September 2014

Amazing Gehlenite

Amazing Gehlenite

Locality: Caspar quarry, Bellerberg volcano, Ettringen, Mayen, Eifel, Rhineland-Palatinate, Germany FOV 3 mm. Collection Bernd Ternes, p...

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<span dir="ltr" style="font-family: Helvetica, Arial, 'lucida grande', tahoma, verdana, arial, sans-serif;">Fluorite - fluorescent<br />Rogerley Mine<br />Frosterley<br />Country Durham<span class="text_exposed_show" style="display: inline;"><br />United Kingdom<br /><br />Size: 9.5 x 7.3 x 4.5 cm<br /><br />Photo Copyright © SpiriferMinerals</span></span></div>
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Fluorite - fluorescent

Anticlines and Synclines

Structural Geology 7:40 PM

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This photo taken on U.S. 48 near Walnut Bottom, West Virginia, is an example of both anticlines and synclines in the same formation. Anticlines (the feature on the left half) are downward-curving (convex) folds in rock that resembles an arch. The central part, being the most exposed to erosion, display the oldest section of rock. Synclines (the feature in the center) are upward-curving (concave) folds in rock that resemble a trough. The central part contains the youngest section of rock.<span class="text_exposed_show" style="background-color: white; color: #141823; display: inline; font-family: "helvetica" , "arial" , "lucida grande" , "tahoma" , "verdana" , "arial" , sans-serif; font-size: 14px; line-height: 18px; text-align: right;"><br /></span>Thanks to Barbara am Ende for sharing this photo with the USGS Science in Action Flickr Group! </div>

Anticlines and Synclines

This photo taken on U.S. 48 near Walnut Bottom, West Virginia, is an example of both anticlines and synclines in the same formation. Ant...

Blue Haüyne With Sanidine Crystals

Minerals 8:22 PM

Blue Haüyne With Sanidine Crystals

What is Bowen's Reaction Series?

Igneous, Rocks 2:04 PM

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Bowen's reaction series is able to explain why certain types of minerals tend to be found together while others are almost never associated with one another. He experimented in the early 1900s with powdered rock material that was heated until it melted and then allowed to cool to a target temperature whereupon he observed the types of minerals that formed in the rocks produced.<br />
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The idealized progression which they determined is still accepted as the general model for the evolution of magmas during the cooling process. As with everything else in geology, there are exceptions to this rule , but for the most part it works.<br />
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<span style="font-family: inherit;">Bowen determined that specific minerals form at specific temperatures as a magma cools. At the higher temperatures associated with mafic and intermediate magmas, the general progression can be separated into two branches. </span><br />
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<span style="font-family: inherit;">The continuous branch describes the evolution of the plagioclase feldspars as they evolve from being calcium-rich to more sodium-rich. The discontinuous branch describes the formation of the mafic minerals olivine, pyroxene, amphibole, and biotite mica.</span><br />
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</span> <span style="font-family: inherit;">The weird thing that Bowen found concerned the discontinuous branch. At a certain temperature a magma might produce olivine, but if that same magma was allowed to cool further, the olivine would "react" with the residual magma, and change to the next mineral on the series (in this case pyroxene). </span><br />
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<span style="font-family: inherit;">Continue cooling and the pyroxene would convert to amphibole, and then to biotite. Mighty strange stuff, but if you consider that most silicate minerals are made from slightly different proportions of the same 8 elements, all we're really doing here is adjusting the internal crystalline lattice to achieve stability at different temperatures. Really no big deal.</span><br />
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</span> <span style="font-family: inherit;">At lower temperatures, the branches merge and we obtain the minerals common to the felsic rocks - orthoclase feldspar, muscovite mica, and quartz (the banana slug of the mineral world).</span><br />
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<span style="font-family: inherit;"> Simply put, the high temperature minerals, the first ones to crystallize in a mass of magma, are most unstable at the Earth's surface and quickest to weather because the surface is most different from the conditions under which they were created. On the other hand, the low temperature minerals are much more stable because the conditions at the surface are much more similar to the conditions under which they formed.<br /><br /> </span><br />
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What is Bowen's Reaction Series?

Bowen's reaction series is able to explain why certain types of minerals tend to be found together while others are almost never a...

Rhodochrosite, Hubnerite, Tetrahedrite, and Needle Quartz

Minerals 11:22 PM

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<span dir="ltr" style="font-family: Helvetica, Arial, 'lucida grande', tahoma, verdana, arial, sans-serif;">Rhodochrosite, Hubnerite, Tetrahedrite, and Needle Quartz<br /><br />Hedgehog Pocket, Main Stope Drift, Sweet Home Mine, Alma, Colorado<br /><br />Photo Copyright © exceptionalminerals<span class="text_exposed_show" style="display: inline;"><br /></span></span></div>
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Rhodochrosite, Hubnerite, Tetrahedrite, and Needle Quartz

Rhodochrosite, Hubnerite, Tetrahedrite, and Needle Quartz Hedgehog Pocket, Main Stope Drift, Sweet Home Mine, Alma, Colorado Photo Cop...

Download The General Dictionary of Geology

Books, Download 8:01 PM

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Edited by :<br />
Alva Kurniawan<br />
Department of Environmental Geography, Gadjah Mada University, Yogyakarta, Indonesia<br />
and :<br />
John Mc. Kenzie<br />
Department of Geology, University of Calgary, Calgary, Canada<br />
Jasmine Anita Putri<br />
Department of Geology, University of Melbourne, Melbourne, Australia<br />
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© Copyright 2009. Environmental Geographic Student Association (EGSA)<br />
Bulaksumur (postal code 55282), Yogyakarta, Indonesia<br />
Phone: (0274) 920340 Fax: (0274) 589595<br />
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<h4 style="text-align: left;">
Foreword</h4>
The subjects of this dictionary are most of geological terms but there are many terms that also related with geophysics, biology, astrophysics, and geography. Geology is an interesting subject in knowing history of Earth creation, creature evolution, ancient Earth life and Earth condition in the past; even find mine, coal, also oil deposit below Earth surface. Petrogeologist study geology to find mine, coal, or oil deposit. Geophysics scientist study geology for recognize the physical characteristics of Earth component such as magnetism, seismicity, elasticity, Earth thermodynamic, by physical experiments in a specific geological structure which consist of specific rocks and minerals. Biology scientist study geology for tracing the historical evolution of creature in its first appearance until this time. Geographers also study geology for recognize a spatial phenomenon of Earth surface that were formed or influenced with a sequences of geological event.<br />
<b><a href="https://drive.google.com/file/d/0B7T9nckRpMOkcGpka1ZUOXdaLTg/view?usp=sharing" target="_blank">Download link</a></b><br />
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<a href="https://docs.google.com/uc?authuser=0&id=0B7T9nckRpMOkcGpka1ZUOXdaLTg&export=download" target="_blank"><b>Download</b></a></div>

Download The General Dictionary of Geology

Edited by : Alva Kurniawan Department of Environmental Geography, Gadjah Mada University, Yogyakarta, Indonesia and : John Mc. Ken...

Why Does Earth Have Deserts?

climate, Desert, Environment, Geology 9:19 PM

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<tr><td class="tr-caption" style="text-align: center;">Hadley Cell scheme (Credit: ClimateTheory) </td></tr>
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Take a look at a physical map of the world. Thirty degrees on either side of the equator, you will see, distributed with suspicious regularity, a brown band of drylands circling the planet, a sere belt warding off greener climes: the deserts of the world.<br />
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They are positioned in the so-called Horse Latitudes, where constant high-pressure systems drive away the rain clouds, and swirl above the earth because of global temperature variations and the Coriolis Effect produced by the earth’s rotation in space.<br />
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These areas within the Horse Latitudes are under the influence of two bands of high atmospheric pressure called the subtropical high pressure belt or subtropical ridge which is formed by the sinking air of the Hadley cell.<br />
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The heating of the tropics produces a huge amount of rising warm, moist air that creates the Intertropical Convergence Zone, a band of thick cloud. This warm, moist air moves towards the poles at high altitudes and then cools and sinks in the mid-latitudes in both hemispheres, creating the Hadley Cell.<br />
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The Hadley Cell is possibly the most fundamental factor in the global climate system, redistributing the heat and moisture from the tropics to the higher latitudes. Many of the world's deserts are caused by these climatological phenomena. <br />
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Most deserts are hot. Within the latitudes of the Tropics of Cancer and Capricorn, the sun is directly overhead at noon on at least one day of the year. To the north or south of them, the sun never appears directly overhead, and is not as concentratedas the beam that reaches the tropical areas.<br />
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Deserts are not scattered randomly over the earth; the pattern of their occurrence is a result of the factors that produced them. The biggest world deserts appear in these two discontinuous belts ringing the globe. Because more land surface is in the Northern Hemisphere in the latitudes described, more deserts can be found in the Northern than the Southern Hemisphere.<br />
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Not all of our planets deserts are hot. Some of these drylands, like the Atacama of Chile, the Namib and Kalahari of southern Africa, and the western Australian desert, are shaped by cold oceanic currents that divert rain-laden air away from coastlines. Others, like the Great Basin of western United States, and the deserts of central and eastern Australia are the result of the “rainshadow effect”, through which coastal mountains take away the rain from the air before it passes inland.<br />
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There are deserts like the Gobi and Takla Makan deserts of Mongolia and China, which are simply so far away from the ocean that the winds lose any moisture they may hold long before reaching the far off continental interior, even what little water remains in the Indian-born clouds after they have scraped over the high Himalayas.<br />
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<u><i><span style="font-family: "trebuchet ms" , sans-serif;">The above post is reprinted from Materials provided by <a href="http://faculty.unlv.edu/landau/desertgeography.htm" rel="nofollow" target="_blank">University of Nevada</a>.</span></i></u></div>
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Why Does Earth Have Deserts?

Hadley Cell scheme (Credit: ClimateTheory) Take a look at a physical map of the world. Thirty degrees on either side of the equat...

Huge earth crack opened up in Sonora, Mexico

Tectonic 8:21 PM

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<span style="box-sizing: border-box;"><span style="font-family: inherit;">A one-kilometer long earth crack opened up on August 15, 2014, in Sonora, Mexico. The crack severed Highway 26 between the city of Hermosillo and the coast. At some points it is 5 meters wide and 8 meters deep.</span></span></div>
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<span style="box-sizing: border-box;"><span style="font-family: inherit;">According to El Imparcial newspaper, it is still unknown what caused the crack but Municipal Civil Protection believes that it was triggered by an underground water stream. Some speculate that an earthquake at the San Andreas Fault last Sunday may have been the cause.</span></span></div>
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Geological investigations are underway. Another crack was reported to have opened near Highway 4 in the same area.</div>
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Aerial drone footage. Credit: Hermosillo Desde El Cielo</div>
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Huge earth crack opened up in Sonora, Mexico

A one-kilometer long earth crack opened up on August 15, 2014, in Sonora, Mexico. The crack severed Highway 26 between the city of Herm...

Why Geologists Love Beer?

Geologist, Geology 2:16 PM

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<br /><span style="font-family: inherit;"><b><span style="font-family: Georgia,"Times New Roman",serif;">Fact: Geologists love beer.</span></b><br /></span><br />
There is abundant proof of this here at the American Geophysical Union meeting, the largest collection of earth scientists in the world.<br />
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The talks, workshops and poster sessions go from 8:00 a.m. to 6:00 p.m., but at 3:30 p.m. every day, for five days, kegs of beer are rolled out into the meeting. The beer flows nonstop for an hour and a half at around 10 different stations, and AGU organizers tell me they go through about 175 kegs during the week.<br />
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“Every other convention assumes that if you have a beer, your brain goes soft,” said Kathy Sullivan, who has been serving beer at the AGU meeting for 26 years. “But not the geophysicists. They think if you have a beer, you can still learn things. So they do.”<br />
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At the Thirsty Bear, the closest brewpub to the Moscone Convention Center where the annual meeting is held every December, the waitstaff claims this is the busiest week of the year for them. I heard from the Borehole Research Group at the Lamont Doherty Earth Observatory that one server at the Thirsty Bear said the staff can’t take vacation days during the AGU meeting “because the geologists are coming.”<br />
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So the real question is why the bond between geologists and beer is so strong. I decided to do some research this week to get to the bottom of the phenomenon. So, beer in hand, I asked a sampling of the 16,000 or so geologists, geophysicists, hydrologists and atmospheric scientists at the meeting and got some very interesting responses. (Full disclosure: I am also a geologist, and I love beer.)<br />
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The most popular theory was that it must have something to do with the amount of time spent outside doing fieldwork.<br />
“When it’s hot, and you’ve been hiking all day carrying 50 pounds of rocks, do you want a Merlot?” asked thermochronologist Jim Metcalf of Syracuse University. “No.”<br />
“It goes down a lot easier than water because a lot of the places we go, we can’t drink the water,” said structural geologist Jonathan Gourley of Trinity College.<br />
Geologists have been known to go to great lengths to chill their beer in the field, as well. A cold stream, a glacier or a patch of snow is handy, but many field areas are hot, dry and dusty. While doing field work in Mongolia, geologist Cari Johnson of the University of Utah and her colleagues cooled their beer with evaporation by wrapping the cans in toilet paper, pouring water on the paper and setting them out in the persistent wind to dry over and over until the beer was cold.<br />
Another theory is that beer makes for better science. I think this hypothesis has some merit, but requires further investigation (as long as I’m not in the control group).<br />
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“Science doesn’t work when people keep secrets and don’t share their data,” said Daniel Jaffe of the University of Washington. “And what could be better to help with the free flow of information?”<br />
Rick Saltus of the U.S. Geological Survey explained that because geologists often don’t have enough data to say definitively what went on millions of years ago, creativity is needed to fill in the gaps.<br />
“You have to think outside the box, you’ve got to release your inhibitions, and beer is one way to do that,” Saltus said. “Anything that helps you get to that epiphany, that realization of what’s there in the rocks and not easy to see but there to spin a story from.”<br />
A third theory offered up in various forms is that beer is simply part of the culture, something that has been handed down from advisor to student for generations.<br />
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“It’s accepted and encouraged to drink beer,” said geologist Cindy Martinez of the American Geological Institute. “Other scientists like beer, but it’s not necessarily socially acceptable to have your scientific meetings revolve around beer.”<br />
“I started getting on to wine and other stuff for a while, but I became an outcast among my geology friends,” said geologist Laura Webb of the University of Vermont. “So I had to retrain myself to drink brew.”<br />
Supporting the culture theory is the observation that earth science departments at academic institutions across the world almost invariably have a weekly get-together of some sort that revolves around beer.<br />
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At Stanford University, it’s called Friday Beer, and I hear that at UCLA it’s known as Liquidus. On Twitter, I confirmed that earth scientists at CalTech, The Borehole Research Group and the University of Sao Paulo in Brazil also have a weekly beer congregation.<br />
“I’ve been to a few geo departments around the world, and most of them have Friday Beer,” said Stanford biogeochemist Sharmini Pitter.<br />
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“We have three weekly beer gatherings,” said Christopher Harrison of the University of Miami.<br />
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None of the theories can be ruled out by this preliminary study, and neither can the possibility that all three are correct. Certainly, more research is needed. But one thing is clear: The love affair between geoscientists and beer is one for the eons.<br />
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<u><i><span style="font-family: "Trebuchet MS",sans-serif;"><span style="font-size: x-small;"><span style="background-color: white; color: #070809; line-height: 15.6000003814697px;">The above story is based on </span><a href="http://www.wired.com/2009/12/15943/" rel="nofollow" style="background-color: white; color: #004276; line-height: 15.6000003814697px; text-decoration: none;" target="_blank">materials</a>. <span style="background-color: white; color: #070809; line-height: 15.6000003814697px;">Note: Materials may be edited for content and length.</span><span style="background-color: white; color: #070809; line-height: 15.6000003814697px;"> .</span><a href="http://www.geologyin.com/" style="background-color: white; line-height: 15.6000003814697px;" target="_blank"> Geology In</a></span></span></i></u></div>
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Why Geologists Love Beer?

Fact: Geologists love beer. There is abundant proof of this here at the American Geophysical Union meeting, the largest collection of e...

How Does Bowen's Reaction Series Affect Chemical Weathering?

Igneous, Rocks, sedimentary 6:55 PM

How Does Bowen's Reaction Series Affect Chemical Weathering?

How Does Bowen's Reaction Series Affect Chemical Weathering? In general, minerals are most stable at the temperature and pressure a...

10 Pictures That Will Make You Want to Become a Geologist

Geologist, Geology 3:56 PM

10 Pictures That Will Make You Want to Become a Geologist

Mt. Head, Canada Geology is a magnificent and unique science. What makes it so unique, you may rightly ask; well, a good geologist...

How Plate Tectonics Works?

Earth History, Tectonic 11:15 AM

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<b>1.</b> There are two basic types of LITHOSPHERE: continental and oceanic. CONTINENTAL lithosphere has a low density because it is made of relatively light-weight minerals. OCEANIC lithosphere is denser than continental lithosphere because it is composed of heavier minerals. A plate may be made up entirely of oceanic or continental lithosphere, but most are partly oceanic and partly continental.<br />
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<b>2.</b>Beneath the lithospheric plates lies the ASTHENOSPHERE, a layer of the mantle composed of denser semi-solid rock. Because the plates are less dense than the asthenosphere beneath them, they are floating on top of the asthenosphere.<br />
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<b>3</b>.Deep within the asthenosphere the pressure and temperature are so high that the rock can soften and partly melt. The softened but dense rock can flow very slowly (think of Silly Putty) over geologic time. Where temperature instabilities exist near the core/mantle boundary, slowly moving convection currents may form within the semi-solid asthenosphere.<br />
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<b>4.</b>Once formed, convection currents bring hot material from deeper within the mantle up toward the surface.<br />
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<b>5.</b>As they rise and approach the surface, convection currents diverge at the base of the lithosphere. The diverging currents exert a weak tension or “pull” on the solid plate above it. Tension and high heat flow weakens the floating, solid plate, causing it to break apart. The two sides of the now-split plate then move away from each other, forming a DIVERGENT PLATE BOUNDARY.<br />
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<b>6.</b>The space between these diverging plates is filled with molten rocks (magma) from below. Contact with seawater cools the magma, which quickly solidifies, forming new oceanic lithosphere. This continuous process, operating over millions of years, builds a chain of submarine volcanoes and rift valleys called a MID-OCEAN RIDGE or an OCEANIC SPREADING RIDGE.<br />
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<b>7.</b>As new molten rock continues to be extruded at the mid-ocean ridge and added to the oceanic plate (6), the older (earlier formed) part of the plate moves away from the ridge where it was originally created.<br />
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<b>8.</b>As the oceanic plate moves farther and farther away from the active, hot spreading ridge, it gradually cools down. The colder the plate gets, the denser (“heavier”) it becomes. Eventually, the edge of the plate that is farthest from the spreading ridges cools so much that it becomes denser than the asthenosphere beneath it.<br />
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<b>9.</b>As you know, denser materials sink, and that’s exactly what happens to the oceanic plate—it starts to sink into the asthenosphere! Where one plate sinks beneath another a subduction zone forms.<br />
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<b>10.</b>The sinking lead edge of the oceanic plate actually “pulls” the rest of the plate behind it—evidence suggests this is the main driving force of subduction. Geologists are not sure how deep the oceanic plate sinks before it begins to melt and lose its identity as a rigid slab, but we do know that it remains solid far beyond depths of 100 km beneath the Earth’s surface.<br />
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<b>11.</b>Subduction zones are one type of CONVERGENT PLATE BOUNDARY, the type of plate boundary that forms where two plates are moving toward one another. Notice that although the cool oceanic plate is sinking, the cool but less dense continental plate floats like a cork on top of the denser asthenosphere.<br />
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<b>12.</b>When the subducting oceanic plate sinks deep below the Earth’s surface, the great temperature and pressure at depth cause the fluids to “sweat” from the sinking plate. The fluids sweated out percolate upward, helping to locally melt the overlying solid mantle above the subducting plate to form pockets of liquid rock (magma).<br />
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<b>13.</b>The newly generated molten mantle (magma) is less dense than the surrounding rock, so it rises toward the surface. Most of the magma cools and solidifies as large bodies of plutonic (intrusive) rocks far below the Earth’s surface. These large bodies, when later exposed by erosion, commonly form cores of many great mountain ranges that are created along the subduction zones where the plates converge.<br />
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<b>14.</b>Some of the molten rock may reach the Earth’s surface to erupt as the pent-up gas pressure in the magma is suddenly released, forming volcanic (extrusive) rocks. Over time, lava and ash erupted each time magma reaches the surface will accumulate—layer upon layer—to construct volcanic mountain ranges and plateaus, such as the Cascade Range and the Columbia River Plateau (Pacific Northwest, U.S.A.).</div>
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How Plate Tectonics Works?

1. There are two basic types of LITHOSPHERE: continental and oceanic. CONTINENTAL lithosphere has a low density because it is made of...

How to Study and Identify the Minerals Samples?

Geology, Mineralogy 8:17 PM

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<span style="font-family: inherit;">     </span><br />
<span style="font-family: inherit;">In simple terms, our planet is just a big ball of very hot stuff which, at the surface where it is exposed to space, has cooled to form crystalline solids (igneous rocks) composed of minerals. Minerals in turn are combinations of elements, which are made of smaller particles, which are made of smaller particles, which are made of..... who knows what.</span><br />
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<span style="font-family: inherit;">To be classified as a mineral, a substance must be an inorganic, naturally formed solid, with a specific chemical formula and a fixed internal structure. For example, coal is not a mineral (it's organic), but snow meets all five (5) requirements and therefore is a mineral.</span><br />
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<span style="font-family: "georgia" , "times new roman" , serif;"><b><span style="font-family: inherit;">Study the Physical </span>properties of it:</b></span></h3>
<b style="font-family: 'Comic Sans MS';">Luster:</b><span style="font-family: "comic sans ms";"> </span><span style="font-family: inherit;">The quantity and quality of light reflected from the surface. Most identification schemes begin with a simple classification based on luster. Because of this, luster is the first fundamental test to be made when identifying any mineral. </span><br />
<span style="font-family: inherit;"> </span><span style="font-family: "comic sans ms";">Metallic</span><span style="font-family: "comic sans ms";">:</span><span style="font-family: inherit;"> looks like a metal. Metallic minerals are commonly shiny and opaque</span><br />
<span style="font-family: "comic sans ms";">Non-metallic: </span><span style="font-family: inherit;">doesn't look like a metal.</span><br />
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<b style="font-family: 'Comic Sans MS';">Color:</b><span style="font-family: "comic sans ms";"> </span><span style="font-family: inherit;">Obvious, but not always definitive. Sulfur is (almost) always yellow, and there are a few others, but not many minerals have a fixed color. Small amounts of impurities can drastically change a mineral's color.</span><br />
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<b style="font-family: 'Comic Sans MS';">Streak:</b><span style="font-family: "comic sans ms";"> </span><span style="font-family: inherit;">The color of the powdered mineral. The test is usually performed by scraping the mineral across a piece of unglazed porcelain. Streak can be definitive. Good examples include hematite (always red-brown no matter what form it's in) and chromite (distinguished from the hundreds of other black minerals by its chocolate-brown streak).</span><br />
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<b style="font-family: 'Comic Sans MS';">Hardness:</b><span style="font-family: "comic sans ms";"> </span><span style="font-family: inherit;">Hardness is the resistance of a mineral to scratching. It does NOT refer to how easily the mineral is broken. Hardness is a measure of the bonding strength between atoms. If these bonds are strong, the mineral is not easily scratched. Minerals with weaker bonds are more easily scratched. </span><br />
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<span style="font-family: "comic sans ms";"><b>Fracture:</b> </span><span style="font-family: inherit;">The mineral just breaks, leaving an uneven surface. Most are irregular but there are some special cases (ex: the conchoidal fractures common to quartz and glass)</span><br />
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<span style="font-family: "comic sans ms";"><b>Cleavage:</b> </span><span style="font-family: inherit;">The mineral splits along closely spaces parallel planes, leaving a mirror surface which will flash at you if rotated in the light.<span style="background-color: white; line-height: 16px;">Controlled by crystalline structure and chemical bonding.</span><span style="background-color: white; line-height: 16px;"> </span></span><br />
<span style="font-family: inherit;"><span style="background-color: white; line-height: 16px;">0, 1, 2, 3, 4, and 6 cleavage planes can exist. </span><span style="background-color: white; line-height: 16px;">Most difficult physical property for students to understand and identify.</span></span><br />
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<b style="font-family: 'Comic Sans MS';">Specific Gravity:</b><span style="font-family: inherit;"> Defined as "the weight of a specific volume of a mineral divided by the weight of an equal volume of water (at 4°C.)" Since water is always 1.0, it's the same number as density without any units (they cancel). This is almost impossible to measure in the field, but a rough approximation and be determined.</span></div>
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<b style="font-family: 'Comic Sans MS';">Magnetism:</b><span style="font-family: "comic sans ms";"> </span><span style="font-family: inherit;">Magnetite is naturally magnetic.</span><span style="font-family: "comic sans ms";"> </span></div>
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<b style="font-family: 'Comic Sans MS';">Taste:</b><span style="font-family: "comic sans ms";"> </span><span style="font-family: inherit;">Some minerals have a distinctive taste. Notable examples include Halite (rock salt), and Chalcanthite (a copper sulfate - be careful with this one!!). I don't generally recommend the taste test.</span></div>
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<b style="font-family: 'Comic Sans MS';">Smell:</b><span style="font-family: "comic sans ms";"> </span><span style="font-family: inherit;">Some minerals have a distinctive odor. Sulfur is a good example.</span></div>
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<b>s<a href="http://www.geologyin.com/" target="_blank">ee also: </a></b></div>
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<a href="http://www.geologyin.com/2014/12/10-most-rare-gemstones-in-world-rarer.html" target="_blank"><span style="color: black;">10 Most Rare Gemstones in the World Rarer than a Diamond</span></a></div>
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<a href="http://www.geologyin.com/2015/02/types-of-folds-with-photos.html" target="_blank">Types of folds with Photos</a></div>
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<span class="" data-offset-key="cimor-0-0" data-reactid=".9t.1:4.0.$right.0.0.0.0.1.0.0.1.0.$cimor.0:$cimor-0-0"><a href="http://www.geologyin.com/2014/11/how-to-identify-minerals-in-10-steps.html" target="_blank">How to Identify Minerals in 10 Steps (photos)</a></span></div>
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</div>

How to Study and Identify the Minerals Samples?

In simple terms, our planet is just a big ball of very hot stuff which, at the surface where it is exposed to space, has cooled to f...

What Is the Difference Between Quartz and White Feldspar in Rocks?

Igneous, Mineralogy, Rocks 2:21 PM

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<tr><td class="tr-caption" style="text-align: center;"><b><span style="font-family: "georgia" , "times new roman" , serif;">Feldspar Red Circles, </span></b><b><span style="font-family: "georgia" , "times new roman" , serif;"><span style="font-family: Georgia, "Times New Roman", serif;"><b><span style="font-family: "georgia" , "times new roman" , serif;">Quartz yellow circles. </span></b></span></span></b></td></tr>
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<h3 style="text-align: left;">
<span style="font-size: small;"><span style="font-family: Georgia, "Times New Roman", serif;">So,
 if the mineral has cleavage and sparkles, it may be feldspar. If no 
sparkles, no matter how you rotate it in the light, it may be quartz.</span></span></h3>
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<b><span style="font-family: "georgia" , "times new roman" , serif;"><br /></span></b>
<b><span style="font-family: "georgia" , "times new roman" , serif;">Feldspar </span></b>grows (when allowed to) into rectangular crystals, and then usually breaks the same way. This breakage pattern is called cleavage, and feldspar has two directions of cleavage that meet at close to a 90 degree angle (just like a stairway). If you see little sparkles when you look at the rock, the flashes may be the light reflecting off the mirror-like cleavage surfaces.<br />
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<span style="font-family: Georgia, "Times New Roman", serif;"><b><span style="font-family: "georgia" , "times new roman" , serif;">Quartz </span></b></span>has no cleavage (it breaks with a conchoidal fracture - just like obsidian, or the curved fractures that you can often see in the windshield of your car after a rock hits it), so usually no mirror-like flashes of light. The bad news is that sometimes the curved conchoidal surfaces can flash as well, but this usually happens with the clear varieties of quartz (which you already know isn't feldspar anyway).<br />
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<br />
<span style="font-family: Georgia, "Times New Roman", serif;"><a href="http://www.geologyin.com/2014/12/how-to-classify-igneous-rocks-into.html" target="_blank">How to Classify Igneous Rocks Into (Ultramafic, Mafic, Intermediate and Felsic)? </a></span></div>

What Is the Difference Between Quartz and White Feldspar in Rocks?

Feldspar Red Circles, Quartz yellow circles. So, if the mineral has cleavage and sparkles, it may be feldspar. If no sparkles, no ...

Iridescent Pyrite

Minerals 11:44 AM

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<span dir="ltr" style="font-family: Helvetica, Arial, 'lucida grande', tahoma, verdana, arial, sans-serif;">Iridescent Pyrite<br /><br />Location: Shangbao Mine, Leiyang Co., Hengyang Pref., Hunan Province, China<br />Size: 1.9" x 1.8" x 1.5"<br /><span class="text_exposed_show" style="display: inline;"><br />Photo Copyright © Treasure Mountain Mining</span></span></div>
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Iridescent Pyrite

Iridescent Pyrite Location: Shangbao Mine, Leiyang Co., Hengyang Pref., Hunan Province, China Size: 1.9" x 1.8...

Gorgeous Agate, Morocco.

Minerals 11:52 AM

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Kerrouchene<br />
Khenifra Province<br />
Morocco<br />
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Size: 8x6.4x4.6 cm<br />
Weight: 270 g<br />
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Description:<br />
Aesthetic, colorful agate from Morocco, polished on one side.<br />
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credit : spiriferminerals .com</div>

Gorgeous Agate, Morocco.

Kerrouchene Khenifra Province Morocco Size: 8x6.4x4.6 cm Weight: 270 g Description: Aesthetic, colorful agate from Morocco, p...

Indicolite Tourmaline With a Large Pink Lepidolite

Minerals 11:19 PM

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<span style="font-family: inherit;"><span aria-live="polite" class="fbPhotosPhotoCaption" data-ft="{"tn":"K"}" id="fbPhotoSnowliftCaption" style="background-color: white; color: #141823; display: inline; font-size: 14px; line-height: 18px; outline: none; text-align: right; width: auto;" tabindex="0"><span class="hasCaption"><br /><span dir="ltr">Gorgeous specimen of blue Indicolite Tourmaline with a large pink Lepidolite crystal to its right and a smaller Quartz crystal to its left. Specimens like this are what makes this such a great hobby. Incredible color and display!<br /><br />From the Paprok Mine, Kamdesh District, Nuristan Province, Afghanistan.</span></span></span><span class="fbPhotoTagList" id="fbPhotoSnowliftTagList" style="background-color: white; color: #141823; display: inline; font-size: 14px; line-height: 18px; text-align: right;"><span class="fcg" style="color: #9197a3;"> </span></span></span></div>

Indicolite Tourmaline With a Large Pink Lepidolite

Gorgeous specimen of blue Indicolite Tourmaline with a large pink Lepidolite crystal to its right and a smaller Quartz crystal to its lef...

What Is the Difference Between Phaneritic and Aphanitic Rocks?

Igneous, Rocks 9:17 PM

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<tr><td style="text-align: center;"><a href="http://3.bp.blogspot.com/-MrrzZci6p_I/VA3vpffRn5I/AAAAAAAABns/jMPmL5OJY1U/s1600/granitic_minerals.jpeg" imageanchor="1" style="margin-left: auto; margin-right: auto;"><img alt="Coarse Grained Texture (Phaneritic), Mineral Grains Easily Visible (Grains Several Mm in Size or Larger)" border="0" height="480" src="https://3.bp.blogspot.com/-MrrzZci6p_I/VA3vpffRn5I/AAAAAAAABns/jMPmL5OJY1U/s640/granitic_minerals.jpeg" title="" width="640" /></a></td></tr>
<tr><td class="tr-caption" style="text-align: center;">A hand specimen of granite with phaneritic (coarse grained) texture.  Principal minerals are Potassium Feldspar, Biotite Mica, and Quartz.</td></tr>
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<b><span style="font-family: "georgia" , "times new roman" , serif;">Coarse Grained Texture (Phaneritic), Mineral Grains Easily Visible (Grains Several Mm in Size or Larger)</span></b></h4>
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<span style="font-family: inherit;"><b>Phaneritic </b>textured rocks are comprised of large crystals that are clearly visible to the eye with or without a hand lens or binocular microscope. The entire rock is made up of large crystals, which are generally 1/2 mm to several centimeters in size; no fine matrix material is present. This texture forms by slow cooling of magma deep underground in the plutonic environment. </span><br />
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<script async="" src="//pagead2.googlesyndication.com/pagead/js/adsbygoogle.js"></script>The first-formed crystals tend to have regular shapes because they grow freely into the surrounding liquid. Later-formed crystals find themselves competing for space with their solid neighbors; they are forced to fill in the irregular gaps. Thus, you can often figure out the relative order in which the minerals crystallized from the magma.<br />
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<tr><td style="text-align: center;"><a href="http://3.bp.blogspot.com/-KT1oOtfcCtc/VA3xPOKeK8I/AAAAAAAABn4/9m81SIl_ZmI/s1600/basalt_handspec_aphanetic.jpeg" imageanchor="1" style="margin-left: auto; margin-right: auto;"><img alt="Fine Grained Texture (Aphanitic), Mineral Grains Smaller Than 1mm (Need Hand Lens or Microscope to See Minerals)" border="0" height="480" src="https://3.bp.blogspot.com/-KT1oOtfcCtc/VA3xPOKeK8I/AAAAAAAABn4/9m81SIl_ZmI/s640/basalt_handspec_aphanetic.jpeg" title="" width="640" /></a></td></tr>
<tr><td class="tr-caption" style="text-align: center;">A hand specimen of basalt with aphanitic (fine grained) texture.  The dark color is due to abundant dark colored minerals (pyroxene, hornblende).</td></tr>
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<b><span style="font-family: "georgia" , "times new roman" , serif;">Fine Grained Texture (Aphanitic), Mineral Grains Smaller Than 1mm (Need Hand Lens or Microscope to See Minerals)</span></b></h4>
<b>Aphanitic </b>texture consists of small crystals that cannot be seen by the eye with or hand lens. The entire rock is made up of small crystals, which are generally less than 1/2 mm in size. This texture results from rapid cooling in volcanic or hypabyssal (shallow subsurface) environments. These extremely fine-grained, crystalline fabrics are formed when a magma solidifies in response to a very rapid loss of heat and dissolved gases. Emplacement in high-level dykes or eruption on to the surface can result in the development of aphanitic fabrics.<span style="font-family: "palatino" , "garamond";"><br />
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Crystalline rocks with mineral grains that cannot be distinguished from one another without magnification have an aphanitic igneous texture. Igneous rocks form by crystallization of minerals from liquid magma rising into the upper portion of Earth's crust from the lower crust and underlying mantle. Igneous rock texture indicates the rate of magmatic cooling.<br />
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Crystallization takes place either slowly in deeply buried intrusions called plutons, or rapidly at the earth's surface where magma has been extruded as lava by volcanic activity. Igneous rocks are therefore classified as either intrusive (plutonic) or extrusive (volcanic). Slow, undisturbed cooling in a well-insulated pluton is conducive to orderly arrangement of atoms and molecules into large, well-formed crystals .<br />
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Rapid cooling from a lava flow is not. Intrusive igneous rocks thus have coarse-grained, or phaneritic, textures with visible crystals, and extrusive igneous rocks have fine-grained, or aphanitic, texture. Volcanic glass , called obsidian , forms when lava is quenched and solidified so quickly that the silicate ions in the melt form no orderly atomic structure.<br />
<h3 style="text-align: left;">
<span style="color: white;"><b><span style="font-family: "georgia" , "times new roman" , serif;">Coarse Grained Texture (Phaneritic), Mineral Grains Easily Visible (Grains Several Mm in Size or Larger)</span></b></span></h3>
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<a href="http://www.geologyin.com/2014/09/how-can-i-tell-difference-between.html" target="_blank">What Is the Difference Between Quartz and White Feldspar in Rocks?</a><span style="font-family: "palatino" , "garamond";"><br />
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What Is the Difference Between Phaneritic and Aphanitic Rocks?

A hand specimen of granite with phaneritic (coarse grained) texture. Principal minerals are Potassium Feldspar, Biotite Mica, and Quartz...

Amazing Blue Sapphire

Minerals 8:18 PM

Amazing Blue Sapphire

Today's Luxury eye Candy is just awesome, it's this Blue Sapphire weighing 72.9 cts from Graves Hill, Australia! Sapphire is...

Green Epidote Clusters Quartze

Minerals 6:08 PM

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Great, aesthetic specimen of green epidote clusters on white, sharp 
quartzes. Great contrast and form. Specimen mounted on acrylic base.<br />
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From: Imilchil, Er Rachidia Province, Morocco<br />
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Credit: Spirifer Minerals<br />
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Green Epidote Clusters Quartze

Great, aesthetic specimen of green epidote clusters on white, sharp quartzes. Great contrast and form. Specimen mounted on acrylic ba...

How Can a Volcano Erupt Mafic Lava One Time, and Then Felsic Lava Another Time?

edu, volcano 7:58 AM

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<a href="http://3.bp.blogspot.com/-sap8D9AG9QU/VA03MgB5HiI/AAAAAAAABnc/SkaSXollq84/s1600/kilauea-vent-lg.jpg" imageanchor="1" style="margin-left: 1em; margin-right: 1em;"><img alt="How Can a Volcano Erupt Mafic Lava One Time, and Then Felsic Lava Another Time?" border="0" height="400" src="https://3.bp.blogspot.com/-sap8D9AG9QU/VA03MgB5HiI/AAAAAAAABnc/SkaSXollq84/s1600/kilauea-vent-lg.jpg" title="" width="640" /></a></div>
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<br />There are several ways, but one of the common ones happens when the magma in a magma chamber has time to separate (called "differentiation" ). Just like lighter grease will bubble to the top of a pan of spaghetti sauce, so will felsic magma bubble upwards in a magma chamber.<br />
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So what you can get is a violent felsic explosion, followed by an intermediate or mafic eruption after the pressure is released and magma from deeper in the magma chamber can be released. For example: Crater Lake in Oregon. The initial eruption blew off the top of Mt. Mazama and made the hole for Crater Lake, but then a mafic cinder cone erupted inside the caldera and formed Wizard Island.</div>

How Can a Volcano Erupt Mafic Lava One Time, and Then Felsic Lava Another Time?

There are several ways, but one of the common ones happens when the magma in a magma chamber has time to separate (called "differen...

Incredible Spray of Azurite Crystals

Minerals 11:11 PM

Incredible Spray of Azurite Crystals

Credit: The Mineral Gallery, Inc Incredible specimen featuring a dramatic spray of Azurite crystals with ps to Malachite! For a ...

What Causes the Plates Tectonic to Move?

edu, in, Tectonic 7:39 PM

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<a href="http://1.bp.blogspot.com/-SClOwMMEM00/VAs2u7SYruI/AAAAAAAABnM/GyjN5Mh0DDE/s1600/plate2-s9t7h6.png" imageanchor="1" style="margin-left: 1em; margin-right: 1em;"><img alt="What Causes the Plates Tectonic to Move?" border="0" height="306" src="https://1.bp.blogspot.com/-SClOwMMEM00/VAs2u7SYruI/AAAAAAAABnM/GyjN5Mh0DDE/s1600/plate2-s9t7h6.png" title="" width="400" /></a></div>
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Let's play with some numbers. Assume that average continental crust weighs in at about 10 cubic feet to the ton. If a ton equals 2000 pounds, this means that each cubic foot of continental crust weighs about 200 pounds. How big is North America?<br />
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Since we're just trying to get an "order of magnitude" number here, lets assume that on average it's approximately 2500 miles from east to west, 5000 miles from north to south, and 35 miles thick. Let's see... converting to feet that makes 1.3 X 10<sup>7</sup> feet times 2.6 X 10<sup>7</sup> feet times 35 feet which equals 1.2 X 10<sup>16</sup> cubic feet, times 200 pounds equals 2.4 X 10<sup>18</sup> pounds. In normal numbers this is the same as 2,400,000,000,000,000,000 pounds (2.4 quintillion). Okay, nudge it 2 centimeters to the west, please!<br />
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With this much mass we can start to rule out some possibilities. The gravitational attraction of the moon just doesn't do the job. Nor does the attraction of the sun. Centrifugal force from the rotation of the earth probably can't get it done, and I really doubt that it's 3 big guys with a rope.<br />
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Probably the most logical place to look is inside the earth. We already know that it's pretty hot down there, and we also know that heat and density are related. The short version is that when something is heated up, there is a corresponding decrease in density, and the material rises. This is the reason hot air balloons work, and why the cold water is near the bottom of the lake and not on top.<br />
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This process also drives the major wind patterns. Rock is no different, and when heated it lowers in density and wants to go up. So far so good. The problem is that if it rises it's going to leave a void where it was, and we sure can't have that. Just like in the lake (or the atmosphere), water, air, or in this case rock, moves in from the side to fill the hole. But that just leaves another hole, so something has to move in to fill that one, and so on and so on until the stuff which moved in the first place does the filling and the circle is complete.<br />
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We call this circular pattern of density driven material a "convection cell," and as I said it's this convection which powers the major global wind patterns, affects the ocean currents... and may well drive the plates. Deep beneath the crust the rock is VERY hot, and while there is probably too much pressure for it to be a liquid, it's still somewhat mobile, and individual atoms and such can kinda/sorta ooze about, setting up convection cells which may carry the plates along where they rub up against the surface crust.<br />
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Most geologists accept convection currents as the most likely mechanism for plate motions. One of the biggest questions now relates to how deep within the mantle the convection cells extend. Pictured below is a diagram of "Deep Mantle Convection." Many geologists favor this concept. Many others favor shallow mantle convection. Others postulate multiple layers of convection. And I know 3 big boys in Grants Pass who are still looking for a rope.<br />
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What Causes the Plates Tectonic to Move?

Let's play with some numbers. Assume that average continental crust weighs in at about 10 cubic feet to the ton. If a ton equals ...

How Does Bowen's Reaction Series Relate to the Classification of Igneous Rock?

Igneous, Rocks 7:51 PM

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<a href="http://4.bp.blogspot.com/-s1_HG3CklWQ/VAiX01gx_7I/AAAAAAAABls/-R_1tSl4R9Q/s1600/BowensReactionSeries.jpg" style="margin-left: 1em; margin-right: 1em;"><img alt="How Does Bowen's Reaction Series Relate to the Classification of Igneous Rock?" border="0" height="384" src="https://4.bp.blogspot.com/-s1_HG3CklWQ/VAiX01gx_7I/AAAAAAAABls/-R_1tSl4R9Q/w640-h384/BowensReactionSeries.jpg" title="How Does Bowen's Reaction Series Relate to the Classification of Igneous Rock?" width="640" /></a></div>
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The Bowen reaction series is a description of how magma's minerals change as they cool. It’s a means of ranking common igneous silicate minerals by the temperature at which they crystallise.<a href="http://www.geologyin.com/2014/09/what-is-bowens-reaction-series.html" target="_blank"> Bowen's Reaction Series</a> describes the temperatures at which different common silicate minerals change from the liquid to solid phase (or from the solid to liquid).<br />
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<span style="font-family: "georgia" , "times new roman" , serif;">The Principles that Bowen realized are as follows:</span></h3>
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<li>A) As a melt cools minerals crystallize that are in thermodynamic equilibrium with the melt (dissolution equals crystallization; if no equilibrium either crystallization will dominate [supersaturation], or dissolution [undersaturated]).</li>
<li>B) As the melt keeps cooling and minerals keep crystallizing, the melt will change its composition.</li>
<li>C) The earlier formed crystals will not be in equilibrium with this melt any more and will be dissolved again to form new minerals. In other words: these crystals react with the melt to form new crystals, therefore the name reaction series.</li>
<li>D) The common minerals of igneous rocks can be arranged into two series, a continuous reaction series of the feldspars, and a discontinuous reaction series of the ferromagnesian minerals (olivine, pyroxene, hornblende, biotite)</li>
<li>E) This reaction series implies that from a single "parental magma" all the various kinds of igneous rocks can be derived by Magmatic Differentiation.</li>
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In general terms, the higher temperature minerals have a higher proportion of iron and magnesium, and are therefore considered to be mafic. The lower temperature minerals are related to the opposite end of the compositional spectrum (lower in iron and magnesium, higher in silicon and oxygen), and are considered to be felsic. Some minerals are clearly mafic, some are clearly felsic, and some fall in between these two extremes.<br />
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Common mafic minerals include olivine, pyroxene, amphibole, biotite mica, and the plagioclase feldspars. Common felsic minerals include quartz, muscovite mica, and the orthoclase feldspars. Different magma compositions obviously result in different igneous rocks.<br />
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The other factor which contributes to the differences in igneous rocks relates to the length of time it took for the magma to crystallize. In general terms, the faster the rate of cooling (common to extrusive, volcanic rocks), the smaller the resulting mineral grains. Slower cooling histories (commonly intrusive) result in a coarser-grained rock.<br />
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Mafic igneous rocks (olivine, pyroxene, and the plagioclase feldspars) include basalt (extrusive) and gabbro (intrusive), while felsic igneous rocks (quartz, amphibole, mica, and the orthoclase feldspars) include granite (intrusive) and rhyolite (extrusive). <br />
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Magmas of intermediate composition result in the crystallization of intermediate minerals (actually a mix of the mid-range minerals: amphibole and both types of feldspar), with the common igneous rocks being andesite (extrusive) and diorite (intrusive).<br />
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Simply put, the high temperature minerals, the first ones to crystallize in a mass of magma, are most unstable at the Earth's surface and quickest to weather because the surface is most different from the conditions under which they were created. On the other hand, the low temperature minerals are much more stable because the conditions at the surface are much more similar to the conditions under which they formed.<br />
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See also: <br />
<a href="http://www.geologyin.com/2014/12/how-to-classify-igneous-rocks-into.html" target="_blank">How to Classify Igneous Rocks Into (Ultramafic, Mafic, Intermediate and Felsic)?</a><br />
<a href="http://www.geologyin.com/2015/08/using-qapf-diagram-to-classify-igneous.html" target="_blank">How to Use QAPF Diagram to Classify Igneous Rocks? </a></div>

How Does Bowen's Reaction Series Relate to the Classification of Igneous Rock?

The Bowen reaction series is a description of how magma's minerals change as they cool. It’s a means of ranking common igneous sili...

What Are the Most Important Types of Rock in the Crust?

Igneous, Rocks 1:03 AM

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<a href="http://1.bp.blogspot.com/-xOwySuZtUIo/VAePTjz4ULI/AAAAAAAABlc/28NCwE3GZek/s1600/Granite-Basalt_contact.jpg" style="margin-left: 1em; margin-right: 1em;"><img alt="What Are the Most Important Types of Rock in the Crust?" border="0" height="474" src="https://1.bp.blogspot.com/-xOwySuZtUIo/VAePTjz4ULI/AAAAAAAABlc/28NCwE3GZek/w640-h474/Granite-Basalt_contact.jpg" title="What Are the Most Important Types of Rock in the Crust?" width="640" /></a></div>
<br />Basalt and granite actually have quite a bit in common. Both are igneous rocks, which means that they cooled from a magma (the earth gets very hot just below the surface, and there is lots of liquid rock available). Both are made up of minerals from the silicate group, so both have large amounts of silicon and oxygen. Both will hurt if you drop a big piece on your toe. But there are several important differences, too. These differences help define and explain how the earth works.<br />
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<b>Granite</b> is great stuff! Not only is it my personal favorite, it is without a doubt the most common rock type on the continental land masses. Yosemite Valley in the Sierra Nevada and Mt. Rushmore are two notable examples of granitic rocks. But granitic "basement rock" can be found just about everywhere east of the Rockies if you're willing to dig through the dirt and sedimentary rocks at the surface. Granite is intrusive, which means that the magma was trapped deep in the crust, and probably took a very long time to cool down enough to crystallize into solid rock. This allows the minerals which form plenty of time to grow, and results in a coarse-textured rock in which individual mineral grains are easily visible.<br />
<br />Granite is the ultimate silicate rock. As discussed elsewhere in greater detail, on average oxygen and silicon account for 75% of the earth's crust. The remaining 25% is split among several other elements, with aluminum and potassium contributing the most to the formation of the continental granitic rocks. Relatively small amounts of iron and magnesium occur, but since they have generally higher densities it's not surprising that there isn't very much in the granite. Due to the process of differentiation, most of the heavier elements are moving towards the core of the earth, allowing the silicon and oxygen to accumulate on the surface. And accumulate it has. Enough granitic "scum" has differentiated to the surface to cover 25% to 30% of the earth with the good stuff. We call this purified material felsic because of the relatively high percentage of silica and oxygen.<br />
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<b>Basalt</b> is extrusive. The magma from which it cools breaks through the crust of the earth and erupts on the surface. We call these types of events volcanic eruptions, and there are several main types. Thevolcanoes that make basalt are very common, and tend to form long and persistent zones of rifting in nearly all of the ocean basins. We now believe that these undersea volcanic areas represent huge spreading ridges where the earth's crust is separating. It's a lot like a cut on your arm, which will bleed until a scab forms. Basaltic magma is like the blood of the earth - it's what comes out when the earth's skin is cut the whole way through. As an eruption ends, the basalt "scab" heals the wound in the crust, and the earth adds some new seafloor crust. Because the magma comes out of the earth (and often into water) it cools very quickly, and the minerals have very little opportunity to grow. Basalt is commonly very fine grained, and it is nearly impossible to see individual minerals without magnification.<br />
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Basalt is considered a mafic silicate rock. Among other characteristics, mafic minerals and rocks are generally dark in color and high in specific gravity. This is in large part due to the amount of iron, magnesium, and several other relatively heavy elements which "contaminate" the silica and oxygen. But this heavy stuff really isn't happy near the surface, and will take any opportunity it can to head for deeper levels. The trick is to heat the basalt back up again so it can melt and give the iron another shot at the core. It wants to be there, and heat is the key which unlocks the door.<br />
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<b>As it turns out</b>, most of the ocean floor is basalt, and most of the continents are granite. Basaltic crust is dark and thin and heavy, while granite is light and accumulates into continent-sized rafts which bob about like corks in this "sea of basalt." When a continent runs into a piece of seafloor, it's much like a Mac truck running into a Volkswagon. Not very pretty, but at least there's a clear winner. And the seafloor basalt ends up in pretty much the same position as does the VW - under the truck (or continent, as the case may be). This may seem like a drag for the basalt, but remember that it isn't all that happy on the surface anyway, and this gives it the heat it needs to re-melt and try to complete the differentiation process which was so rudely interrupted at the spreading ridge. If successful and allowed to continue, what's left behind is a "purified" magma with most of the iron, magnesium, and other heavy elements removed. When it cools, guess what forms? And the continental land mass just got a wee bit larger.</div>

What Are the Most Important Types of Rock in the Crust?

Basalt and granite actually have quite a bit in common. Both are igneous rocks, which means that they cooled from a magma (the earth gets...

Topaz Crystal From Mexico

Minerals 11:25 PM

Topaz Crystal From Mexico

Geology In