Archive for the GEOLOGY Category

New Seafloor Map Reveals Secrets of Ancient Continents’ Shoving Match

Posted in GEOLOGY with tags on January 21, 2016 by 2eyeswatching

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New Seafloor Map Reveals Secrets of Ancient Continents’ Shoving Match

El Morro: Stunning Photos of New Mexico’s Sandstone Bluff

Posted in GEOLOGY with tags on January 21, 2016 by 2eyeswatching

Post 5034

El Morro: Stunning Photos of New Mexico’s Sandstone Bluff

Here’s the Most Complete Ocean Floor Map Ever Made

Posted in GEOLOGY with tags on December 30, 2015 by 2eyeswatching

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Here’s the Most Complete Ocean Floor Map Ever Made

Here's the Most Complete Ocean Floor Map Ever Made

What lies beneath the deep blue sea? So much more than you might think.

The results that let this new, marvelously-detailed map of the seafloor fromNASA’s Earth Observatory be made were actually first published last year as part of a paper in Science from researchers at NOAA and Scripps Institution of Oceanography. They were also made available in a series of area maps and even as a Google Earth interactive. This latest incarnation, though, offers—in a single glance—perhaps the most complete unified view of the Earth’s seafloor to date, showing not just the mountains beneath the water, but also the crevices cracking the watery ground.

The detail of the map is particularly impressive. Not only does it show features that had previously not been seen, it’s also capable of catching any feature larger than 5 kilometers, which has been especially good for capturing some of the smaller ridge features.

It’s not just the map itself that’s interesting, though—it’s how they finally managed to make it.

Here's the Most Complete Ocean Floor Map Ever Made

So, how do you map what you can’t see?

Typically, finely-wrought ocean maps have been the result of extensive sonar. This is expensive and time-consuming, so sonar maps are mostly only made of places where ships spend the most time. The problem with that approach is that our oceans are vast and ships are small—meaning only a tiny percentage of the ocean floor (between 5 – 15 percent, NASA estimates) was mapped.

So, instead of depending on sonar, researchers looked to something else: Gravity. Using existing satellite data of the ocean, researchers searched for gravity anomalies as measured by sea surface heights. Where gravity was slightly stronger (those red/orange areas), they found mountains rising upwards, in the weaker areas (those blue patches) they were deep cracks.

This isn’t the first time researchers have made use of gravity as a measurement tool. A similar method has been used in the past to measure changes to ice cover in the Antarctic (yes, ice cover is changing so rapidly that you can even read the results in Earth’s gravitational field).

What’s exceptional about this effort is really the scale of it. Instead of just looking at changes to one area, the technique was used to chart the single largest unexplored area on our own planet. You often hear that Earth has already been extensively mapped, and certainly for inhabited areas that’s true. But for the remote regions, we’ve only begun to scratch the surface of our planet—and this map is a tantalizing clue to just what the future of earth exploration may look like.

Maps: Joshua Stevens / NASA Earth Observatory

What the Hell Caused This California Road to Suddenly Rise Up and Crumble?

Posted in GEOLOGY with tags on November 25, 2015 by 2eyeswatching

Post 4912

George Dvorsky

http://gizmodo.com/what-the-hell-caused-this-california-road-to-suddenly-r-1744393718?utm_expid=66866090-67.e9PWeE2DSnKObFD7vNEoqg.0&utm_referrer=http%3A%2F%2Fgizmodo.com%2Fwhat-the-hell-caused-this-california-road-to-suddenly-r-1744393718

What the Hell Caused This California Road to Suddenly Rise Up and Crumble?

What the Hell Caused This California Road to Suddenly Rise Up and Crumble?

A stretch of Vasquez Canyon Road in Santa Clarita has inexplicably lifted upwards over the course of just a few hours. Geologists are stumped.

As CBS Los Angeles reports, it all started last Thursday, November 19, when motorists starting calling the California Highway Patrol about the road lifting and warping. Over the course of the next three days, the road kept rising along a 200-foot (60 meter) stretch. In some places the road lifted as much as 15 feet (4.6 meters), and some sections were practically vertical.

As noted in the Santa Clarita Valley News, some people thought it was triggered by an earthquake, while others joked that it was caused by the worm-like creatures featured in the Tremors movies.

But what’s particularly strange about this event is that it wasn’t precipitated by any obvious geological phenomenon (or mythical subterranean creature, for that matter), be it an earthquake or rainstorm. Even weirder is the fact that it happened over the span of a few hours.

What the Hell Caused This California Road to Suddenly Rise Up and Crumble?

(Credit: CBS LA)

UCLA professor Jeremy Boyce recently visited the site with his students. Here’s what he told CBS News:

When we think about geology, we think about processes that happen over millions and billions of years, so the opportunity to bring students out and see something happening over a scale of hours gives them the idea that not only does geology take forever, it can also happen almost instantaneously.

Over at the AGU Landslide Blog, geologist Dave Petley makes the case that it was caused by a progressive landslide, though one without an obvious trigger. This photo, taken from the Santa Clarita Valley Signal, offers a revealing perspective:

What the Hell Caused This California Road to Suddenly Rise Up and Crumble?

(Credit: Santa Clarita Valley Signal)

Petley admits that media reports of the road rising up appear to be accurate.

A spokesperson for the LA County Department of Public Works described it as some “really extraordinary soil movement” that turned the road into “essentially catastrophic failure.” Indeed, it appears as though the soil moved underneath the road, and then lifted it up. Which is quite odd. Normally, a landslide would just wipe the road away.

Before-and-after pics of the site show that the road is situated on a box cut, and that the unloading of material from the slope likely contributed to the landslide.

What the Hell Caused This California Road to Suddenly Rise Up and Crumble?

(Credit: YouTube via AGU Landslide Blog)

Footage of the road from a few years back show signs of extensive cracking, though nothing quite on the current scale.

A geology professor at College of the Canyons referred to it as a “massive wasting event,” adding that “some sort of water event saturated the rock” causing it to act as a lubricant, thus facilitating the layers above it to move along a curved surface.

Here’s some drone footage of the site:

http://gizmodo.com/ajax/inset/iframe?id=youtube-video-Ef4e6eybLmk&start=0

Needless to say, the stretch of Vasquez Canyon Road between Lost Creek Road and Vasquez Way is closed until further notice. Geologists will continue to investigate.

[CBS News | CBS Los Angeles | AGU Landslide Blog | Santa Clarita Valley Signal]


Email the author at george@gizmodo.com and follow him at @dvorsky. Top image by KTLA5

Giant Bling: World’s Second-Largest Diamond Unearthed

Posted in GEOLOGY with tags on November 21, 2015 by 2eyeswatching

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Giant Bling: World’s Second-Largest Diamond Unearthed

Spectacular Geology: Amazing Photos of the American Southwest

Posted in GEOLOGY with tags on October 6, 2015 by 2eyeswatching

Post 4844

Spectacular Geology: Amazing Photos of the American Southwest

What Caused This Gaping Hole to Appear On an Australian Beach?

Posted in GEOLOGY with tags on October 1, 2015 by 2eyeswatching

Post 4840

George Dvorsky

http://io9.com/what-caused-this-gaping-hole-to-appear-on-an-australian-1733553802

What Caused This Gaping Hole to Appear On an Australian Beach?

What Caused This Gaping Hole to Appear On an Australian Beach?

This past weekend, a large portion of an Australian beach suddenly collapsed into the ocean. Initial reports indicated it was a sinkhole, but geologists say it’s more likely to be the result of a unique near-shore landslide.

The Inskip Sinkhole, as it was first described, appeared on Saturday September 26 at the Inskip Peninsular at MV Beagle Point, north of Rainbow Beach. Thankfully, there was no loss of life, but witnesses say a caravan, a car, and some tents were flushed into the sea. Check out some first-hand accounts of the incident here and an image gallery here.

The cavity measures about 655 feet long (200 meters), 164 feet wide (50 meters), and up to 30 feet deep (9 meters). That’s bigger than a football field. Around 300 campers were evacuated from Inskip Point after the incident. The hole now appears to be stable, but there is still concern that more trees may fall down, and that other sections of the beach may soon collapse.

What Caused This Gaping Hole to Appear On an Australian Beach?

Image credit: Leonie Mellor/ABC News

At first, experts said the phenomenon was caused by a sinkhole, which is essentially a collapsed cave. Over the last few days, however, realization has set in that the hole was probably caused by a submarine landslide, or what’s also known as a near-shore landslide. A report from the Sunshine Coast Dailyexplains:

A Queensland Parks and Wildlife spokeswoman said the event was unlikely to be related to or caused by earthquake activity.

“Rather, it’s most likely a natural phenomenon caused by the undermining of part of the shoreline by rapid tidal flow, waves and currents,” she said. “When this occurs below the waterline, the shoreline loses support and a section slides seaward, leaving a hole, the edges of which retrogress back towards the shore.’’

Peter Davies, a geologist at the University of the Sunshine Coast, added that the liquefaction visible at the site might be similar to processes seen at events triggered by earthquakes, where buildings fall into soft, loose, wet dirt that was once firm.

According to geologist Ted Griffin, a large channel between Inskip Pt and Fraser Island builds up a “shoulder” of sand, and then falls away, describing it as “a very unstable cliff of sand,” reports the Sunshine Coast Daily.

Geologist Dave Petley from the University of East Anglia in the UK says that it “would be fascinating to see some high resolution bathymetry data for this area as these slope failure events should leave a very distinctive deposit on the seabed,” adding that “the exact mechanism of failure, and its causes, are not clear to me and would be worthy of further investigation.”

Via AGU Blogosphere’s Landslide Blog!

More Big Earthquakes Coming to California, Forecast Says

Posted in GEOLOGY with tags , on September 13, 2015 by 2eyeswatching

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More Big Earthquakes Coming to California, Forecast Says

A new view of California’s earthquake risk slightly raises the likelihood of big earthquakes in the Golden State, but lowers the chance that people in some regions will feel shaking from smaller, magnitude-6.7 quakes.

The new report does not predict when or where earthquakes will strike, nor how big the next quake will be; instead, it provides a better sense of how often earthquakes will occur and how likely faults are to break in the next three decades. This information helps set earthquake insurance rates and building codes in California.

Under the new forecast, the likelihood of a magnitude-8 earthquake in the next 30 years has increased from about 4.7 percent to 7 percent. A magnitude-8 quake would be twice as strong as the devastating 1906 San Francisco earthquake, a magnitude 7.8. [Album: The Great San Francisco Earthquake]

Meanwhile, the analysis said that Californians should expect a magnitude-6.7 quake to occur every 6.3 years somewhere in the state, which is less than the estimate of every 4.8 years from the previous forecast, released in 2007.

According to the new model, magnitude-8 earthquakes are still exceedingly rare in California. An earthquake of that size would require an extraordinarily long break along the San Andreas Fault, something that may happen only every 500 years.

“The model is probably good news for a homeowner, because they are more threatened by a small, local earthquake than a big, rare, distant earthquake,” said Ned Field, lead author of the report and a U.S. Geological Survey research scientist in Golden, Colorado.

But earthquake insurance rates and building codes may change to reflect the uptick in great earthquakes, Field said. A magnitude-8 earthquake triggers long and fast shaking that is highly damaging to buildings and structures such as bridges.

One big, faulted family

The state’s magnitude-6.7 earthquake cycle slowed because scientists now calculate earthquake risk in a way that reflects how earthquakes actually happen, the report authors said. The new method takes into account that earthquakes sometimes jump across fault lines, Field said. Three of California’s recent big earthquakes crossed fault lines: the 1992 Landers quake, the 1999 Hector Mine quake and the 2010 El Mayor-Cucapah quake. The 2007 study had chopped faults into pieces that broke separately during earthquakes.

“We’ve come to realize that we’re not dealing with separate, isolated faults. We’re dealing with an interconnected fault system,” Field told Live Science.

California straddles the boundary between two tectonic plates — the North America and Pacific plates — that have been sliding past one another for 30 million years. Over the millennia, Earth’s crust has been sliced and diced into hundreds of faults, forming an interconnected system that resembles a huge, braided river. The updated model reflects this complexity, adding 150 more faults than were included in the 2007 version. Scientists knew the faults existed in 2007, but didn’t have a good idea of their potential to cause damage. GPS monitoring helped reveal how strain builds up along these newly added faults, Field said. [Image Gallery: This Millennium’s Destructive Earthquakes]

The new earthquake forecast is the culmination of a $10 million, seven-year analysis of California’s faults. It brings together everything from historical earthquake reports to precise GPS monitoring of faults into a statistical model called the “Third Uniform California Earthquake Rupture Forecast” or UCERF3. It was compiled by the U.S. Geological Survey, the Southern California Earthquake Center and the state Geological Survey, with reviews by outside experts.

The report’s 30-year period was chosen because it’s the average length of a single-family mortgage. And a magnitude-6.7 earthquake was picked because it is the size of the 1994 Northridge quake, which wreaked havoc in Los Angeles.

The chance of another Northridge-size quake somewhere in California in the next 30 years is a near certainty, at above 99 percent, according to the report, which was released Tuesday (March 11).

San Andreas is ready to rumble

Looking at individual faults, the southern San Andreas Fault near Los Angeles poses the greatest risk over the next 30 years, the researchers said. This fault, the state’s biggest, hasn’t unleashed an earthquake in this region since 1857. There is a 19 percent chance that a magnitude-6.7 quake will occur on the southern San Andreas in the next 30 years, compared to 6.4 percent for the fault’s northern stretch near San Francisco. Southern California’s overall earthquake risk for this size temblor is 93 percent in the next three decades.

“The seismic hazards are higher in Southern California than in Northern California right now,” said Tom Jordan, a report co-author and director of the Southern California Earthquake Center. “People in Southern California should realize that the next 50 years are likely to be much more seismically active. The last 50 years are not what we would consider to be normal.”

In Northern California, the Bay Area’s biggest earthquake risk comes from theHayward Fault, with a 14.3 percent risk of a magnitude-6.7 quake over the next 30 years. (A short stretch of the Hayward Fault also has a higher, 22.3 percent risk over the next 30 years.)

The new forecast is a reminder that the state’s nearly 40 million residents live inearthquake country, Field said. “People should live every day like it could be the day of the big one,” he said.

Additional resources:

U.S. Geological Survey: A fact sheet on the new earthquake forecast.

Third Uniform California Earthquake Rupture Forecast: A Google Earth file with fault probabilities and reports describing how the model was developed.

Follow Becky Oskin @beckyoskin. Follow Live Science @livescience,Facebook &Google+. Originally published on Live Science.

 

What is Plate Tectonics?

Posted in GEOLOGY with tags on September 13, 2015 by 2eyeswatching

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What is Plate Tectonics?

Tectonic plates of the Earth. 
Credit: USGS

View full size image

From the deepest ocean trench to the tallest mountain, plate tectonics explains the features and movement of Earth’s surface in the present and the past.

Plate tectonics is the theory that Earth’s outer shell is divided into several plates that glide over the mantle, the rocky inner layer above the core. The plates act like a hard and rigid shell compared to Earth’s mantle. This strong outer layer is called the lithosphere.

Developed from the 1950s through the 1970s, plate tectonics is the modern version of continental drift, a theory first proposed by scientist Alfred Wegener in 1912. Wegener didn’t have an explanation for how continents could move around the planet, but researchers do now. Plate tectonics is the unifying theory of geology, said Nicholas van der Elst, a seismologist at Columbia University’s Lamont-Doherty Earth Observatory in Palisades, New York.

“Before plate tectonics, people had to come up with explanations of the geologic features in their region that were unique to that particular region,” Van der Elst said. “Plate tectonics unified all these descriptions and said that you should be able to describe all geologic features as though driven by the relative motion of these tectonic plates.”

The driving force behind plate tectonics is convection in the mantle. Hot material near the Earth’s core rises, and colder mantle rock sinks. “It’s kind of like a pot boiling on a stove,” Van der Elst said. The convection drive plates tectonics through a combination of pushing and spreading apart at mid-ocean ridges and pulling and sinking downward at subduction zones, researchers think. Scientists continue to study and debate the mechanisms that move the plates.

Mid-ocean ridges are gaps between tectonic plates that mantle the Earth like seams on a baseball. Hot magma wells up at the ridges, forming new ocean crust and shoving the plates apart. At subduction zones, two tectonic plates meet and one slides beneath the other back into the mantle, the layer underneath the crust. The cold, sinking plate pulls the crust behind it downward.

Many spectacular volcanoes are found along subduction zones, such as the “Ring of Fire” that surrounds the Pacific Ocean.

Plate boundaries

Subduction zones, or convergent margins, are one of the three types of plate boundaries. The others are divergent and transform margins.

At a divergent margin, two plates are spreading apart, as at seafloor-spreading ridges or continental rift zones such as the East Africa Rift.

Transform margins mark slip-sliding plates, such as California’s San Andreas Fault, where the North America and Pacific plates grind past each other with a mostly horizontal motion.

Cross-section illustration of plate boundaries

This artist’s cross-section illustrates the main types of plate boundaries.
Credit: USGS/José F. Vigil from This Dynamic Planet

Reconstructing the past

While the Earth is 4.54 billion years old, because oceanic crust is constantly recycled at subduction zones, the oldest seafloor is only about 200 million years old. The oldest ocean rocks are found in the northwestern Pacific Ocean and the eastern Mediterranean Sea. Fragments of continental crust are much older, with large chunks at least 3.8 billion years found in Greenland.

With clues left behind in rocks and fossils, geoscientists can reconstruct the past history of Earth’s continents. Most researchers think modern plate tectonics began about 3 billion years ago, based on ancient magmas and minerals preserved in rocks from that period.

“We don’t really know when plate tectonics as it looks today got started, but we do know that we have continental crust that was likely scraped off a down-going slab [a tectonic plate in a subduction zone] that is 3.8 billion years old,” Van der Elst said. “We could guess that means plate tectonics was operating, but it might have looked very different from today.”

As the continents jostle around the Earth, they occasionally come together to form giant supercontinents, a single landmass. One of the earliest big supercontinents, called Rodinia, assembled about 1 billion years ago. Its breakup is linked to a global glaciation called Snowball Earth.

A more recent supercontinent called Pangaea formed about 300 million years ago. Africa, South America, North America and Europe nestled closely together, leaving a characteristic pattern of fossils and rocks for geologists to decipher once Pangaea broke apart. The puzzle pieces left behind by Pangaea, from fossils to the matching shorelines along the Atlantic Ocean, provided the first hints that the Earth’s continents move.

Follow Becky Oskin @beckyoskin. Follow LiveScience @livescience,Facebook &Google+.

 

What Is a Subduction Zone?

Posted in GEOLOGY with tags on September 13, 2015 by 2eyeswatching

Post 4801

What Is a Subduction Zone?

A subduction zone is the biggest crash scene on Earth. These boundaries mark the collision between two of the planet’s tectonic plates. The plates are pieces of crust that slowly move across the planet’s surface over millions of years.

Where two tectonic plates meet at a subduction zone, one bends and slides underneath the other, curving down into the mantle. (The mantle is the hotter layer under the crust.)

Tectonic plates can transport both continental crust and oceanic crust, or they may be made of only one kind of crust. Oceanic crust is denser than continental crust. At a subduction zone, the oceanic crust usually sinks into the mantle beneath lighter continental crust. (Sometimes, oceanic crust may grow so old and that dense that it collapses and spontaneously forms a subduction zone, scientists think.)

If the same kind of crust collides, such as continent-continent, the plates may crash together without subducting and crumple together like crashing cars. The massive Himalaya mountain chain was created this way, when India slammed into Asia.

Scientists first identified subduction zones in the 1960s, by locating earthquakes in the descending crust. Now, new instruments can precisely track the shifting tectonic plates.

“We can see very clear pictures of how the plates move, mostly due to GPS data,” said Vasily Titov, director of National Oceanic and Atmospheric Administration’s Center for Tsunami Research in Seattle, Washington.

Subduction zones occur all around the edge of the Pacific Ocean, offshore of Washington, Canada, Alaska, Russia, Japan and Indonesia. Called the “Ring of Fire,” these subduction zones are responsible for the world’s biggest earthquakes, the most terrible tsunamis and some of the worst volcanic eruptions.

Earthquakes

Shoving two massive slices of Earth’s crust together is like rubbing two pieces of sandpaper against each other. The crust sticks in some places, storing up energy that is released in earthquakes. The massive scale of subduction zones means they can cause enormous earthquakes. The largest earthquakes ever recorded were on subduction zones, such as a magnitude 9.5 in Chile in 1960 and a magnitude 9.2 in Alaska in 1964.

“Subduction zones are huge boundaries, so they generate very large earthquakes,” Titov told Live Science.

Why are subduction zone earthquakes the biggest in the world? The main reason is size. The size of an earthquake is related to the size of the fault that causes it, and subduction zone faults are the longest and widest in the world. The Cascadia subduction zone offshore of Washington is about 620 miles (1,000 kilometers) long and about 62 miles (100 km) wide.

Smaller earthquakes also strike all along the descending plate, also called a slab. Seismic waves from these temblors and tremors help scientists “see” inside the Earth, similar to a medical CT scan. The quakes reveal that the sinking slab tends to bend at an angle between 25 to 45 degrees from Earth’s surface, though some are flatter or steeper than this.

Sometimes, the slabs may tear, like a gash in wrinkled paper. Pieces of the sinking plate can also break off and fall into the mantle, or get stuck and founder.

Washington and Oregon subduction zone

A 3D model of a subduction zone off the coast of Washington and Oregon.
Credit: USGS.

Tsunamis

Subduction zones are usually along coastlines, so tsunamis will always be generated close to where people live, Titov said. “There’s a silver lining there,” he said. “If these earthquakes happened underneath a city, the city would have no chance. But the bad news is sometime a tsunami is generated.”

When subduction zone earthquakes hit, Earth’s crust flexes and snaps like a freed spring. For earthquakes larger than a magnitude 7.5, this can cause a tsunami, a giant sea wave, by suddenly moving the seafloor. However, not all subduction zone earthquakes will cause tsunamis. Also, some earthquakes trigger tsunamis by sparking underwater landslides.

Whatever their cause, the tsunami threat from subduction zones is monitored by government agencies such as NOAA in countries around the Pacific Ocean. Tsunamis may strike in minutes for coastal areas near an earthquake, or hours later, after the waves travel across the sea.

Volcanoes

As a tectonic plate slides into the mantle, the hotter layer beneath Earth’s crust, the heating releases fluids trapped in the plate. These fluids, such as seawater and carbon dioxide, rise into the upper plate and can partially melt the overlying crust, forming magma. And magma (molten rock) often means volcanoes.

Looking at the Pacific Ring of Fire reveals the link between subduction zones and volcanoes. Inland of each subduction zone is a chain of spouting volcanoes called a volcanic arc, such as Alaska’s Aleutian Islands. The Toba volcanic eruption in Indonesia, the largest volcanic eruption in the past 25 million years, was from a subduction zone volcano.

Email Becky Oskin or follow her @beckyoskin. Follow us @livescience,Facebook &Google+.

Additional resources