the yedoma is in little-studied areas of northern and eastern Siberia. What makes that permafrost special is that much of it lies under lakes; the carbon below gets released as methane. Carbon beneath dry permafrost is released as carbon dioxide."<ref name=BorensteinAugust/>

"The big methane or carbon dioxide release hasn’t started yet, but it’s coming."<ref name=Romanovsky>{{ cite book
|author=Vladimir Romanovsky
|title=Scientists Find New Global Warming 'Time Bomb’
|publisher=the We
|location=
|monthdate=28 August⏎
|year=  2007
|url=http://www.thewe.cc/weplanet/news/arctic/permafrost_melting.htm#this_is_real
|accessdate=2014-09-20 }}</ref>

In the image at the right, "Sergey Zimov, director of the Northeast Science Station in Siberia, [examines] a cross-section of yedoma, carbon trapped in permafrost along the bank of the Kolyma River in Siberia."<ref name=BorensteinAugust/>

(contracted; show full)
|author=Herbert Lettner, T. Wilflinger, A.K. Hubmer, P. Bossew
|title=Extreme radionuclide accumulation on alpine glaciers in cryoconites
|publisher=International Congress of the International Radiation Protection Association
|location=Buenos Aires, Argentina
|
month=19-24date=19 October⏎
|year=  2008
|editor=
|pages=1
|url=https://inis.iaea.org/search/search.aspx?orig_q=RN:42103485
|arxiv=
|bibcode=
|doi=
|pmid=
(contracted; show full)

The [[w:Earth's atmosphere|Earth's atmosphere]] is divided into altitude regions:<ref name=NWS>{{ cite book
| title=Layers of the Atmosphere
⏎
|work=, In: ''JetStream, the National Weather Service Online Weather School''
| publisher=National Weather Service
| url=http://www.srh.noaa.gov/srh/jetstream/atmos/layers.htm
| accessdate=22 December 2005 }}</ref>
* [[w:Troposphere|Troposphere]] &mdash; surface to 8,000 m at the poles &ndash; 18,000 m at the [[w:equator|equator]], ending at the Tropopause.
* [[w:Stratosphere|Stratosphere]] &mdash; Troposphere to 50 km
* [[w:Mesosphere|Mesosphere]] &mdash; Stratosphere to 85 km
* [[w:Thermosphere|Thermosphere]] &mdash; Mesosphere to 675 km
(contracted; show full)
| url= http://dictionary.oed.com/cgi/entry/50180718?query_type=word&queryword=planet
|publisher = Oxford English Dictionary
| title = planet, n.
| accessdate=
2008-02-07
|month7 February 2008
|date=December⏎
|year=  2007 }} ''Note: select the Etymology tab ''</ref><ref name=Goldstein>{{ cite journal
|author=Bernard R. Goldstein
|title=Saving the phenomena : the background to Ptolemy's planetary theory
| journal=Journal for the History of Astronomy
|volume=28
|issue=1
|year=1997
|pages=1–12
|location=Cambridge (UK) 
|bibcode=1997JHA....28....1G }}</ref><ref name=Ptolemy>{{ cite book
|title=Ptolemy's Almagest
|author= Ptolemy|coauthors= and Toomer, G. J.|publisher=Princeton University Press|yeardate=1998|isbn=9780691002606}}</ref>

"And Helios, lord of the sun, sitting Away from the other gods, sitting in his own temple And listening to prayers breathing up from men: he heard."<ref name=Raffel>{{ cite journal
|author=Burton Raffel
|title=Homeric Hymn to Demeter 1-89
|journal=Arion
|month=Winter
|year=1970
(contracted; show full)

'''Def.''' "the expanse of space that seems to be over the earth like a dome"<ref name=Gove>{{ cite book
|author=
|title=Webster's Seventh New Collegiate Dictionary
|publisher=G. & C. Merriam Company
|location=Springfield, Massachusetts
|
yeardate=1963
|editor=Philip B. Gove
|pages=1221
|bibcode=
|doi=
|pmid=
|isbn=
|accessdate=2011-08-26 }}</ref> is called the '''sky''', or the sometimes the '''heavens'''.
(contracted; show full)
[[Image:Ash and Steam Plume, Soufriere Hills Volcano, Montserrat.jpg|thumb|right|250px|This oblique astronaut photograph from the International Space Station (ISS) captures a white-to-grey volcanic ash and steam plume extending westwards from the Soufriere Hills volcano. Credit: NASA Expedition 21 crew.]]
Oblique images such as the one at right are taken by astronauts looking out from the ISS at an angle, rather than looking straight downward toward the 
[[Earth]] (a perspective called a nadir view), as is common with most remotely sensed data from satellites. An oblique view gives the scene a more three-dimension quality, and provides a look at the vertical structure of the volcanic plume. While much of the island is covered in green vegetation, grey deposits that include pyroclastic flows and volcanic mud-flows (lahars) are visible extending from the volcano toward the coastline. When compared to its extent in earlier views, the volcanic debris has filled in more (contracted; show full)

At right is a "[r]ecent airborne geophysical surveys near Decorah, Iowa [which is] providing an unprecedented look at a 470- million-year-old meteorite crater concealed beneath bedrock and sediments."<ref name=Koontz>{{ cite book
|author=Heidi Koontz and Robert McKay
|title=Iowa Meteorite Crater Confirmed
|publisher=U.S. Geological Survey
|location=12201 Sunrise Valley Dr, MS 119 Reston, Virginia 20192 USA
|
monthdate=March 5,⏎
|year=  2013
|url=http://www.usgs.gov/newsroom/article.asp?ID=3521#.UVfS467Qorc
|accessdate=2013-03-30 }}</ref>

"Capturing images of an ancient meteorite impact was a huge bonus," said Dr. Paul Bedrosian, a USGS geophysicist in Denver who is leading the effort to model the recently acquired geophysical data.<ref name=Koontz/> "These findings highlight the range of applications that these geophysical methods can address."<ref name=Koontz/>

(contracted; show full)(ASTER) on NASA’s Terra satellite shows the dramatic difference in the amount of water-covered land at the head of the southeast corner of the bay during a high tide on April 20, 2001, and a low tide on September 30, 2002. Vegetation is green, and water ranges from dark blue (deeper water) to light purple (shallow water)."<ref name=Wiscombe>{{ cite book
|author=Warren Wiscombe
|title=High and Low Tides in Bay of Fundy
|publisher=NASA Earth Observatory
|location=NASA Goddard Space Flight Center
|
monthdate=June 14,⏎
|year=  2006
|url=http://earthobservatory.nasa.gov/IOTD/view.php?id=6650
|accessdate=2012-05-27 }}</ref> Credit: NASA/GSFC/METI/ERSDAC/JAROS, and U.S./Japan ASTER Science Team.]]
[[Image:A beach in Oban - geograph.org.uk - 14019.jpg|thumb|right|250px|In Oban, U.K., the tide has gone out. Credit: Angelia Streluk.]]
In addition to the Sun, the Moon affects life forms on Earth such as those along the shores of bodies of water through the production of [[w:Tide|tide]]s.

"Due to phenomena such as ice ages, plate tectonics, land uplift, erosion and sedimentation, tides have changed dramatically over thousands of years"<ref name=Hill>{{ cite book
|author=David Hill
|title=Ancient Tides Different from Today - Some Dramatically Higher
|publisher=Oregon State University
|location=Corvallis, Oregon
|monthdate=July 29,⏎
|year=  2011
|url=http://oregonstate.edu/ua/ncs/archives/2011/jul/ancient-tides-different-today-–-some-dramatically-higher
|accessdate=2012-05-27 }}</ref>.

"Some tides on the East Coast of the United States ... may ... have [had] ... a difference between low and high tide of 10-20 feet, instead of the current 3-6 foot range."<ref name=Hill/>

(contracted; show full)lled "Northern Lights" in the Northern Hemisphere, auroras are caused by collisions between charged particles from the magnetosphere and air molecules high in the Earth's atmosphere. If viewed from space, auroras can be seen to glow in X-ray and ultraviolet light as well. Predictable auroras might occur a few days after a powerful magnetic event has been seen on the sun."<ref name=Harvey11S>{{ cite book
|author=Samantha Harvey
|title=Aurora Over Norway
|publisher=NASA
|location=
|
monthdate=September 28,⏎
|year=  2011
|url=http://solarsystem.nasa.gov/multimedia/display.cfm?Category=GreatShots&IM_ID=12648
|accessdate=2012-07-21 }}</ref>

Most aurorae occur in a band known as the ''auroral zone'',<ref name="feldstein63">{{cite journal
|year=1963
|title=Some problems concerning the morphology of auroras and magnetic disturbances at high latitudes
|journal= Geomagnetism and Aeronomy
(contracted; show full)|accessdate=2014-06-23 }}</ref>

'''Def.''' "a dome-shaped mass of glacier ice that spreads out in all directions"<ref name=Beitler>{{ cite book
|author=Jane Beitler
|title=Cryosphere Glossary
|publisher=National Snow and Ice Data Center
|location=
|
monthdate=19 September⏎
|year=  2014
|url=http://nsidc.org/cryosphere/glossary/I
|accessdate=2014-09-17 }}</ref> is called an '''ice cap'''.

An "ice cap is usually larger than an icefield but less than 50,000 square-kilometers (12 million acres)."<ref name=Beitler/>

(contracted; show full)

"Recent observations have removed from NASA's asteroid impact hazard list the near-Earth object (NEO) known to pose the most significant risk of Earth impact over the next 100 years."<ref name=Chesley>{{ cite book
|author=Steven Chesley
|title=Asteroid 2007 VK184 Eliminated as Impact Risk to Earth
|publisher=NASA/JPL
|location=Pasadena, California USA
|
monthdate=2 April⏎
|year=  2014
|url=http://neo.jpl.nasa.gov/news/news183.html
|accessdate=2015-09-02 }}</ref>

"2007 VK184, an asteroid estimated to be roughly 130 meters in size, has been on NASA's Impact Risk Page maintained by the NEO Program Office at the Jet Propulsion Laboratory (JPL) for several years, with an estimated 1-in-1800 chance of impacting Earth in June 2048. This predicted risk translates to a rating of 1 on the 10-point Torino Impact Hazard Scale. In recent months, 2007 VK184 has been the only know(contracted; show full)uld force a time-consuming search of much more of the sky. The trade-off was increased exposure time to detect such a faint, distant object. Greater atmospheric turbulence on March 26 blurred the images of the asteroid enough to make the detection questionable, but the March 27 images were much better and confirmed the recovery."<ref name=Tholen>{{ cite book
|author=David Tholen
|title=Asteroid 2007 VK184 Eliminated as Impact Risk to Earth
|publisher=NASA/JPL
|location=Pasadena, California USA
|
monthdate=2 April⏎
|year=  2014
|url=http://neo.jpl.nasa.gov/news/news183.html
|accessdate=2015-09-02 }}</ref>

"The "Sentry" asteroid monitoring system at JPL automatically retrieved the new observations of 2007 VK184 from the MPC database, updated the orbit for the object, and computed a new impact hazard assessment. This new work shows that 2007 VK184 will pass no closer than 1.9 million kilometers (1.2 million miles) from the Earth in June 2048, with no closer encounters predicted for the foreseeable future. (contracted; show full)

"Asteroid 2007 VK184 is another case study on how our system works."<ref name=Johnson>{{ cite book
|author=Lindley Johnson
|title=Asteroid 2007 VK184 Eliminated as Impact Risk to Earth
|publisher=NASA/JPL
|location=Pasadena, California USA
|
monthdate=2 April⏎
|year=  2014
|url=http://neo.jpl.nasa.gov/news/news183.html
|accessdate=2015-09-02 }}</ref>

"We find them, track them, learn as much as we can about those found to be of special interest - an impact hazard or a space mission destination - and we predict and monitor their movement in the inner solar system until we know they are of no more concern."<ref name=Johnson/>

The image at right is of asteroid 2012 LZ1 using the Arecibo Planetary Radar.

"On Sunday, June 10, a potentially hazardous asteroid thought to have been 500 meters (0.31 miles) wide was discovered by Siding Spring Observatory in New South Wales, Australia. Fortunately for us, asteroid 2012 LZ1 drifted safely by, coming within 14 lunar distances from Earth on Thursday, June 14."<ref name=Neill>{{ cite book
|author=Ian O'Neill
|title=Asteroid 2012 LZ1 Just Got Supersized
|publisher=Discovery Communications, LLC
|location=
|monthdate=June 22,⏎
|year=  2012
|url=http://news.discovery.com/space/asteroid-2012-lz1-just-got-supersized-120622.htm
|accessdate=2013-10-24 }}</ref>

"Asteroid 2012 LZ1 is actually bigger than thought… in fact, it is quite a lot bigger. 2012 LZ1 is one kilometer wide (0.62 miles), double the initial estimate."<ref name=Neill/>

Asteroid "2012 LZ1′s surface is really dark, reflecting only 2-4 percent of the light that hits it — this contributed to the underestimated initial optical observations. Looking for an asteroid the shade of charcoal isn’t easy."<ref name=Neill/>

“This object turned out to be quite a bit bigger than we expected, which shows how important radar observations can be, because we’re still learning a lot about the population of asteroids”.<ref name=Howell2012>{{ cite book
|author=Ellen Howell
|title=Asteroid 2012 LZ1 Just Got Supersized
|publisher=Discovery Communications, LLC
|location=
|monthdate=June 22,⏎
|year=  2012
|url=http://news.discovery.com/space/asteroid-2012-lz1-just-got-supersized-120622.htm
|accessdate=2013-10-24 }}</ref>

“The sensitivity of our radar has permitted us to measure this asteroid’s properties and determine that it will not impact the Earth at least in the next 750 years”.<ref name=Nolan>{{ cite book
|author=Mike Nolan
|title=Asteroid 2012 LZ1 Just Got Supersized
|publisher=Discovery Communications, LLC
|location=
|monthdate=June 22,⏎
|year=  2012
|url=http://news.discovery.com/space/asteroid-2012-lz1-just-got-supersized-120622.htm
|accessdate=2013-10-24 }}</ref>
{{clear}}

==Recent history==
{{main|History/Recent|Recent history}}
[[Image:Bergschrund.jpg|thumb|right|250px|The image from 1936 shows explorers on Skillet Glacier. Credit: Janet Beitler.]]
(contracted; show full)clay,<ref name=Millot>Georges Millot, translated [from the French] by W.R. Farrand, Helene Paquet, ''Geology Of Clays - Weathering, Sedimentology, Geochemistry'' Springer Verlag, Berlin (1970), {{ISBN|0-412-10050-9}}.</ref> and the processes that result in their deposition.<ref name=Nichols>Gary Nichols, ''Sedimentology & Stratigraphy'', Wiley-Blackwell, Malden, MA (1999), {{ISBN|0-632-03578-1}}.</ref>

Sedimentary rocks cover most of the 
[[Earth]]'s surface, record much of the Earth's history, and harbor the fossil record. Sedimentology is closely linked to stratigraphy, the study of the physical and temporal relationships between rock layers or strata.
{{clear}}

==Triassic==
{{main|History/Triassic|Triassic}}
[[Image:Triassic Utah.JPG|thumb|right|250px|This middle Triassic marginal marine sequence in southwestern Utah consists of siltstones and sandstones. Credit: [[w:User:Wilson44691|Wilson44691]].]]
(contracted; show full)
The "Stratospheric Observatory for Infrared Astronomy [(SOFIA) is] mounted onboard a Boeing 747SP. [...] SOFIA’s 2.7 m mirror and optimized telescope system combines the highest available spatial resolution with excellent sensitivity. SOFIA will operate in both celestial hemispheres for the next two decades."<ref name=Krabbe>{{ cite book
| author=Alfred Krabbe
| title=SOFIA telescope, In: ‘’Proceedings of SPIE: Astronomical Telescopes and Instrumentation’’
| pages=276–281
| date=March
, 2007
| publisher=SPIE — The International Society for Optical Engineering
| location=Munich, Germany
|url=http://arxiv.org/pdf/astro-ph/0004253v1.pdf
| arxiv=astro-ph/0004253 }}</ref>

It has an operating altitude of 12-14 km, 39,000-45,000 ft and a spatial resolution of 1-3" for 0.3 < λ < 15 µm, and λ/10" for λ > 15 µm.<ref name=Krabbe/> 
{{clear}}

==Hypotheses==
{{main|Hypotheses}}
# Earth is a rocky object throughout most of its interior and exterior.

==See also==
{{div col|colwidth=12em}}
* [[Solar System, technical/Earth]]
{{Div col end}}

==References==
{{reflist|2}}

==External links==

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