Thursday, December 6, 2007
Wednesday, December 5, 2007
Diamonds
As christmas is quickly approching, I was thinking of all the gifts that I'd love to give, but, alas, cannot afford. So instead I thought I'd talk about something that I like. Diamonds.
Ever wonder where a diamond comes from? This is an amazing story of suspense and intrigue. Well maybe...
Ok, the diamond on your hand or on the hand of the person next to you was formed at a very violent place. And no, I don't mean all fo the conflict taking place in Africa over the mining of the diamond. diamonds are formed at a a depth of about 100km (60 miles) down in the mantle of the earth. The diamond itself is a crystallized carbon, which in fact is the hardest known substance on earth. What this means is that a diamond can scratch anything. But then in a moment of great violence, magama and diamonds are thrust up toward the surface through a conduit called a kimberlite pipe. The name kimberlite comes from a town in Africa, Kimberly. Many of these pipes exist in South Africa, but recently, many have been discovered in Brazil and even Canada! The pipes themselves are not very interesting, but as you can see from the diagram, the diamonds are located throughout the pipe- and that is of course what we are all interested in.
The pipe is then mined, and the raw diamonds are found. The diamonds are so valueable that the mining companies often justify the processing of large amounts of rock just to get a few diamonds.
These raw diamonds are then cut to form the many cuts that we enjoy today. I personally like the brilliant cut, below is a guide of how to facet the diamonds:
Ever wonder where a diamond comes from? This is an amazing story of suspense and intrigue. Well maybe...
Ok, the diamond on your hand or on the hand of the person next to you was formed at a very violent place. And no, I don't mean all fo the conflict taking place in Africa over the mining of the diamond. diamonds are formed at a a depth of about 100km (60 miles) down in the mantle of the earth. The diamond itself is a crystallized carbon, which in fact is the hardest known substance on earth. What this means is that a diamond can scratch anything. But then in a moment of great violence, magama and diamonds are thrust up toward the surface through a conduit called a kimberlite pipe. The name kimberlite comes from a town in Africa, Kimberly. Many of these pipes exist in South Africa, but recently, many have been discovered in Brazil and even Canada! The pipes themselves are not very interesting, but as you can see from the diagram, the diamonds are located throughout the pipe- and that is of course what we are all interested in.
The pipe is then mined, and the raw diamonds are found. The diamonds are so valueable that the mining companies often justify the processing of large amounts of rock just to get a few diamonds.
These raw diamonds are then cut to form the many cuts that we enjoy today. I personally like the brilliant cut, below is a guide of how to facet the diamonds:
Tuesday, December 4, 2007
Tectonic subduction and what it means for you.
I will preface this post with a very brief overview of a fascinating geological process. Lets start with a cross section of the earth.
Beneath our feet, as most of us know, are several large layers of rock, magma, and core materials. (see picture above)...
Our planet, on in its surface, is broken up into large pieces called tectonic plates. Over the course of millions of years, these plates have shifted around to create the continents as we now currently know them.
These processes still continue today, and for the most part are a large cause of many of the earthquakes and volcanoes that we experience today. Along the boundaries of these plates there are different movements that they make. At some locations, plates collide, at others they get pushed apart, and at others they grind past each other. The collisional boundary is called a subduction zone when one plate gets pushed beneath another and eventually is forced back into the mantle and is re-melted. The boundary where the plates get pushed apart is called a divergent plate boundary (and where this occurs in the ocean, it called a mid-ocean ridge).
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Here is a diagram explaining these processes in a greater detail.
Hopefully that made sense. Lets take that bit of knowledge and apply it to the really cool part.
Off the coast of Washington, Oregon, and Northern California is a small tectonic plate called the Juan De Fuca Plate. This plate has been colliding with the North American Plate for the past several millions of years (however, it used to be called the Farralon plate). As the plate is getting thrust down into the earth, it goes deeper into the mantle. Obviously this heats it up quite a bit and re-melts some of the crust. That melted crust is then forced upward and becomes the volcanoes that we have in that part of the country.
I like this diagram a lot better...
That is why there are all of the volcanoes in the Pacific Northwest. The magma being erupted is re-melted crust that was initially made out at sea. Isn't it amazing how mother nature recycles herself???
Ok, so essentially you have an area that makes oceanic crust (a mid ocean ridge) and another that consumes it (a subduction zone). I wonder what would happen if the two were to collide? The answer to that is rather simple arithmetic. 1 + (-1) = 0. Such an event DID happen, and that is why we have the San Andreas Fault.
Read on...
"EVOLUTION OF THE SAN ANDREAS FAULT.
This series of block diagrams shows how the subduction zone along the west coast of North America transformed into the San Andreas Fault from 30 million years ago to the present. Starting at 30 million years ago, the westward- moving North American Plate began to override the spreading ridge between the Farallon Plate and the Pacific Plate. This action divided the Farallon Plate into two smaller plates, the northern Juan de Fuca Plate (JdFP) and the southern Cocos Plate (CP). By 20 million years ago, two triple junctions began to migrate north and south along the western margin of the West Coast. (Triple junctions are intersections between three tectonic plates; shown as red triangles in the diagrams.) The change in plate configuration as the North American Plate began to encounter the Pacific Plate resulted in the formation of the San Andreas Fault. The northern Mendicino Triple Junction (M) migrated through the San Francisco Bay region roughly 12 to 5 million years ago and is presently located off the coast of northern California, roughly midway between San Francisco (SF) and Seattle (S). The Mendicino Triple Junction represents the intersection of the North American, Pacific, and Juan de Fuca Plates. The southern Rivera Triple Junction (R) is presently located in the Pacific Ocean between Baja California (BC) and Manzanillo, Mexico (MZ). Evidence of the migration of the Mendicino Triple Junction northward through the San Francisco Bay region is preserved as a series of volcanic centers that grow progressively younger toward the north. Volcanic rocks in the Hollister region are roughly 12 million years old whereas the volcanic rocks in the Sonoma-Clear Lake region north of San Francisco Bay range from only few million to as little as 10,000 years old. Both of these volcanic areas and older volcanic rocks in the region are offset by the modern regional fault system."
"Map of the modern San Andreas Fault in relation to the greater plate-tectonic setting of western North America and the northeastern Pacific Ocean basin. The San Andreas Fault represents a great transform-fault boundary between the North American Plate and the Pacific Plate. The San Andreas Fault system connects between spreading centers in the East Pacific Rise (to the south) and the Juan de Fuca Ridge and Mendicino fracture zone system (to the north). The San Andreas Fault system has gradually evolved since middle Tertiary time (beginning about 28 million years ago). The right-lateral offset that has occurred on the fault system since that time is about 282 miles (470 km); however, the fault system consists of many strands that have experienced different amounts of offset."
So that brings us up to today. What will happen in the next few million years? Well, if everything keeps going at the rate its going, the JdF Plate will eventually be consumed and the San Andreas fault will continue unabated north up to Alaska. Of course all of the continent on the pacific plate (ie. Western Cali, Oregon, and Washington) will be making a slow journey north, detaching themselves from the rest of the Continent)
So, to answer Dad and Ethan's question...I'm of the opinion that the long term earthquakes that the last post is in reference to is earthquakes caused by the subduction of the Juan deFuca Plate under Washington and Oregon. These long-term quakes don't make the area any more safe than they would be otherwise. You live on the top of a huge conveyor belt that is always moving, eventually it will snag. Not necessarily all at once, but parts here and there will get stuck and then you'll have your large earthquakes.. Here is a diagram as evidence for my theory:
What this shows is a plot of earthquake location and depth. It is a cross section, with the top being the surface. That nice pattern of dots the arcs gracefully off to the lower left is the actual plate being forced down. this subduction is not a stop-and-go procedure, but a slow, ever-moving event.
Beneath our feet, as most of us know, are several large layers of rock, magma, and core materials. (see picture above)...
Our planet, on in its surface, is broken up into large pieces called tectonic plates. Over the course of millions of years, these plates have shifted around to create the continents as we now currently know them.
These processes still continue today, and for the most part are a large cause of many of the earthquakes and volcanoes that we experience today. Along the boundaries of these plates there are different movements that they make. At some locations, plates collide, at others they get pushed apart, and at others they grind past each other. The collisional boundary is called a subduction zone when one plate gets pushed beneath another and eventually is forced back into the mantle and is re-melted. The boundary where the plates get pushed apart is called a divergent plate boundary (and where this occurs in the ocean, it called a mid-ocean ridge).
_gif.jpg)
Here is a diagram explaining these processes in a greater detail.Hopefully that made sense. Lets take that bit of knowledge and apply it to the really cool part.
Off the coast of Washington, Oregon, and Northern California is a small tectonic plate called the Juan De Fuca Plate. This plate has been colliding with the North American Plate for the past several millions of years (however, it used to be called the Farralon plate). As the plate is getting thrust down into the earth, it goes deeper into the mantle. Obviously this heats it up quite a bit and re-melts some of the crust. That melted crust is then forced upward and becomes the volcanoes that we have in that part of the country.
I like this diagram a lot better...
That is why there are all of the volcanoes in the Pacific Northwest. The magma being erupted is re-melted crust that was initially made out at sea. Isn't it amazing how mother nature recycles herself???
Ok, so essentially you have an area that makes oceanic crust (a mid ocean ridge) and another that consumes it (a subduction zone). I wonder what would happen if the two were to collide? The answer to that is rather simple arithmetic. 1 + (-1) = 0. Such an event DID happen, and that is why we have the San Andreas Fault.
Read on...
"EVOLUTION OF THE SAN ANDREAS FAULT.
This series of block diagrams shows how the subduction zone along the west coast of North America transformed into the San Andreas Fault from 30 million years ago to the present. Starting at 30 million years ago, the westward- moving North American Plate began to override the spreading ridge between the Farallon Plate and the Pacific Plate. This action divided the Farallon Plate into two smaller plates, the northern Juan de Fuca Plate (JdFP) and the southern Cocos Plate (CP). By 20 million years ago, two triple junctions began to migrate north and south along the western margin of the West Coast. (Triple junctions are intersections between three tectonic plates; shown as red triangles in the diagrams.) The change in plate configuration as the North American Plate began to encounter the Pacific Plate resulted in the formation of the San Andreas Fault. The northern Mendicino Triple Junction (M) migrated through the San Francisco Bay region roughly 12 to 5 million years ago and is presently located off the coast of northern California, roughly midway between San Francisco (SF) and Seattle (S). The Mendicino Triple Junction represents the intersection of the North American, Pacific, and Juan de Fuca Plates. The southern Rivera Triple Junction (R) is presently located in the Pacific Ocean between Baja California (BC) and Manzanillo, Mexico (MZ). Evidence of the migration of the Mendicino Triple Junction northward through the San Francisco Bay region is preserved as a series of volcanic centers that grow progressively younger toward the north. Volcanic rocks in the Hollister region are roughly 12 million years old whereas the volcanic rocks in the Sonoma-Clear Lake region north of San Francisco Bay range from only few million to as little as 10,000 years old. Both of these volcanic areas and older volcanic rocks in the region are offset by the modern regional fault system."
"Map of the modern San Andreas Fault in relation to the greater plate-tectonic setting of western North America and the northeastern Pacific Ocean basin. The San Andreas Fault represents a great transform-fault boundary between the North American Plate and the Pacific Plate. The San Andreas Fault system connects between spreading centers in the East Pacific Rise (to the south) and the Juan de Fuca Ridge and Mendicino fracture zone system (to the north). The San Andreas Fault system has gradually evolved since middle Tertiary time (beginning about 28 million years ago). The right-lateral offset that has occurred on the fault system since that time is about 282 miles (470 km); however, the fault system consists of many strands that have experienced different amounts of offset."
So that brings us up to today. What will happen in the next few million years? Well, if everything keeps going at the rate its going, the JdF Plate will eventually be consumed and the San Andreas fault will continue unabated north up to Alaska. Of course all of the continent on the pacific plate (ie. Western Cali, Oregon, and Washington) will be making a slow journey north, detaching themselves from the rest of the Continent)
So, to answer Dad and Ethan's question...I'm of the opinion that the long term earthquakes that the last post is in reference to is earthquakes caused by the subduction of the Juan deFuca Plate under Washington and Oregon. These long-term quakes don't make the area any more safe than they would be otherwise. You live on the top of a huge conveyor belt that is always moving, eventually it will snag. Not necessarily all at once, but parts here and there will get stuck and then you'll have your large earthquakes.. Here is a diagram as evidence for my theory:
What this shows is a plot of earthquake location and depth. It is a cross section, with the top being the surface. That nice pattern of dots the arcs gracefully off to the lower left is the actual plate being forced down. this subduction is not a stop-and-go procedure, but a slow, ever-moving event.
Monday, December 3, 2007
RISING TIDES INTENSIFY NON-VOLCANIC TREMOR IN EARTH'S CRUST
Ooh, this is worth a post and discussion... It comes from the NASA Earth Observatory (who, by the way, has an image lab on the same floor as the geology department at ASU. The original page can be found here: http://earthobservatory.nasa.gov/Newsroom/MediaAlerts/2007/2007112225969.html)
For more than a decade geoscientists have detected what amount to ultra-slow-motion earthquakes under Western Washington and British Columbia on a regular basis, about every 14 months. Such episodic tremor-and-slip events typically last two to three weeks and can release as much energy as a large earthquake, though they are not felt and cause no damage.
Now University of Washington researchers have found evidence that these slow-slip events are actually affected by the rise and fall of ocean tides.
"There has been some previous evidence of the tidal effect, but the detail is not as great as what we have found," said Justin Rubinstein, a UW postdoctoral researcher in Earth and space sciences.
And while previous research turned up suggestions of a tidal pulse at 12.4 hours, this is the first time that a second pulse, somewhat more difficult to identify, emerged in the evidence at intervals of 24 to 25 hours, he said.
Rubinstein is lead author of a paper that provides details of the findings, published Nov. 22 in Science Express, the online edition of the journal Science. Co-authors are Mario La Rocca of the Istituto Nazionale di Geofisica e Vulcanologia in Italy, and John Vidale, Kenneth Creager and Aaron Wech of the UW.
The most recent tremor-and-slip events in Washington and British Columbia took place in July 2004, September 2005 and January 2007. Before each, researchers deployed seismic arrays, each containing five to 11 separate seismic monitoring stations, to collect more accurate information about the location and nature of the tremors. Four of the arrays were placed on the Olympic Peninsula in Washington and the fifth was on Vancouver Island in British Columbia.
The arrays recorded clear twice-a-day pulsing in the 2004 and 2007 episodes, and similar pulsing occurred in 2005 but was not as clearly identified. The likely source from tidal stresses, the researchers said, would be roughly once- and twice-a-day pulses from the gravitational influence of the sun and moon. The clearest tidal pulse at 12.4 hours coincided with a peak in lunar forcing, while the pulse at 24 to 25 hours was linked to peaks in both lunar and solar influences.
The rising tide appeared to increase the tremor by a factor of 30 percent, though the Earth distortion still was so small that it was undetectable without instruments, said Vidale, a UW professor of Earth and space sciences and director of the Pacific Northwest Seismograph Network.
"We expected that the added water of a rising tide would clamp down on the tremor, but it seems to have had the opposite effect. It's fair to say that we don't understand it," Vidale said.
"Earthquakes don't behave this way," he added. "Most don't care whether the tide is high or low."
The researchers were careful to rule out noise that might have come from human activity. For instance, one of the arrays was near a logging camp and another was near a mine.
"It's pretty impressive how strong a signal those activities can create," Rubinstein said, adding that the slow-slip pulses were recorded when those human activities were at a minimum.
For more than a decade geoscientists have detected what amount to ultra-slow-motion earthquakes under Western Washington and British Columbia on a regular basis, about every 14 months. Such episodic tremor-and-slip events typically last two to three weeks and can release as much energy as a large earthquake, though they are not felt and cause no damage.
Now University of Washington researchers have found evidence that these slow-slip events are actually affected by the rise and fall of ocean tides.
"There has been some previous evidence of the tidal effect, but the detail is not as great as what we have found," said Justin Rubinstein, a UW postdoctoral researcher in Earth and space sciences.
And while previous research turned up suggestions of a tidal pulse at 12.4 hours, this is the first time that a second pulse, somewhat more difficult to identify, emerged in the evidence at intervals of 24 to 25 hours, he said.
Rubinstein is lead author of a paper that provides details of the findings, published Nov. 22 in Science Express, the online edition of the journal Science. Co-authors are Mario La Rocca of the Istituto Nazionale di Geofisica e Vulcanologia in Italy, and John Vidale, Kenneth Creager and Aaron Wech of the UW.
The most recent tremor-and-slip events in Washington and British Columbia took place in July 2004, September 2005 and January 2007. Before each, researchers deployed seismic arrays, each containing five to 11 separate seismic monitoring stations, to collect more accurate information about the location and nature of the tremors. Four of the arrays were placed on the Olympic Peninsula in Washington and the fifth was on Vancouver Island in British Columbia.
The arrays recorded clear twice-a-day pulsing in the 2004 and 2007 episodes, and similar pulsing occurred in 2005 but was not as clearly identified. The likely source from tidal stresses, the researchers said, would be roughly once- and twice-a-day pulses from the gravitational influence of the sun and moon. The clearest tidal pulse at 12.4 hours coincided with a peak in lunar forcing, while the pulse at 24 to 25 hours was linked to peaks in both lunar and solar influences.
The rising tide appeared to increase the tremor by a factor of 30 percent, though the Earth distortion still was so small that it was undetectable without instruments, said Vidale, a UW professor of Earth and space sciences and director of the Pacific Northwest Seismograph Network.
"We expected that the added water of a rising tide would clamp down on the tremor, but it seems to have had the opposite effect. It's fair to say that we don't understand it," Vidale said.
"Earthquakes don't behave this way," he added. "Most don't care whether the tide is high or low."
The researchers were careful to rule out noise that might have come from human activity. For instance, one of the arrays was near a logging camp and another was near a mine.
"It's pretty impressive how strong a signal those activities can create," Rubinstein said, adding that the slow-slip pulses were recorded when those human activities were at a minimum.
Monday, November 19, 2007
Thursday, November 15, 2007
Wednesday, November 14, 2007
Earthquakes 101
There seems to be some confusion about earthquakes, and our associated risks with them. It is easy to watch the news and see the devistation that takes place somewhere else in the world, and worry that it will happen in our own backyard. If you live on the west coast, namely southern california, this may be very true, but for those of us elsewhere this may or may not be the case.
How an earthquake happens:
Simplistically, an earthquake happens when two large rocks slide past each other. This suture between the two rocks is called a fault. Faults range in size from a meter, to hundereds even thousands of kilometers in legnth. What causes an earthquake? It is when pressure builds up between the rocks and something gives suddenly. The point at where this happens is called the hypocenter. Often, earthquakes happen deep underground. Today's earthquake in Chile took place 60 km under the earth. The term epicenter refers to the location on the surface abouve the hypocenter. Kinda like "x marks the spot", and the earthquake itself is the treasure.
Am I at risk for an earthquake?
Well, here is a earthquake hazard map for the US. You be the judge.
With regards to todays earthquake in Chile, and any potential hazard that me and my family has by living in Phoenix:
When an earthquake happens, there are 2 types of seismic waves generated. The first is called a P wave. it is compressional much like sound is going through air. This however travels through the earth and speeds much faster than sound though. the 2nd type and the dangerous type is called a S wave. It is like the kind of wave where you make a wave in a streched out rope or wire. It is dangerous because of it's shear. it moves from side to side, and that what causes the damage. S waves dissapate quickly (see the USGS shake map), the p waves traveled from chile to both AZ an NH in about 20 minutes, then reverberated inside the earth for about 4 hours. The seismogram reading is essentially like putting a microphone in the earth and listening to it grumble. This earthquake, because of its magnitude, was a loud grumble. There are quiet grumbles too, like mining explosions, or large trucks driving near the seismogram.
Hopefully this all helps.
How an earthquake happens:
Simplistically, an earthquake happens when two large rocks slide past each other. This suture between the two rocks is called a fault. Faults range in size from a meter, to hundereds even thousands of kilometers in legnth. What causes an earthquake? It is when pressure builds up between the rocks and something gives suddenly. The point at where this happens is called the hypocenter. Often, earthquakes happen deep underground. Today's earthquake in Chile took place 60 km under the earth. The term epicenter refers to the location on the surface abouve the hypocenter. Kinda like "x marks the spot", and the earthquake itself is the treasure.
Am I at risk for an earthquake?
Well, here is a earthquake hazard map for the US. You be the judge.
With regards to todays earthquake in Chile, and any potential hazard that me and my family has by living in Phoenix:
When an earthquake happens, there are 2 types of seismic waves generated. The first is called a P wave. it is compressional much like sound is going through air. This however travels through the earth and speeds much faster than sound though. the 2nd type and the dangerous type is called a S wave. It is like the kind of wave where you make a wave in a streched out rope or wire. It is dangerous because of it's shear. it moves from side to side, and that what causes the damage. S waves dissapate quickly (see the USGS shake map), the p waves traveled from chile to both AZ an NH in about 20 minutes, then reverberated inside the earth for about 4 hours. The seismogram reading is essentially like putting a microphone in the earth and listening to it grumble. This earthquake, because of its magnitude, was a loud grumble. There are quiet grumbles too, like mining explosions, or large trucks driving near the seismogram.
Hopefully this all helps.
Magnitude 7.7 Earthquake in Chile
Holy cow, this one is HUGE. Here is a shot of a seismogram here in Arizona. This is how much shaking we have had!
Here is another seismogram reading about 2 hours later, its still going!
Let me give you some background so you know kinda what you are looking at. This is a seismogram readout from a seismometer located in Tucson. It records shaking in the earth. Most of the readouts on this machine are totally unfelt be humans, but the sensitivity of the machine is such that it picks up vibrational waves as they pass by. The earthquake was powerful enough in Chile to be very strongly noticed by the machines. There is resonant readings as the waves reflect within the earth. Kinda like when you splash in a pool of water. Although you might not be right next to someone who is splashing, you can see waves caused by it go by, and then as the waves reflect off the sides of the pool and go by again.
Here is an intensity map of the earthquake from the USGS:
Here is another seismogram reading about 2 hours later, its still going!
Let me give you some background so you know kinda what you are looking at. This is a seismogram readout from a seismometer located in Tucson. It records shaking in the earth. Most of the readouts on this machine are totally unfelt be humans, but the sensitivity of the machine is such that it picks up vibrational waves as they pass by. The earthquake was powerful enough in Chile to be very strongly noticed by the machines. There is resonant readings as the waves reflect within the earth. Kinda like when you splash in a pool of water. Although you might not be right next to someone who is splashing, you can see waves caused by it go by, and then as the waves reflect off the sides of the pool and go by again.
Here is an intensity map of the earthquake from the USGS:
Sunday, November 11, 2007
Fossils
Due to an overwhelming response, here is my fossil collection:
This first photo is a collection of crinoid stems in a piece of weathered Redwall Limestone. The crinoid heads are missing, but the stems are nicely preserved because of their calcium carbonate pieces. those guys are about 335 million years old. The limestone that they are found in is one of the larger rock layers found at the Grand Canyon.
This next photo is a storm segment from the Naco formation. There are a least 3 different types of fossils in this piece. Can you find them? The twig looking ones are fossilized bryozoan, a moss-like creature. There are also crinoid stem segments, and a couple of clam-like shells
This picture shows an assortment of other fossils also from the Naco formation. There are (from left to right) a couple of clam-like fossils, crinoid stem segments, saved entirely in 3D (the little barrel shaped guys), a streched spiral gastropod (found in the Upper Iowa River neah Decorah, IA), and a few intact brachiopods. The difference between the brachiopods and the clam like ones is that the clam like ones (they have a technical name but i cant seem to remember what it is) are symmetrical through the suture, and the brachiopods' symmetry is perpendicular to the suture line. Here is a close up of the clam like ones...
This first photo is a collection of crinoid stems in a piece of weathered Redwall Limestone. The crinoid heads are missing, but the stems are nicely preserved because of their calcium carbonate pieces. those guys are about 335 million years old. The limestone that they are found in is one of the larger rock layers found at the Grand Canyon.
This next photo is a storm segment from the Naco formation. There are a least 3 different types of fossils in this piece. Can you find them? The twig looking ones are fossilized bryozoan, a moss-like creature. There are also crinoid stem segments, and a couple of clam-like shells
This picture shows an assortment of other fossils also from the Naco formation. There are (from left to right) a couple of clam-like fossils, crinoid stem segments, saved entirely in 3D (the little barrel shaped guys), a streched spiral gastropod (found in the Upper Iowa River neah Decorah, IA), and a few intact brachiopods. The difference between the brachiopods and the clam like ones is that the clam like ones (they have a technical name but i cant seem to remember what it is) are symmetrical through the suture, and the brachiopods' symmetry is perpendicular to the suture line. Here is a close up of the clam like ones...
Tuesday, November 6, 2007
Papago Park
I visited another local park here in Phoenix today. Its called Papago (pap-a-go) Park. It is located not far from ASU, but has some very interesting geology.
This perticular butte is fascinating to many people for mostly non-geological reasons. It has a hole in it that when standing in offers spectacular vistas of downtown. Anyway, the history of the rock. Formed at the same time as Hayden Butte, Hole-in-the-rock (thats actually its proper name) is formed from totally different processes. 17 million years ago, somewhere within 2 km or so, there once stood a mountain fromed from granite and quartzite. One very violent day there was a massive landslide that came off the mountain and headed toward an ancient river. The landslice eventually became lithofied (turned into stone) and formed the butte. Interesting enough, the mountain that formed the landslide had eroded completely and cannot be found anymore. The butte is composed out of a composite sedimentary rock called breccia (bretch-a) which is an amalgamation of mud, sand , and broken up parts of granite and quatrzite (all of which came from the parent mountain) some of the chunks of granite are as large as a house.
The holes in the rock were formed when these boulders fell out of the breccia, and then were exposed to what is called cavernous erosion. This erosion over the course of millions of years formed the caves that so many people enjoy today. On an even more interesting note, this butte has the Great Unconformity running right through it! Remember from my trip up to payson, how where was the section of 1.2 billion years missing. Well that same gap exists at the base of the butte. The base of the butte is made up of granite that is 1.8 billion years old (as old as the oldest rocks found at the bottom of the Grand Canyon). however i found a xenolith of some kinda ash metamorphic that is even older. I had to take a sample of that back for my collection (as oldest rock)
This perticular butte is fascinating to many people for mostly non-geological reasons. It has a hole in it that when standing in offers spectacular vistas of downtown. Anyway, the history of the rock. Formed at the same time as Hayden Butte, Hole-in-the-rock (thats actually its proper name) is formed from totally different processes. 17 million years ago, somewhere within 2 km or so, there once stood a mountain fromed from granite and quartzite. One very violent day there was a massive landslide that came off the mountain and headed toward an ancient river. The landslice eventually became lithofied (turned into stone) and formed the butte. Interesting enough, the mountain that formed the landslide had eroded completely and cannot be found anymore. The butte is composed out of a composite sedimentary rock called breccia (bretch-a) which is an amalgamation of mud, sand , and broken up parts of granite and quatrzite (all of which came from the parent mountain) some of the chunks of granite are as large as a house.
The holes in the rock were formed when these boulders fell out of the breccia, and then were exposed to what is called cavernous erosion. This erosion over the course of millions of years formed the caves that so many people enjoy today. On an even more interesting note, this butte has the Great Unconformity running right through it! Remember from my trip up to payson, how where was the section of 1.2 billion years missing. Well that same gap exists at the base of the butte. The base of the butte is made up of granite that is 1.8 billion years old (as old as the oldest rocks found at the bottom of the Grand Canyon). however i found a xenolith of some kinda ash metamorphic that is even older. I had to take a sample of that back for my collection (as oldest rock)
Sunday, November 4, 2007
Payson
Yesterday we took a great field trip to see some cool rocks about 2.5 hours north east of Phoenix. These rocks are at the southwestern edge of what is called the Matzatzal Province. The Matzatzal province is the oldest rocks layer found in Arizona, ranging between 1.6-1.8 Ga, this layer is represented in the Grand Canyon as Vishnu Schist.
Here at stop #1, you can see the basement rock layer for our study, the Payson granite. The layer right above the granite is the Tapeats Sandstone (also represented at the GC). Whats amazing here is what is called the great unconformity. To the untrained eye, theese rock layers look like a normal transition, or juust like the same rock alltogether. But the bottom layer is 1.2 billion years older than the top layer (540 million years old.) What this means is that there is 1.2 billion years of rock history that is entirely gone.
Here is one of my professors (Dr. Stump) explaining some of the finer details of the strata (strata means column of rocks).
Here is another shot of the rocks:
A little farther up the section we came to the disconformity between the Redwall Limestone and the Naco Formation. The Naco is the layer on the top of the road-cut, whilst the Redwall is the bottom layers:
Here are some other views of the two groups. Can you see the division??
The Naco formation is LOADED with fossils! We took 60 minutes to sample and log some (which we also got to keep for our personal collections) I found about 30 or so in that time. Ranging from crinoids to brachiopods, there were some sweet samples! Ask me sometime and I'll post close-up's of the different ones. I also founs a cool sample that has criniods, brachiopods and fossilized bryozoans. These fossils are all form the Pennsylvanian period so they are about 300 million years old.
Here is a scenery shot of what the forests look like up there:
Here is a self portrait of me as I an taking notes:
There are more scenery shots. One of them is our group sitting at the top of the main section of Coconino Sandstone.
Here is one last shot of the group hiking to a remote locaton to look at a sample of the Apache Group formation, and then the Apache Group Formation itself.
Here at stop #1, you can see the basement rock layer for our study, the Payson granite. The layer right above the granite is the Tapeats Sandstone (also represented at the GC). Whats amazing here is what is called the great unconformity. To the untrained eye, theese rock layers look like a normal transition, or juust like the same rock alltogether. But the bottom layer is 1.2 billion years older than the top layer (540 million years old.) What this means is that there is 1.2 billion years of rock history that is entirely gone.
Here is one of my professors (Dr. Stump) explaining some of the finer details of the strata (strata means column of rocks).
Here is another shot of the rocks:
A little farther up the section we came to the disconformity between the Redwall Limestone and the Naco Formation. The Naco is the layer on the top of the road-cut, whilst the Redwall is the bottom layers:
Here are some other views of the two groups. Can you see the division??
The Naco formation is LOADED with fossils! We took 60 minutes to sample and log some (which we also got to keep for our personal collections) I found about 30 or so in that time. Ranging from crinoids to brachiopods, there were some sweet samples! Ask me sometime and I'll post close-up's of the different ones. I also founs a cool sample that has criniods, brachiopods and fossilized bryozoans. These fossils are all form the Pennsylvanian period so they are about 300 million years old.
Here is a scenery shot of what the forests look like up there:
Here is a self portrait of me as I an taking notes:
There are more scenery shots. One of them is our group sitting at the top of the main section of Coconino Sandstone.
Here is one last shot of the group hiking to a remote locaton to look at a sample of the Apache Group formation, and then the Apache Group Formation itself.
Saturday, October 27, 2007
Phoenix, a brief history.
Todays little jaunt was pretty fun. I took James along and so we both got to learn all sorts of cool geology stuff. I am taking notes from Emily's last comment and will be "dumbing down" my blogs so that they are easier to understand.
This morning's trip was down to a place called South Mountain. South Mountain is a prominent feature of the Phoenician skyline. In fact, it can be seen from just about anywhere in the valley. It is most easily identified as the mountain that has all of the antennas on it. Anyway, I have known about south mountain for about as long as I have lived here in phoenix. However, this trip was remarkably interesting because it really opened my eyes to the great geological history that I live on top of. Here is an aerial of where we met:
This location, as it turn out is quite unique. It is the juncture of 1700 million year old gneiss and 22 million year old granite.(geologists use the term Ga, an acronym for giga-annum, which is latin for "billion years". I will use the abbreviation Ga for billion years old, and Ma for million years old from this point on.) Anyway, what happened is a LONG time ago, more than seventeen hundred million years ago rocks were formed through various means. Over the millions of years, and at a depth of about 10km under the surface, these rocks were heated and deformed. This intense pressure and heat transformed, or more appropriately, metamorphosed these rocks into the gneiss that is now found at the surface. Fast forward to 22 million years ago, a large plume of hot magma from deep within the earth is ejected and intrudes the gneiss. When the rock cools, it becomes granite.
Here is another view of the boundry:
Up to this point things have been relatively dull. All of this activity takes place 10km underground. On the surface, life is flourishing. It is early in the Cenozoic era. Then something rather catastrophic happens. There is an series of earthquakes. Huge earthquakes! To give you an idea of just how big these quakes were think about this. The typical earthquake in california, for example the 1989 Loma Prieta quake (you know the one that happened during the world series that year?) made the earth move only a couple of meters. They call this movement displacement. Anyway, the series of quakes, which can be called rifting, displaced this mountain by more than 40Km. Here is another aerial image of how far that is:
Incredible, if you ask me. The south mountain range used to be homogeneous with the McDowell Range. The big gray area in between the ranges is metro Phoenix.
Well, next week will take me to Payson, AZ in the search of mississippian fossils.
This morning's trip was down to a place called South Mountain. South Mountain is a prominent feature of the Phoenician skyline. In fact, it can be seen from just about anywhere in the valley. It is most easily identified as the mountain that has all of the antennas on it. Anyway, I have known about south mountain for about as long as I have lived here in phoenix. However, this trip was remarkably interesting because it really opened my eyes to the great geological history that I live on top of. Here is an aerial of where we met:
This location, as it turn out is quite unique. It is the juncture of 1700 million year old gneiss and 22 million year old granite.(geologists use the term Ga, an acronym for giga-annum, which is latin for "billion years". I will use the abbreviation Ga for billion years old, and Ma for million years old from this point on.) Anyway, what happened is a LONG time ago, more than seventeen hundred million years ago rocks were formed through various means. Over the millions of years, and at a depth of about 10km under the surface, these rocks were heated and deformed. This intense pressure and heat transformed, or more appropriately, metamorphosed these rocks into the gneiss that is now found at the surface. Fast forward to 22 million years ago, a large plume of hot magma from deep within the earth is ejected and intrudes the gneiss. When the rock cools, it becomes granite.
Here is another view of the boundry:
Up to this point things have been relatively dull. All of this activity takes place 10km underground. On the surface, life is flourishing. It is early in the Cenozoic era. Then something rather catastrophic happens. There is an series of earthquakes. Huge earthquakes! To give you an idea of just how big these quakes were think about this. The typical earthquake in california, for example the 1989 Loma Prieta quake (you know the one that happened during the world series that year?) made the earth move only a couple of meters. They call this movement displacement. Anyway, the series of quakes, which can be called rifting, displaced this mountain by more than 40Km. Here is another aerial image of how far that is:
Incredible, if you ask me. The south mountain range used to be homogeneous with the McDowell Range. The big gray area in between the ranges is metro Phoenix.
Well, next week will take me to Payson, AZ in the search of mississippian fossils.
Wednesday, October 17, 2007
Hayden Butte Revisited
Back to the butte. Tuesday took us back to Hayden butte, but this time to stratorgaph the lower sedimentation layers (notably from the base up to the ash layer from the superstition caldera eruptions. This lab took a bit longer than usual, however it was great to get up close and personal with various rock outcropping. Generally speaking, the bedding we looked at consisted of about 70 layers of alternating sandstone and shale. Only 3 of of the layers contained trace fossils. The oldest layer had trace fossils of worm burrows, which was again repeated in a layer about 10 meters above. The other trace was the mudcracks. Upon closer inspection it appears that the mud cracks formed on several sandstone layers in superpositioned horizons, in my estimations there were 4 distinct horizons that them. I'm gonna try and get a scan or two of the hand drawn stratographic sections that we did (about 6 pages in all). I'm looking forward to Oct 27, when we will be on a fieldtrip to south mountain to checkout some sweet synclinic action. ohh yeah.
In a lighter note, I really enjoy the names geologists come up with for things. For example gneiss (pronounced nice) is a common metamorphic rock. Schist is another common metamorphic rock. Anyway there are many others with strange and unusual names. But i couldn't leave these two alone. So i came up with an idea for a t-shirt:
In a lighter note, I really enjoy the names geologists come up with for things. For example gneiss (pronounced nice) is a common metamorphic rock. Schist is another common metamorphic rock. Anyway there are many others with strange and unusual names. But i couldn't leave these two alone. So i came up with an idea for a t-shirt:
Tuesday, October 9, 2007
Hayden Butte Lab
This is the first outdoor lab for the historical geology class. Located on ASU Campus, Hayden Butte (A Mountain) is a well known site for and ASU student. The butte holds the Sun Devil Stadium (Home of ASU Football and Super Bowl XXX) on a saddle on the south east side. The lab began by looking at the oldest rocks on the butte, located on the north side in a drainage canal parallel to Rio Salado Pky. The exposed sandstone layers here are estimated to be only 17 Ma. The oldest sandstone beds are perforated with trace worm burrow fossils.
Just up the rock strata we found:
This is the trace fossil of mud cracks. Cracks were formed into a layer of mud, that has since turned into shale. Sand filled the cracks and formed a layer of sandstone. Later, the underlying shale eroded and left the negative impression of the cracked mud.
A little farther up the strata we found:
This section of Sandstone / Shale Interbedding shows a fault. Although the age of the fault is unknown, is can be assumed that it was caused by the tilting event.
Now this was unusual:
This is a very perculeier formation. What this is is a 2m thick volcanic ash formation. However as you can see, the bedding has been convoluted into ball and pillow shapes. This can be caused by either seismic activity on the wet rock, or by being compressed from above (also while the rock was still wet. This formation was so cool that I had to grab a smaple for my collection.
Finally the youngest rocks on the butte were a nice andesite lava flow. A short ways down from the top I found some eroded chunks of the andesite:
and here is what I thought was really cool; this is where a lava flowed over sandstone, resulting in contact metamorphisim:
And here is a rip-up clast of sandstone that had been metamorphosed into quartzite:
Just up the rock strata we found:
This is the trace fossil of mud cracks. Cracks were formed into a layer of mud, that has since turned into shale. Sand filled the cracks and formed a layer of sandstone. Later, the underlying shale eroded and left the negative impression of the cracked mud.
A little farther up the strata we found:
This section of Sandstone / Shale Interbedding shows a fault. Although the age of the fault is unknown, is can be assumed that it was caused by the tilting event.
Now this was unusual:
This is a very perculeier formation. What this is is a 2m thick volcanic ash formation. However as you can see, the bedding has been convoluted into ball and pillow shapes. This can be caused by either seismic activity on the wet rock, or by being compressed from above (also while the rock was still wet. This formation was so cool that I had to grab a smaple for my collection.
Finally the youngest rocks on the butte were a nice andesite lava flow. A short ways down from the top I found some eroded chunks of the andesite:
and here is what I thought was really cool; this is where a lava flowed over sandstone, resulting in contact metamorphisim:
And here is a rip-up clast of sandstone that had been metamorphosed into quartzite:
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