The Earth Story

INSAR

Radar is an extremely useful tool for monitoring changes in the Earth’s surface. Interferometric synthetic aperture radar, or INSAR, can accurately measure tiny changes in the Earth’s surface.

Radar waves pass through Earth’s atmosphere and will bounce off land surfaces. Radar is a form of light - electromagnetic radiation - so like light it is a type of wave with a frequency/wavelength. When radar bounces from the surface to a spacecraft, it arrives back at a specific point in each wave. It's difficult to turn small changes in wavelength from pixel to pixel into any useful information since they’re a function of many properties of the surface, but if 2 images taken close together in time are subtracted from each other, tiny changes from one frame to another stand out. Those tiny changes in the wavelength of the returning energy are reflected in changes in the colors on an INSAR interferogram like this one. As the wavelength of the returning energy changes, it either builds constructively on the waves in the previous pass or interferes destructively.

INSAR is a tool that can show changes in the Earth’s surface from one scene to the next – changes like deformation in a volcano or motion from an earthquake. If 2 closely timed radar images are available, earthquake motions can be understood and volcanic eruption warnings can be given, but doing so requires a satellite built to do the measurement.

Previous satellites could do these measurements, but they weren’t built to do rapid overpasses. A few years ago, the European Space Agency launched its Sentinel-1A satellite (http://on.fb.me/1B1f6Jj), the first in its next-generation series of Earth-observing spacecraft. That satellite carries radar specifically designed for INSAR – it will be able to image every point on Earth’s surface every 12 days.

This INSAR image shows ground deformation in an earthquake in Oaxaca , Mexico last year. The ground moved by a maximum  of about 40 centimeters in this earthquake, so each of the contours of color represents about 3 centimeters of ground motion. The points marked show estimates of the earthquake epicenter based on seismic measurements made by the USGS and Mexican seismic networks; clearly based on this image, the nearby seismic instruments from the Mexican seismic network produced a more precise estimate of the epicenter location.

-JBB

Image credit: EOS/ESA/NASA https://disasters.nasa.gov/oaxaca-mexico-earthquake-2018/insar-map-deformation-due-m72-oaxaca-earthquake https://eos.org/project-updates/earthquake-monitoring-gets-boost-new-satellite

Collapsing ice cap

This cracked-up glacier is one of the outlets of Kapp Mohn outlet glacier that drains the Austfonna ice cap in the Svalbard archipelago, a small group of islands found north of Norway in the Arctic Ocean.

Austfonna is a large, permanent ice cap, sitting in the high ground on a portion of Nordaustlandet Island. It covers an area of 8,200 square kilometers and the ice is on average over 500 meters thick. Or at least, it used to be.

This ice cap is literally collapsing before our eyes. The outlet glacier pictured in this image accelerated by a factor of 25 from 2013 to 2016, causing dramatic drops in the thickness of the ice upstream. The European Space Agency has launched several satellites in their Sentinel program containing sophisticated radar systems able to measure small changes in elevation on the Earth’s surface, including the elevation of ice caps. Combined with previous measurements of the thickness of this ice cap, scientists from the University of Leeds determined that since 2012, this ice cap has lost 1/6 of its thickness, driven by the acceleration at this outlet glacier.

The waters of the Arctic Ocean have warmed at a rapid pace relative to the rest of the world over recent years, and 2012 in particular was a year of exceptional melting and warmth in the arctic due to some extreme storms. The sudden movement in this glacier suggests that this pulse of heat has helped destabilize glaciers in the surrounding territory and it is happening at an exceptionally rapid pace. Several other glaciers in this area have begun similar surges over the past few years - accelerating their motion towards the ocean by a factor of 10 or more. 

At present, about 1/3 of the sea level rise in the last century is estimated to have been contributed by melting glaciers, but sudden acceleration in large ice caps like this one keep making the case that the ice caps worldwide, which hold large quantities of water on land, are one way that sea level rise can and will accelerate as the planet warms due to human-imposed increases in greenhouse gases. 

-JBB

Image credit: Thorben Dunse, University of Oslo http://wapo.st/1zH9rs0

Read more: http://dx.doi.org/10.1002/2014GL062255 http://www.sciencedaily.com/releases/2015/01/150123081723.htm http://www.cpom.org/research/largeice.htm https://www.smithsonianmag.com/science-nature/what-surging-glaciers-svalbard-tell-us-about-future-rising-seas-180970060/ https://www.the-cryosphere-discuss.net/tc-2017-5/tc-2017-5.pdf

HOW DO YOU KNOW – if a volcano is going to erupt?

Predicting volcanic eruptions has long been considered about as probable as predicting, say, earthquakes. The possibility of using acutely sensitive satellite radar imaging data now shows promise in the prediction and monitoring of potential volcanic events.

Eruptions require that magma moves upward from a deeper source: the overfill of a magma chamber can cause doming of the Earth’s crust above it. Observation of the uplift accompanying this could be used to predict an eruption. The swelling of the 40km x 60km Yellowstone Supervolcano caldera has been observed over the last decade, but just what this means for future eruptions is not yet clear.

To date, most studies of surface uplift in volcanic centers have been dominated by ground-based observation (using GPS and other sensitive topographic measurements); a great many potentially active volcanoes are inaccessible to study, “off the radar,” so to speak, of ground-based observation. Ground based research is, in some ways, simply too close to the volcanic subject – it is comparable to the examination of a single tree to predict the growth of a forest.

A recent study lead by Dr Juliet Biggs of Bristol University has evaluated systematic satellite imagery, some reaching back 18 years, that includes the host regions of 500 volcanoes. Among these are volcanic centers where, essentially, no geoscientist has yet to tread. The remote sensing images prove to be acutely sensitive for monitoring topographic change. This immense storehouse of data was evaluated statistically, demonstrating, in short: 94% of volcanic centers that did not show caldera uplift did not erupt; 46% of those that did show deformation, did erupt.

Applying this simple probability forecast to Yellowstone would imply a near 50% chance of eruption. However, the study points out that some volcanoes may show uplift over a period of just days, and others over centuries. More systematic monitoring is needed.

What this study does do is establish that remote satellite imaging is a feasible research pathway that could lead to prediction of volcanic episodes. The cost of the study (http://comet.nerc.ac.uk/) that includes this research (other studies in this endeavor include earthquake prediction studies!) is ~$4.7M; a typical satellite may cost ~$300M; the economic cost of the 1991 Mount Pinaturbo alone was ~$1.5 billion, in addition to the inestimable deaths of 800 people. This is cost-efficient research at its best!

I highly recommend watching the short video that illustrates the research methodology, and also is the source of the image and digest of research for this post, at: http://www.bristol.ac.uk/news/2014/april/volcano-deformation.html?utm_source=twitterfeed

Annie R

More sources relevant to this post: 'Global link between deformation and volcanic eruption quantified by satellite imagery' by J. Biggs, S.K. Ebmeier, W.P, Aspinall, Z. Lu, M.E. Pritchard, R.S.J. Sparks, T.A. Mather in http://www.nature.com/ncomms/index.html Other sources: Yellowstone Caldera uplift: http://tinyurl.com/pbaxbgj http://geography.about.com/od/globalproblemsandissues/a/pinatubo.htm

Let’s look at Venus – REALLY Close!

The Bayou Corne sinkhole

This image shows a man-made disaster in the state of Louisiana known as the Bayou Corne sinkhole. The sinkhole formed when the surface collapsed on August 3rd, 2012 following a series of small earthquakes, and rapidly filled in with groundwater.

This sinkhole is the subject of new research published in the journal “Geology” that describes interesting processes occurring before the sinkhole opened that could have implications for future sinkholes.

The sinkhole is located on top of a mine which was extracting salt from the underlying Napoleonville salt dome by pumping water in, dissolving the salt, and pumping out the brine. This process formed a large gap in the salt dome which collapsed, forming a mile-deep cave and releasing a variety of gases including methane and hydrogen sulfide from a nearby natural oil reservoir into the air. Several hundred local residents were evacuated, Louisiana declared a state of emergency, and to this day most of the residents have been unable to return to their homes.

Residents of the area were complaining of ground motions in the months before the collapse. Using satellite data including images and radar, scientists at the Jet Propulsion laboratory and US Geological survey have reconstructed parts of what happened before the collapse.

No deformation was seen prior to June of 2011, but for about a year beforehand, the ground started subtly shifting. In total, 26 centimeters of sideways motion were detected right above the location where the sinkhole formed in the year prior to collapse. The ground itself creaked and slid as the support underneath weakened.

The earthquake swarm started in June of 2012, slightly after ground motion began. Thus, this sinkhole gave a long warning period before it formed. If this technique can be generalized, similar ground motions might give a warning before large sinkholes form in other populated areas.

A variety of lawsuits are pending against the companies that operated the mines. The sinkhole continues growing today, and is now threatening nearby highway 70.

-JBB

Image credit: http://www.flickr.com/photos/assumptionoep/7832115946

AGU abstract: http://www.sciencecodex.com/new_geology_research_explores_intriguing_questions-125145 http://m.livescience.com/42103-radar-catches-bayou-corne-sinkhole-form.html?cmpid=514645

Snow in the desert The Sahara is not renowned for precipitation, so when snow fell near the Algerian town of Ain Sefra where the desert meets the Atlas mountains (normally one of the globe's warmest places) some days ago it provoked a flurry of attention and brought us these lovely satellite photos (with the NASA one being a LANDSAT image draped over a radar based elevation model originally takenby the space shuttle). The fall amounted to between 10 and 30 cm at altitudes above 1000 metres and it lasted just long enough for some locals to enjoy sliding down dunes on improvised sledges. It was the third recorded fall in the last 37 years. Loz Image credit: 1: NASA 2: Copernicus Sentinel/ESA https://go.nasa.gov/2rlRJ0t http://bit.ly/2Beu2GY

Original video caption:

The incredible shrinking Denali!

This week, Denali, the tallest peak in the United States, officially shrank by 26 meters (83 feet), from 6,194 meters to 6,168 meters above sea level.

Of course, the mountain itself didn’t change, only our measurements of it. Denali’s elevation was originally measured to be 20,320 feet in 1952 based on its properties in photographs. A 1989 field survey measured it to be 20,306 feet in height, but in many cases (including state documents) the 1952 estimate still seems to have been used. In those units, the officially acknowledged height now is 20,237 feet.

In much of the United States, the most current topographic maps date back to the 1960’s and 1970’s, well before digital maps and satellite technologies became available. Some areas have been updated via satellites but the official topographic maps used by most government offices are the older ones, done with the best surveying technologies available at the time.

So no, Denali isn’t really shrinking (just in case anyone is wondering, if it really shrank by 20+ meters over 25 years, that would put it on pace to vanish in less than 10,000 years, so no, it is not eroding or changing that quickly), our maps are just getting better. And just to note, it remains the tallest peak in North America.

Starting in 2010, a partnership between the US Federal Government and Alaskan state government has been re-mapping Alaska with modern techniques including radar measurements; that mapping project produced this new height. Other new details have come out as well; an entire ridgeline of another mountain in Denali National Park, Mt. Dickey, was completely missing from the topographic maps and has now appeared.

The goal is to finish the Alaskan project by 2016, but Alaska isn’t the only place that needs this treatment. Much of the U.S. needs re-mapped using modern techniques, and it’s not just for reasons of curiosity. Building permits, flood insurance, and geologic risk assessments for property and development benefit hugely from accurate maps, and the more accurate they are the more money is saved in the end.

-JBB

Image credit: Wikimedia Commons http://commons.wikimedia.org/wiki/File:Wonder_Lake,_Denali.jpg

Press report: http://ltgov.alaska.gov/treadwell/press-room/full-press-release.html?pr=215

Previous coverage of updating of maps: https://www.facebook.com/TheEarthStory/posts/531217026939346

Why do storms break up and go around (name your town here)?

If you’ve ever watched a line of storms moving into your area on the radar, you may have asked this question yourself. A line of storms may appear solid and menacing at a distance, and then as the storms get closer, gaps appear in the line, and your house may get missed by the rain. After the storms pass, the gaps disappear, and you see a solid line of storms again. The storms are not actually breaking up and reforming around your town. What you are seeing is a result of the changing size of the radar beam as it moves away from the radar. At close range, the beam is narrower and can see finer details, such as gaps in the storms. At a distance, the radar beam is much wider and cannot see the gaps between storms, so a line of storms at a distance appears to be solid, when it is really not.

Think of the radar beam as a beam of light from a flashlight. If you hold a flashlight close to a wall in a dark room, you will see a small beam of light. As you back away from the wall, the beam of light gets larger. The energy coming from the radar works in much the same way. Near the radar, the beam of energy is much narrower, but as the beam moves out away from the radar, it grows in size, much like a flashlight beam.

The spreading radar beam affects the resolution of the image. Small features can be seen close to the location of the radar, but they are often obscured at a greater distance. So, at a distance from the radar, a line of storms may appear solid, because the beam is too wide to resolve the gaps between storms. As the storms get closer to the radar, the narrower beam can “see” the gaps.

Also, the life cycle of a typical thunderstorm is only around 30 minutes to 1 hour. Storms are changing and evolving all the time. A storm at a distance that is an hour away will change considerably by the time it reaches your location. It may weaken and die out before it ever reaches you, or it may change the direction it is moving and miss your location completely.

Here’s just one more thing to keep in mind. Due to the curvature of the earth, the radar beam gets higher in the sky as it moves away from the radar. The radar beam is sampling the upper levels of storms at a distance, and looking at the lower levels of storms close to the radar. This can also affect what you are seeing on the radar screen.

-Amy

For more on how radars work, visit the JetStream mini-course on radars:

http://oceanservice.noaa.gov/education/yos/resource/JetStream/doppler/doppler_intro.htm

Photo credit NOAA/NWS

NASA discovers “Grand Canyon of Greenland”

Since 2009, NASA has undertaken a project known as “Operation Icebridge”, a campaign of flights to monitor and characterize the Earth’s ice sheets. It uses specialized equipment, such as ice-penetrating radar, to measure the thickness and monitor the movement of glaciers in Greenland and Antarctica. Using data from Icebridge, a team from the University of Bristol have made a startling discovery. Buried beneath the icecap at the northern end of Greenland there sits a canyon, the canyon you see illustrated here (image is looking towards the north).

This canyon is of staggering scale. It is up to half the depth of the Grand Canyon in Arizona with depths of 800 meters at its deepest segments. The canyon is 750 kilometers long, longer than the Grand Canyon, and up to 10 kilometers wide.

The mega-canyon drains to the north and almost certainly pre-dates the icesheets and was carved by water in a period when the planet was warmer. The dimensions of the canyon are consistent with large canyons carved by water, and it meanders through the terrain as water-carved canyons do. This canyon was carved over millions of years by water draining from the center of Greenland to the north prior to its trapping under the ice sheets.

Today this canyon likely serves as a major conduit for flow of water along the base of the glaciers in Greenland, allowing melt water to flow from the center of the icecap out to sea. Therefore, this canyon and the hydrology surrounding it will likely be the focus of intensive study in the future to determine its impact on the stability of the Greenland ice sheet and the role it will play in allowing warmer waters to interact with the core of the ice sheet.

-JBB

Image credit: NASA, go here for a fly-through video http://www.nasa.gov/content/goddard/nasa-data-reveals-mega-canyon-under-greenland-ice/

Original paper (Subscription): http://www.sciencemag.org/content/341/6149/997.full_ _

Mt. St. Helens with its blown-out north rim, scanned by Radar from the space shuttle (SRTM) then carved by machine from eucalyptus wood.

Faulting in Amatrice Quake

Last summer and fall, a series of major earthquakes struck the center of the Italian Peninsula, heavily damaging a number of communities. The first of these quakes struck on August 24 near the city of Amatrice; these images show some of the first published science resulting from that earthquake and a new understanding of the fault that generated them.

When the earthquake happened, it immediately generated signals that were detected by seismic monitoring stations around the world. This data, when paired with enough computing power, can be used to constrain the exact location where the earthquake started in the ground (called the hypocenter – the epicenter of a quake is the point on the planet’s surface directly above the hypocenter). Within days after the quake, satellites including the European Space Agency’s Sentinel-1A satellite had traveled over the area and taken radar maps of the ground, giving precise measurements of the deformation of the land surface. Combining these two data sets, scientists could begin to understand how the fault ruptured at depth and what that rupture did to the surface.

According to the radar data, two different sections of the surface ruptured in the quake with a gap between them. These two sections are shown on the slopes of mount Vettoretto in the frame on the right of this photo and are named the northern Gorzano and Redentore-Vettoretto faults. The Northern Gorzano fault moved about 80 cm during the quake and the Redentore-Vettoretto moved 90 cm.

That two separate faults with no linkage between them moved in the same quake illustrates the complexity of the geologic structure in this part of Italy. To better understand the fault structure in Italy, the scientists used complicated computer coding to simulate the area beneath the faults and how, as fault motion continued underground, it would produce all of the deformation measured on the surface.

As you see in the 3-D model image, the best fit to explain all the motion during this earthquake is to have both of these faults slope down to the west and eventually, at about 8 kilometers depth, join together. Based on the seismic data, this is a particularly interesting location as the hypocenter of the quake is at basically this exact same depth and located right where the two faults are projected to join together into a single fault.

In other words, the point where the two shallow faults are split apart was the point where the rocks actually began to fail. That spot was a point of extra stress and when that point ruptured, the breakage spread out and moved upwards along both of the faults, eventually reaching the surface on both of them (marked as cosesismic fractures on the image). The complex structure of these faults coming together at depth generated a zone of extra stress right where they joined and that zone was key to the complex, multiple-fault rupture seen in this quake.

Several other quakes since then, including others in Italy and later in the year the large quake in New Zealand, have seen similar patterns of multiple fault ruptures. Similar satellite data will be available for all of them – this was the first paper published using this type of modeling for Italy and there will presumably be others later on since there were quakes after this one. This work will help scientists better understand the stresses that trigger complicated, multi-fault earthquakes and therefore will help us better assess the associated hazards for future quakes.

-JBB

Image credit and original paper (Open access): http://onlinelibrary.wiley.com/doi/10.1002/2016GL071723/full

H.A.A.R.P SHUT DOWN

The High Frequency Active Auroral Research Program (HAARP), located in Gakona, Alaska, has closed down. The facility has been shuttered since early 2013, and the site is currently abandoned. HAARP’s manager, Dr James Keeney at Kirtland Air Force Base in New Mexico, said the closure effectively comes down to money. No one is currently on site, access roads are blocked, buildings are chained and the power turned off; HAARP’s website through the University of Alaska no longer is available.

The goal of HAARP was to study the properties and behaviour of Earth's ionosphere, which is part of the upper atmosphere and lies at about 85 km (53 mi) to 600 km (370 mi) altitude. The HAARP programme began in 1990 and the major construction at the facility was completed in 2007. HAARP was used to study the natural processes in the ionosphere that occur under the natural, yet stronger, influence of solar interaction. This also includes studying how the ionosphere affects radio signals. The facility was sited in Alaska as it is the only US state in the auroral region and its ionosphere has a variety of conditions that HAARP can study. HAARP itself consists of 180 antennas within a land area of about 14 hectares (35 acres). The array and its integrated transmitters have a total radiated power capability of about 3,600 kilowatts.

The Defense Advanced Research Projects Agency (DARPA) is expected on the HAARP site as a client to finish up some research later this year. DARPA has nearly $8.8 million in its FY 14 budget to research “physical aspects of natural phenomena such as magnetospheric sub-storms, fire, lightning and geo-physical phenomena.”

HAARP gave notice two years ago that it would be shutting down and therefore did not submit a budget request for FY 15. According to Keeney, the diesel generators on site no longer pass the Clean Air Act, and repairing them to meet EPA standards will cost $800,000. Running the facility costs $300,000 a month and to run it at full capacity for 10 days costs $500,000.

The HAARP facility has been integral to many different research projects and so many will keenly miss its closure. In 1997, HAARP transmitted test signals on HF (3.4 MHz and 6.99 MHz) and solicited reports from hams and short-wave listeners in the “Lower 48” to determine how well the HAARP transmissions could be heard to the south. In 2007, Radar pulses from the HAARP research station were bounced off the Moon and picked up by a radio telescope system. This was the lowest frequency radar echo from the Moon ever detected on Earth; it took 2.4 seconds to radio the Moon. Scientists analysing the echo gained insights into the properties of the lunar sub-surface topography (http://on.fb.me/196ueru). More recently, HAARP scientists successfully produced a sustained high-density plasma cloud in Earth’s upper atmosphere (http://on.fb.me/15364Kp). HAARP research is published in a number of journals, including the Journal of Geophysical Research, Geophysical Research Letters, and Radio Science. Some are available here: http://bit.ly/13RZA3Z

Though the Air Force has possession of the facility for now, if no other agencies step forward to take it over, HAARP will be dismantled.

-TEL

Previous posts on HAARP research: http://on.fb.me/196ueru, http://on.fb.me/15364Kp

http://www.arrl.org/news/view/haarp-facility-shuts-down Image: an aerial view of the HAARP facility, copyright ARRL

Frosty the Volcano

Frosty the volcano was a chilly, remote cone. Possibly jolly and happy, can’t tell because I’ve never been. It is the highest peak in this small area found at the far tip of the Alaska Peninsula, the last major volcano on the Peninsula before it separates into the Aleutian Islands. It has no major recent eruptions, although it is though to have had at least 2 caldera forming eruptions during the Holocene based on geologic mapping evidence. The peak is the youngest and highest of the larger Cold Bay volcanic field, which produced the surrounding smaller peaks. The peak reaches 1920 meters above sea level.

This gif was created using SRTM data; radar data characterizing the Earth’s Surface obtained from the space shuttle. Modern satellites regularly map across the planet using radar and can make accurate maps of how these structures deform when magma begins moving deep underneath them – an important use of space-based platforms for characterizing geologic hazards on Earth.

-JBB

Gif credit: http://bit.ly/2gnkrDq References: http://bit.ly/2hba3lY http://volcano.oregonstate.edu/frosty-peak https://www.avo.alaska.edu/volcanoes/volcinfo.php?volcname=Frosty