Difference between revisions 1705268 and 1812476 on enwikiversity

[[Image:Ice cap.jpg|thumb|right|200px|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|Astronomy}}
[[Image:Greenland 42.74746W 71.57394N.jpg|thumb|right|200px|Satellite composite image shows the ice sheet of Greenland. Credit: NASA.]]
(contracted; show full)
'''Def.''' "a celestial body that

(a) is in orbit around the Sun,

(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 
webbook
|author=Lars Lindberg Christensen
|title=IAU 2006 General Assembly: Result of the IAU Resolution votes
|publisher=International Astronomical Union
|month=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 webbook
|author=Lars Lindberg Christensen
|title=The IAU draft definition of "planet" and "plutons"
|publisher=International Astronomical Union
|month=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 webbook
|author=[[wikt:User:24.77.96.119|24.77.96.119]]
|title=Earth, In: ''Wiktionary''
|publisher=Wikimedia Foundation, Inc
|location=San Francisco, California
|month=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|200px|right|This diagram is a theoretical interior for the rocky object called the [[Earth]] by its hominid inhabitants. Credit: [[commons:User:Dake|Dake]].]]
[[Image:Earthquake wave paths.svg|thumb|right|200px|Seismic velocities and boundaries are diagrammed for the interior of the [[Earth]] sampled by seismic waves. Credit: .]]
[[Image:Earth-crust-cutaway-English-Large label.PNG|thumb|left|200px|This is a cutaway illustration of the interior of the [[Earth]]. Credit: Washiucho and [[commons:User:Brews ohare|Brews ohare]].]]
The diagram on the right is a theoretical interior for the Earth. Some of the depths and likely constitution of successive spheres are based on the results of [[geoseismology]]

"Evidence from [[seismology]], heat flow at the surface, and [[mineral physics]] is combined with the Earth's mass and moment of inertia to infer models of the Earth's interior - its composition, density, temperature, pressure. For example, the Earth's mean specific gravity (5.515) is far higher than the typical specific gravity of rocks at the surface (2.7&ndash;3.3), implying that the deeper material is denser. This is also implied by its low moment of inertia (0.33 ''M'' ''R''</var><sup>2</sup>, compared to 0.4 ''M'' ''R''</var><sup>2</sup> for a sphere of constant density). However, some of the density increase is compression under the enormous pressures inside the Earth. The effect of pressure can be calculated using the Adams–Williamson equation. The conclusion is that pressure alone cannot account for the increase in density."<ref name=Geophysics>{{ cite web
|title=Geophysics, In: ''Wikipedia''
|publisher=Wikimedia Foundation, Inc
|location=San Francisco, California
|month=October 18,
|year=2012
|url=http://en.wikipedia.org/wiki/Geophysics
|accessdate=2012-11-16 }}</ref>

"⏎
⏎
⏎
⏎
Reconstruction of seismic reflections in the deep interior indicate some major discontinuities in seismic velocities that demarcate the major zones of the Earth: inner core, outer core, mantle, lithosphere and crust."<ref name=Geophysics/>

"The seismic model of the Earth does not by itself determine the composition of the layers. For a complete model of the Earth, mineral physics is needed to interpret seismic velocities in terms of composition. The mineral properties are temperature-dependent, so the geotherm must also be determined. This requires physical theory for thermal conduction and convection and the heat contribution of [radionuclides] radioactive elements. The main model for the radial structure of the interior of the Earth is the Preliminary Reference Earth Model (PREM). Some parts of this model have been updated by recent findings in mineral physics (see post-perovskite) and supplemented by seismic tomography."<ref name=Geophysics/>
{{clear}}

==Crusts==
{{main|Earth/Crusts|Crusts}}
[[Image:San Andreas.jpg|thumb|right|200px|The image shows a portion of the San Andreas Fault in California USA on Earth. Credit: Robert E. Wallace, USGS.]]
Using [[airborne astronomy]], the image on the right shows a portion of the San Andreas Fault in California USA.
{{clear}}

==Cryospheres==
{{main|Earth/Cryospheres|Cryospheres}}
[[Image:Ridging 0.jpg|thumb|right|200px|The photo shows ridged sea ice. Credit: Don Perovich, U.S. Army Cold Regions Research and Engineering Laboratory.]]
[[Image:Cryosphere Fuller Projection.png|thumb|center|400px|Overview of the Cryosphere and its larger components, from the [http://maps.grida.no/go/graphic/cryosphere UN Environment Programme Global Outlook for Ice and Snow]. Credit: .]]
[[Image:Antarctica 6400px from Blue Marble.jpg|thumb|right|200px|A satellite composite image shows the ice sheet of Antarctica Credit: [[commons:User:Dave Pape|Dave Pape]].]]
"The '''cryosphere''' ... is [a]is a term which collectively describes the portions of [an astronomical object's] surface where [[water]] is in solid form, including sea ice, lake ice, river ice, snow cover, [[glaciers]], ice caps and ice sheets, and frozen ground (which includes permafrost). Thus there [may be] a wide overlap with [a] hydrosphere. The cryosphere is an integral part of the global climate system with important linkages and [[feedback]]s generated through its influence on surface energy and moisture fluxes, clouds, precipitation, [[hydrology]], atmospheric and oceanic circulation. Through these feedback processes, the cryosphere plays a significant role in global climate and in [any] climate model response to global change."<ref name=Cryosphere>{{ cite web
|title=Cryosphere, In: ''Wikipedia''
|publisher=Wikimedia Foundation, Inc
|location=San Francisco, California
|month=June 15,
|year=2013
|url=http://en.wikipedia.org/wiki/Cryosphere
|accessdate=2013-06-23 }}</ref>

"⏎
⏎
⏎
⏎
The only current ice sheets are in Antarctica and [[Greenland]]; during the last glacial period at Last Glacial Maximum (LGM) the Laurentide ice sheet covered much of North America, the Weichselian ice sheet covered northern Europe and the Patagonian Ice Sheet covered southern South America."<ref name=IceSheet>{{ cite web
|title=Ice sheet, In: ''Wikipedia''
|publisher=Wikimedia Foundation, Inc
|location=San Francisco, California
|month=June 6,
|year=2013
|url=http://en.wikipedia.org/wiki/Ice_sheet
|accessdate=2013-06-23 }}</ref>
{{clear}}

==Lithospheres==
{{main|Earth/Lithospheres|Lithospheres}}
"Between the crust and the mantle is the Mohorovičić discontinuity.<ref name=Lowrie/>"<ref name=Geophysics/>

==Mantles==
{{main|Earth/Mantles|Mantles}}
"The mantle is mainly composed of [[silicates]], and the boundaries between layers of the mantle are consistent with phase transitions.<ref name=Poirier/>"<ref name=Geophysics/>

"The mantle acts as a solid for seismic waves, but under high pressures and temperatures it deforms so that over millions of years it acts like a liquid. This makes plate tectonics possible. [[Geodynamics]] is the study of the fluid flow in the mantle and core."<ref name=Geophysics/>

"The mantle itself is divided into the upper mantle, transition zone, lower mantle and ''D′′'' layer."<ref name=Geophysics/>

==Outer cores==
{{main|Earth/Cores/Outers|Outer cores}}
"Reconstructions of seismic waves in the deep interior of the Earth show that there are no S-waves in the outer core. This indicates that the outer core is liquid, because liquids cannot support shear. The outer core is liquid, and the motion of this highly conductive fluid generates the Earth's field (see [[geodynamo]])."<ref name=Geophysics/>

==Inner cores==
{{main|Earth/Cores/Inners|Inner cores}}
"[W]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
  |year = 2000
  |isbn = 0-521-66313-X }}</ref>"<ref name=Geophysics/>

"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 webbook
|author=Aimin Cao
|title=Finally, a Solid Look at Earth's Core
|publisher=Live Science
|location=
|month=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 webbook
|author=Robert Roy Britt
|title=Finally, a Solid Look at Earth's Core
|publisher=Live Science
|location=
|month=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
|year = 2004
|isbn=0-521-46164-2 }}</ref>"<ref name=Geophysics/>

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 webbook
|author=Arianna Gleason
|title=Earth's Rotating Inner Core Shifts Its Speed
|publisher=Yahoo! News
|location=
|month=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 webbook
|author=Charles Q. Choi
|title=Earth's Rotating Inner Core Shifts Its Speed
|publisher=Yahoo! News
|location=
|month=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 webbook
|author=Becky Oskin
|title=Why Earth's Magnetic Field Is Wonky
|publisher=LiveScience
|location=
|month=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 webbook
|author=Peter Olson
|title=Why Earth's Magnetic Field Is Wonky
|publisher=LiveScience
|location=
|month=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 webbook
|author=Thierry Alboussiere
|title=Earth's Inner Core Might Be on the Move
|publisher=Live Science
|location=
|month=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 webbook
|author=Lynne Peeples
|title=Earth's Inner Core Might Be on the Move
|publisher=Live Science
|location=
|month=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 webbook
|author=Michael Bergman
|title=Earth's Inner Core Might Be on the Move
|publisher=Live Science
|location=
|month=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 webbook
|author=Hrvoje Tkalcic
|title=Earth's Rotating Inner Core Shifts Its Speed
|publisher=Yahoo! News
|location=
|month=May 13,
|year=2013
|url=http://news.yahoo.com/earths-rotating-inner-core-shifts-speed-184844196.html
(contracted; show full)
[[Image:Cirque.jpg|thumb|right|200px|This show a cirque on Cirque Mountain in the Torngat Mountains, Newfoundland, Canada. Credit: Hazen Russel, Natural Resources Canada, Terrain Sciences Division, Geological Survey of Canada.]]
"[P]referential absorption of sunlight by ozone over long horizon paths gives the zenith sky its blueness when the sun is near the horizon".<ref name=Bohren>{{ cite 
webbook
|url=http://homepages.wmich.edu/%7Ekorista/atmospheric_optics.pdf
|title=Atmospheric Optics
|author=Craig F. Bohren }}</ref>

'''Def.''' a "bowl shape or amphitheater usually sculpted out of the mountain terrain by a ... glacier"<ref name=Beitler/> is called a '''cirque'''.

The image at the right shows a cirque "on Cirque Mountain in the Torngat Mountains, Newfoundland, Canada."<ref name=Beitler/>
(contracted; show full)

When the glacier table top strikes the Earth with the melting of the pedestal, is the rock a meteorite?
{{clear}}

==Gamma rays==
{{main|Radiation astronomy/Gamma rays|Gamma-ray astronomy}}


"[T]The Earth's atmosphere ... is a relatively bright source of gamma rays produced in interactions of ordinary cosmic ray protons with air atoms"<ref name=Explorer11>{{ cite web
|title=Explorer 11, In: ''Wikipedia''
|publisher=Wikimedia Foundation, Inc
|location=San Francisco, California
|month=15 February
|year=2014
|url=https://en.wikipedia.org/wiki/Explorer_11
|accessdate=2014-02-15 }}</ref>.

==X-rays==
{{main|Radiation astronomy/X-rays|X-rays}}
[[Image:Earthxray polar.jpg|thumb|left|200px|This image is a composite of the first picture of the Earth in X-rays over a diagram of the Earth below. Credit: NASA, Ruth Netting.]]
[[Image:X-ray radiograph.jpg|thumb|right|200px|This shows a photograph and X-radiograph of part of core D4 illustrating fine laminations. Credit: Robert Gilbert, Niels Nielsen, Henrik Möller, Joseph R. Desloges, and Morten Rasch.]]
(contracted; show full)
[[Image:Spectral reflectance curves.jpg|thumb|left|200px|The figure contains spectral reflectance curves for snow and ice in different formation stages. Credit: Jan-Gunnar Winther.]]
"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 
webbook
|author=Steve Cole and Rob Gutro
|title=NASA Satellite Camera Provides “EPIC” View of Earth
|publisher=NASA
|location=Washington, DC USA
|month=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 webbook
|author=Charlie Bolden
|title=NASA Satellite Camera Provides “EPIC” View of Earth
|publisher=NASA
|location=Washington, DC USA
|month=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 webbook
|author=Adam Szabo
|title=NASA Satellite Camera Provides “EPIC” View of Earth
|publisher=NASA
|location=Washington, DC USA
|month=20 July
|year=2015
|url=http://www.nasa.gov/press-release/nasa-satellite-camera-provides-epic-view-of-earth
(contracted; show full)
[[Image:Holmengrå2.JPG|thumb|right|200px|The Earth can have a blue sky and a blue ocean. Credit: [[commons:User:Frokor|Frokor]].]]
[[Image:Fast ice.jpg|thumb|right|200px|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 
webbook
|author=[[wikt:User:212.159.113.112|212.159.113.112]]
|title=atmosphere, In: ''Wiktionary''
|publisher=Wikimedia Foundation, Inc
|location=San Francisco, California
|month=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.”<ref name=Atmosphere>{{ cite web
|title=Atmosphere, In: ''Wikipedia''
|publisher=Wikimedia Foundation, Inc
|location=San Francisco, California
|month=15 february
|year=2014
|url=https://en.wikipedia.org/wiki/Atmosphere
|accessdate=2014-02-15 }}</ref>, 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)3D visualizations in flight simulators [...] for land-change studies [there] is [...] DEM differencing [...], which compares DEMs over the same region from different time periods [like the 3D image at the right over Bhutan]. This allows quantification of surface elevation changes due to erosion, landslides, earthquakes, melting glaciers, construction of man-made features, and many other factors. It follows that historical DEMs are useful for land-surface change studies."<ref name=Maurer>{{ cite 
webbook
|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=
|year=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
(contracted; show full)
{{clear}}

==Yellows==
{{main|Radiation astronomy/Yellows|Yellow astronomy}}
[[Image:Glider.jpg|thumb|right|200px|Photo of the glacier basin taken from a glider shows the yellow Sahara-dust layer melting out in the mid-elevation range of the glacier. Credit: Christina Rothenbühler.]]
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 
webbook
|author=StaffUUNL
|title=Location and scenery
|publisher=Institute for Marine and Atmospheric Research
|location=
|month=September
|year=2014
|url=http://www.staff.science.uu.nl/~oerle102/site_Mort/menu_1.html
(contracted; show full)dentifies melt approximately up to two weeks more than the PM at higher elevation in the percolation zone toward the dry snow zone [the figure at the lower left]. Both methods (active and passive microwave) consistently identify melt areas that have a melt duration of at least 10–14 days. The longer snowmelt duration can be sufficient to decrease surface albedo and affect surface heat and mass balance."<ref name=Steffen/>
{{clear}}

==Radars==
{{main|Radiation astronomy/Radars|Radar astronomy}}

"[N]Numerous airborne and spacecraft radars have mapped the entire planet, for various purposes. One example is the Shuttle Radar Topography Mission, which mapped the entire [[Earth]] at 30 m resolution."<ref name=RadarAstronomy>{{ cite web
|title=Radar astronomy, In: ''Wikipedia''
|publisher=Wikimedia Foundation, Inc
|location=San Francisco, California
|month=July 30,
|year=2012
|url=http://en.wikipedia.org/wiki/Radar_astronomy
|accessdate=2012-08-30 }}</ref>

==Gaseous objects==
{{main|Gases/Gaseous objects|Gaseous objects}}
[[Image:Methane bubbles.jpe.jpeg|thumb|right|200px|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 webbook
|author=Seth Borenstein
|title=Scientists Find New Global Warming 'Time Bomb’
|publisher=Common Dreams News Center
|location=
|month=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|200px|An aerial view shows thermokarst lakes in northeast Siberia. Credit: Dmitry Solovyov/REUTERS.]]
[[Image:ThermokarstGlossary.jpg|thumb|left|200px|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 webbook
|author=Dmitry Solovyov
|title=Large increase in leakage of methane gas from the Arctic seabed
|publisher=The We at WePlanet
|location=
|month=28 August
|year=2007
|url=http://www.thewe.cc/weplanet/news/arctic/permafrost_melting.htm#this_is_real
(contracted; show full)
[[Image:Glacial erratic Canada.jpg|thumb|right|200px|A sense of the size of the glacial erratic can be estimated by noting the person standing in front of the boulder, on the left side. Credit: Lynda Dredge, Natural Resources Canada, Terrain Sciences Division, Geological Survey of Canada.]]
[[Image:Glacial erratic.jpg|thumb|left|Glacial erratic (granite) is in the Polish Geological Institute, Warsaw. Credit: Robert Niedźwiedzki.]]

"'''Sin-Kamen''' ({{lang|ru|Синь-Камень}}, in Russian literally – '''Blue Stone''', or '''Blue Rock''') is a type of pagan sacred stones, widespread in Russia, in areas historically inhabited by both Eastern Slavic (Russian), and Uralic tribes (Merya, Muroma<ref>[http://www.bogorodsk-noginsk.ru/atlas/sinie_kamni.html И.Д. Маланин. Материалы разведки Синих камней Подмосковья в 2003 году // Краеведение и регионоведение. Межвузовский сборник научных трудов. ч.1. Владимир, 2004.] (Russian)</ref>)."<ref name=BlueStoneRussia>{{ cite web
|title=Blue Stone (Russia), In: ''Wikipedia''
|publisher=Wikimedia Foundation, Inc
|location=San Francisco, California
|month=March 20,
|year=2013
|url=http://en.wikipedia.org/wiki/Blue_Stone_(Russia)
|accessdate=2013-05-31 }}</ref>

"⏎
⏎
⏎
⏎
While in the majority of cases, the stones belonging to the ''Blue Stones'' type, have a black, or dark gray color, this particular stone [in the image] does indeed look dark blue, when wet.<ref name="berdnikov">[http://pki.botik.ru/dl.php?b=articles&a=n-sinii1985berd.pdf Бердников,&nbsp;В. Синий камень Плещеева озера] // Наука и жизнь. – 1985. – № 1. – С.&nbsp;134–139. (Russian)</ref>"<ref name=BlueStoneRussia/>

'''Def.''' "a mass of rock fragments and finer material, on a slope, that contains either an ice core or interstitial ice, and shows evidence of past, but not present, movement"<ref name=Beitler/> is called an '''inactive rock glacier'''.

(contracted; show full)
{{clear}}

==Carbons==
{{main|Chemicals/Carbons|Carbons}}
[[Image:Yedoma carbon.jpe.jpeg|thumb|right|200px|Here, carbon is trapped in permafrost. Credit: Katey Walter.]]
At the right is an image of yedoma.

"The shiny surface of the cliff represents massive ice wedges."<ref name=BorensteinAugust>{{ cite 
webbook
|author=Seth Borenstein
|title=Scientists Find New Global Warming 'Time Bomb’
|publisher=the We
|location=
|month=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 webbook
|author=Vladimir Romanovsky
|title=Scientists Find New Global Warming 'Time Bomb’
|publisher=the We
|location=
|month=28 August
|year=2007
|url=http://www.thewe.cc/weplanet/news/arctic/permafrost_melting.htm#this_is_real
(contracted; show full)
'''Def.''' "[a] [[wikt:metallic|metallic]] or [[wikt:stony|stony]] object that is the remains of a [[wikt:meteor|meteor]]", from Wiktionary [[wikt:meteorite|meteorite]], is called a '''meteorite'''.

Many of the meteorites that are found on [[Earth]] turn out to be from other solar system objects: the Moon and Mars, for example.


"'''Widmanstätten patterns''', also called '''Thomson structures''', are unique figures of long [[w:nickel|nickel]]-[[w:iron|iron]] crystals, found in the [[w:octahedrite|octahedrite]] [[w:iron meteorite|iron meteorite]]s and some [[w:pallasite|pallasite]]s. They consist of a fine interleaving of [[w:kamacite|kamacite]] and [[w:taenite|taenite]] bands or ribbons called ''lamellæ''. Commonly, in gaps between the lamellæ, a fine-grained mixture of kamacite and taenite called [[w:plessite|plessite]] can be found."<ref name=WidmanstattenPattern>{{ cite web
|title=Widmanstätten pattern, In: ''Wikipedia''
|publisher=Wikimedia Foundation, Inc
|location=San Francisco, California
|month=15 February
|year=2014
|url=https://en.wikipedia.org/wiki/Widmanstätten_pattern
|accessdate=2014-02-15 }}</ref>

'''Def.''' a "mass of snow which becomes detached and slides down a slope, often acquiring great bulk by fresh addition as it descends"<ref name=Beitler/> is called an '''avalanche'''.
{{clear}}

==Micrometeorites==
{{main|Rocks/Micrometeorites|Micrometeorites}}
[[Image:Micrometeorite.jpg|thumb|right|200px|This is a micrometerorite collected from the antarctic snow. Credit: NASA.]]
(contracted; show full)om]]s of [[w:Chemical element|chemical element]]s. At your geographical location, specified in [[w:Geographic coordinate system|latitude and longitude]], this [[w:Gas|gaseous]] envelope extends upward. The [[w:Atmosphere of Earth|atmosphere of Earth]] changes with altitude. At high enough altitude the composition changes significantly, as does the temperature and [[w:pressure|pressure]].

The [[w:Earth's atmosphere|Earth's atmosphere]] is divided into altitude regions:<ref name=NWS>{{ cite 
webbook
| title=Layers of the Atmosphere
|work=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
(contracted; show full)

==Sun==
{{main|Stars/Sun|Sun (star)}}
[[Image:Sun rise in Kodachadri.JPG|thumb|right|200px|The image shows a sunrise in Kodachadri. Credit: [[commons:User:Chinmayahd|Chinmayahd]].]]
[[Image:Orange Sun in Boracay, Philippines.jpg|thumb|left|200px|The image shows an orange sun in Boracay, Philippines. Credit: [[commons:User:Sarahr|Sarahr]].]]
The Sun passes overhead every day on Earth. The size of its disc is very close to that of the Moon.


"Regarding the fixed stars, the Sun appears from Earth to revolve once a year along the [[w:ecliptic|ecliptic]] through the zodiac, and so Greek astronomers considered it to be one of the seven [[w:planet|planet]]s (Greek ''planetes'', "wanderer"), after which the seven days of the [[w:week|week]] are named in some languages.<ref name=oed>{{ cite webbook
| url= http://dictionary.oed.com/cgi/entry/50180718?query_type=word&queryword=planet
|publisher = Oxford English Dictionary
| title = planet, n.
| accessdate=2008-02-07
|month=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=harv }}</ref><ref name=Ptolemy>{{ cite book
|title=Ptolemy's Almagest
|author= Ptolemy|coauthors=Toomer, G. J.|publisher=Princeton University Press|year=1998|isbn=9780691002606}}</ref>"<ref name=Sun>{{ cite web
|title=Sun, In: ''Wikipedia''
|publisher=Wikimedia Foundation, Inc
|location=San Francisco, California
|month=15 February
|year=2014
|url=https://en.wikipedia.org/wiki/Sun
|accessdate=2014-02-15 }}</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)

In the image at left is an aerial view of the Barringer Meteor Crater about 69 km east of Flagstaff, Arizona USA. Although similar to the aerial view of the Soudan crater, the Barringer Meteor Crater appears angular at the farthest ends rather than round.

* Buried craters can be identified through drill coring, aerial electromagnetic resistivity imaging, and airborne gravity gradiometry.<ref name=USGS>{{ cite 
webbook
|author=US Geological Survey
|title=Iowa Meteorite Crater Confirmed
|url=http://www.usgs.gov/newsroom/article.asp?ID=3521|accessdate=7 March 2013 }}</ref>

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 webbook
|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
|month=March 5,
|year=2013
|url=http://www.usgs.gov/newsroom/article.asp?ID=3521#.UVfS467Qorc
(contracted; show full)age:Fundy High & Low tide.jpg|thumb|left|200px|"This pair of images from the Advanced Spaceborne Thermal Emission and Reflection Radiometer (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 
webbook
|author=Warren Wiscombe
|title=High and Low Tides in Bay of Fundy
|publisher=NASA Earth Observatory
|location=NASA Goddard Space Flight Center
|month=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|200px|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 webbook
|author=David Hill
|title=Ancient Tides Different from Today - Some Dramatically Higher
|publisher=Oregon State University
|location=Corvallis, Oregon
|month=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/>

"The [[w:Guinness Book of World Records|Guinness Book of World Records]] (1975) declared that [[w:Burntcoat Head, Nova Scotia|Burntcoat Head, Nova Scotia]] has the highest tides in the world:"<ref name=Bayoffundy>{{ cite web
|title=Bay of Fundy, In: ''Wikipedia''
|publisher=Wikimedia Foundation, Inc
|location=San Francisco, California
|month=May 10,
|year=2012
|url=http://en.wikipedia.org/wiki/Bay_of_Fundy
|accessdate=2012-05-27 }}</ref>
<blockquote>
“The greatest tides in the world occur in the Bay of Fundy.... Burntcoat Head in the Minas Basin, Nova Scotia, has the greatest mean spring range with 14.5 metres (47.5 feet) and an extreme range of 16.3 metres (53.5 feet).”</blockquote>

But they "didn’t amount to much at all about 5,000 years ago. ... [A]round that same time, tides on the southern U.S. Atlantic coast, from North Carolina to Florida, were about 75 percent higher."<ref name=Hill/>

(contracted; show full)uds, they only add light to the sky and do not block background stars from view. Called "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 
webbook
|author=Samantha Harvey
|title=Aurora Over Norway
|publisher=NASA
|location=
|month=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 |volume=3|pages= 183–192|author=Feldstein, Y. I.}}</ref><ref name="feldstein86">{{cite journal|bibcode=1986EOSTr..67..761F|author=Feldstein, Y. I. |year=1986|title= A Quarter Century with the Auroral Oval|journ(contracted; show full)(polar cap arcs<ref>{{ cite journal|author=Frank|year=1986|title= The theta aurora|journal= J. Geophys. Res.|volume= 91|issue= A3|pages= 3177–3224|doi=10.1029/JA091iA03p03177|author-separator=,|author2=L. A.|display-authors=2|last3=Gurnett|first3=D. A.|last4=Shawhan|first4=S. D.|last5=Weimer|first5=D. R.|last6=Burch|first6=J. L.|last7=Winningham|first7=J. D.|last8=Chappell|first8=C. R.|last9=Waite|first9=J. H.|bibcode=1986JGR....91.3177F}}</ref>), which are generally invisible to the naked eye.
"<ref name=AuroraAstronomy>{{ cite web
|title=Aurora (astronomy), In: ''Wikipedia''
|publisher=Wikimedia Foundation, Inc
|location=San Francisco, California
|month=July 14,
|year=2012
|url=http://en.wikipedia.org/wiki/Aurora_(astronomy)
|accessdate=2012-07-21 }}</ref>
{{clear}}

==Natural electric fields==
{{main|Charges/Interactions/Electromagnetics/Electric fields/Earth|Natural electric field of the Earth}}
[[Image:-D3- LighningStormPanorama.jpg|thumb|right|300px|This is a panorama photograph taken during a lightning storm over Bucharest, Romania. Credit: [[w:User:Catalin.Fatu|Catalin.Fatu]].]]
(contracted; show full)ions by space-based telescopes have revealed ... gamma ray emissions ... [[w:terrestrial gamma-ray flashes|terrestrial gamma-ray flashes]] (TGFs).  These observations pose a challenge to current theories of lightning, especially with the discovery of the clear signatures of [[w:antimatter|antimatter]] produced in lightning.<ref>[http://www.sciencenews.org/view/generic/id/49288/title/Signature_of_antimatter_detected_in_lightning Signature Of Antimatter Detected In Lightning - Science News]</ref>
"<ref name=Lightning>{{ cite web
|title=Lightning, In: ''Wikipedia''
|publisher=Wikimedia Foundation, Inc
|location=San Francisco, California
|month=15 February
|year=2014
|url=https://en.wikipedia.org/wiki/Lightning
|accessdate=2014-02-15 }}</ref>

"[A]⏎
⏎
A TGF [has been linked] to an individual lightning stroke occurring within 1.5&nbsp;ms of the TGF event,<ref name=Inan>U.S. Inan, S.C. Reising, G.J. Fishman, and J.M. Horack. On the association of terrestrial gamma-ray bursts with lightning and implications for sprites. ''Geophysical Research Letters'', 23(9):1017-20, May 1996. As quoted by [http://elf.gi.alaska.edu/spr20010406.html#InanUS:theatg elf.gi.alaska.edu] Retrieved 2007-03-06.</ref> proving for the first time that the TGF was of atmospheric origin and associated with lightning strikes"<ref name=Lightning/>.

The "[[w:Reuven Ramaty High Energy Solar Spectroscopic Imager|Reuven Ramaty High Energy Solar Spectroscopic Imager]] (RHESSI) spacecraft, as reported by David Smith of [[w:University of California, Santa Cruz|UC Santa Cruz]], has been observing TGFs at a much higher rate, indicating that these occur about 50 times per day globally (still a very small fraction of the total lightning on the planet). The energy levels recorded exceed 20 MeV. ... [Apparently, the] gamma radiation fountains upward from starting points at surprisingly low altitudes in thunderclouds. ... Steven Cummer, from Duke University's [[w:Edmund T. Pratt Jr. School of Engineering|Pratt School of Engineering]], said, "These are higher energy gamma rays than come from the sun. And yet here they are coming from the kind of terrestrial thunderstorm that we see here all the time." ... In 2009, [the] Fermi Gamma Ray Telescope in Earth orbit observed [an] intense burst of gamma rays corresponding to positron annihilations coming out of a storm formation. Scientists wouldn't have been surprised to see a few positrons accompanying any intense gamma ray burst, but the lightning flash detected by Fermi appeared to have produced about 100 trillion positrons. This has been reported by media in January 2011, it is an effect, never considered to happen before.<ref>http://news.nationalgeographic.com/news/2011/01/110111-thunderstorms-antimatter-beams-fermi-radiation-science-space/</ref>"<ref name=Lightning/>
{{clear}}

==Zodiacal Light==
{{main|Astronomy/Zodiacs/Lights|Zodiacal lights}}
[[Image:EZL-Faulkes.jpg|thumb|right|150px|The Zodiacal Light is over the Faulkes Telescope, Haleakala, Maui. Credit: 808caver.]]
(contracted; show full)
{{clear}}

==Foliation==
[[Image:Beach In Cornwall UK.jpg|thumb|right|200px|The image shows finely layered slate perhaps with occasional dolomite layers exposed on a beach in Cornwall, UK. Credit: [[commons:User:Si Griffiths|Si Griffiths]].]]
[[Image:Meguma3.jpg|thumb|right|200px|The image shows folds in slate and quartzite of the Meguma Group near the Ovens, Nova Scotia, Canada. Credit: [[commons:User:Rygel,_M.C.|Michael C. Rygel]].]]

"'''Slate''' is a fine-grained, foliated, homogeneous metamorphic rock derived from an original shale-type sedimentary rock composed of clay or volcanic ash through low-grade regional metamorphism. It is the finest grained foliated metamorphic rock.<ref name=Marshak>Essentials of Geology, 3rd Ed, Stephen Marshak</ref> Foliation may not correspond to the original sedimentary layering, but instead is in planes perpendicular to the direction of metamorphic compression.<ref name=Marshak/> [...] Slate is frequently grey in color, especially when seen, en masse, covering roofs. However, slate occurs in a variety of colors even from a single locality; for example, slate from North Wales can be found in many shades of grey, from pale to dark, and may also be purple, green or cyan."<ref name=Slate>{{ cite web
|title=Slate, In: ''Wikipedia''
|publisher=Wikimedia Foundation, Inc
|location=San Francisco, California
|month=October 16,
|year=2013
|url=https://en.wikipedia.org/wiki/Slate
|accessdate=2013-10-18 }}</ref>
{{clear}}

==Glaciology==
{{main|Rocks/Glaciers/Glaciology|Glaciology}}
[[Image:Taku glacier.jpg|thumb|left|200px|Taku Glacier winds through the mountains of southeastern Alaska. Credit: U. S. Navy.]]
[[Image:Receding glacier-en.svg|200px|thumb|right|The diagram illustrates the interrelationship of glaciology terms. Credit: .]]
(contracted; show full)|url=http://jgs.lyellcollection.org/content/142/3/447.short
|arxiv=
|bibcode=
|doi=10.1144/gsjgs.142.3.0447
|pmid=
|accessdate=2014-06-23 }}</ref>

'''Def.''' "a dome-shaped mass of glacier ice that spreads out in all directions"<ref name=Beitler>{{ cite 
webbook
|author=Jane Beitler
|title=Cryosphere Glossary
|publisher=National Snow and Ice Data Center
|location=
|month=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/>

'''Def.''' "a mass of glacier ice; similar to an ice cap, and usually smaller and lacking a dome-like shape; somewhat controlled by terrain"<ref name=Beitler/> is called an '''icefield'''.

The image at the left of "Kalstenius Icefield, located on Ellesmere Island, Canada, shows vast stretches of ice. The icefield produces multiple outlet glaciers that flow into a larger valley glacier. The glacier in this photograph is three miles wide."<ref name=Beitler/>
{{clear}}

==Astroglaciology==
[[Image:Vatnajökull.jpeg|thumb|200px|Vatnajökull, [[Iceland]] has an ice cap. Credit: NASA.]]
"The discoveries of water ice on the [[Moon]], [[Mars]] and [[Europa]] add an extraterrestrial component to the field, as in "astroglaciology".<ref name=Williams>{{ cite journal
|title=Annals of Glaciology
|volume=9
|page=255
|author=Richard S. Williams, Jr.
|url=http://www.igsoc.org/annals/9/igs_annals_vol09_year1987_pg254-255.pdf
|year=1987
|publisher=International Glaciological Society
|accessdate=7 February 2011}}</ref>"<ref name=Glaciology>{{ cite web
|title=Glaciology, In: ''Wikipedia''
|publisher=Wikimedia Foundation, Inc
|location=San Francisco, California
|month=March 30,
|year=2013
|url=http://en.wikipedia.org/wiki/Glaciology
|accessdate=2013-06-23 }}</ref>
{{clear}}

==Glaciers==
{{main|Rocks/Glaciers|Glaciers}}
[[Image:Piedmont glacier.jpg|thumb|right|200px|The massive lobe of Malaspina Glacier in Alaska is clearly visible in this photograph taken from a Space Shuttle flight. Credit: NASA.]]
[[Image:Branched valley glacier.jpg|thumb|right|200px|In this photograph from 1969, small glaciers flow into the larger Columbia Glacier from mountain valleys on both sides. Credit: United States Geological Survey.]]
(contracted; show full)
|pmid=
|accessdate=2011-10-06 }}</ref>

EC denotes Earth-crossing.<ref name= Michel/>

"50 % of the MB Mars-crossers [MCs] become ECs within 59.9 Myr and [this] contribution ... dominates the production of ECs".<ref name= Michel />

"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 
webbook
|author=Steven Chesley
|title=Asteroid 2007 VK184 Eliminated as Impact Risk to Earth
|publisher=NASA/JPL
|location=Pasadena, California USA
|month=2 April
|year=2014
|url=http://neo.jpl.nasa.gov/news/news183.html
(contracted; show full)o Earth and brighter in May, I made the recovery attempt in March because I didn't want the position uncertainty to grow so much that it would 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 
webbook
|author=David Tholen
|title=Asteroid 2007 VK184 Eliminated as Impact Risk to Earth
|publisher=NASA/JPL
|location=Pasadena, California USA
|month=2 April
|year=2014
|url=http://neo.jpl.nasa.gov/news/news183.html
(contracted; show full)acterizing near-Earth objects (NEOs) - asteroids and comets whose orbits periodically bring them close to Earth. The NEOO Program sponsors internal NASA and external research projects. The Jet Propulsion Laboratory (JPL) in Pasadena, California, manages a NEO Program Office for the Headquarters' NEOO Program and conducts a number of NASA-sponsored NEO projects."<ref name=Chesley/>

"Asteroid 2007 VK184 is another case study on how our system works."<ref name=Johnson>{{ cite 
webbook
|author=Lindley Johnson
|title=Asteroid 2007 VK184 Eliminated as Impact Risk to Earth
|publisher=NASA/JPL
|location=Pasadena, California USA
|month=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 webbook
|author=Ian O'Neill
|title=Asteroid 2012 LZ1 Just Got Supersized
|publisher=Discovery Communications, LLC
|location=
|month=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 webbook
|author=Ellen Howell
|title=Asteroid 2012 LZ1 Just Got Supersized
|publisher=Discovery Communications, LLC
|location=
|month=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 webbook
|author=Mike Nolan
|title=Asteroid 2012 LZ1 Just Got Supersized
|publisher=Discovery Communications, LLC
|location=
|month=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|200px|The image from 1936 shows explorers on Skillet Glacier. Credit: Janet Beitler.]]
The '''recent history''' period dates from around 1,000 b2k to present.

'''Def.''' a "crevasse that separates flowing ice from stagnant ice at the head of a glacier"<ref name=Beitler/> is called '''bergschrund'''.

The image at the right from 1936 shows explorers on Skillet Glacier. "Bergschrund is visible as the dark band of ice in the background."<ref name=Beitler/>

"'''Sedimentology''' encompasses the study of modern sediments such as sand,<ref name=Siever>Raymond Siever, ''Sand'', Scientific American Library, New York (1988), {{ISBN|0-7167-5021-X}}.</ref> mud (silt),<ref name=Potter>P.E. Potter, J.B. Maynard, and P.J. Depetris, ''Mud and Mudstones: Introduction and Overview'' Springer, Berlin (2005) {{ISBN|3-540-22157-3}}.</ref> and 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>"<ref name=Sedimentology>{{ cite web
|title=Sedimentology, In: ''Wikipedia''
|publisher=Wikimedia Foundation, Inc
|location=San Francisco, California
|month=March 24,
|year=2012
|url=http://en.wikipedia.org/wiki/Sedimentology
|accessdate=2012-05-23 }}</ref>

"⏎
⏎
⏎
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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."<ref name=Sedimentology/>
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==Triassic==
{{main|History/Triassic|Triassic}}
[[Image:Triassic Utah.JPG|thumb|right|200px|This middle Triassic marginal marine sequence in southwestern Utah consists of siltstones and sandstones. Credit: [[w:User:Wilson44691|Wilson44691]].]]
The '''Triassic'''/Jurassic boundary occurs at 205.7 ± 4.0 Ma (million years ago).<ref name=Gradstein>{{ cite journal
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[[Image:Quebrada de Cafayate, Salta (Argentina).jpg|thumb|right|200px|The image shows rock strata in Cafayate, Argentina. Credit: travelwayoflife.]]
[[Image:BarstowFormationAnticlineMarch2010.jpg|thumb|right|200px|The image shows an anticline in the Barstow Formation (Miocene) at Calico Ghost Town near Barstow, California USA. Credit: [[commons:User:Wilson44691|Wilson44691]].]]
The image at the right shows rock strata in Cafayate, Argentina, the subject of [[stratigraphy]].


"'''Structural geology''' is the study of the three-dimensional distribution of rock units with respect to their deformational histories."<ref name=StructuralGeology>{{ cite web
|title=Structural geology, In: ''Wikipedia''
|publisher=Wikimedia Foundation, Inc
|location=San Francisco, California
|month=18 May
|year=2014
|url=https://en.wikipedia.org/wiki/Structural_geology
|accessdate=2014-05-18 }}</ref>
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==Technology==
{{main|Technology}}
[[Image:Methane measurements siberia.jpe.jpeg|thumb|right|200px|An under water, under ice bubble trap is installed on a lake in Siberia. Credit: Katey Walter.]]
Here at the right an under water, under-ice bubble trap is installed in a lake in Siberia.
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