Landslides in China!
This link takes you to a post on The Landslide Blog, showing videos of three landslides in China. The first is especially fascinating to watch.
Tag: geology
Dormant volcano near Rome reawakens
A volcano near Rome that last erupted 36,000 years ago is now showing signs of re-awakening.
Scientists previously assumed Colli Albani, a 15-kilometer (9-mile) semicircle of hills outside Rome, was an extinct volcano since there was no record of it having erupted in human history. But in recent years, scientists have observed new steam vents, earthquakes and a rise in ground level in the hills and surrounding area. These observations, along with new evidence of past eruptions and satellite data, indicate Colli Albani is starting a new eruptive cycle and could potentially erupt in 1,000 years from now, according to a new study published in Geophysical Research Letters, a journal of the American Geophysical Union.
Weird dunes on Mars
Cool image time! The image on the right, cropped and reduced in resolution to fit here, shows an area of inexplicable dark dunes located in Mars’ high northern latitudes. Located in a circular depression (whose outline can be seen across the top and left side of the image), geologists only partly understand the processes producing these dunes. As the noted on the release webpage:
However, a circular depression (probably an old and infilled impact crater) has limited the amount of sand available for dune formation and influenced local winds. As a result, the dunes here form distinct dots and dashes. The “dashes” are linear dunes formed by bi-directional winds, which are not traveling parallel to the dune. Instead, the combined effect of winds from two directions at right angles to the dunes, funnels material into a linear shape. The smaller “dots” (called “barchanoid dunes”) occur where there is some interruption to the process forming those linear dunes. This process is not well understood at present and is one motivation for HiRISE to image this area.
Be sure to look at the full image, as it covers a wider area and shows dunes that travel in all directions, forming mazelike patterns that no theory presently explains.
Geologists discover giant field of underground helium in Tanzania
Geologists have discovered a gigantic new field of underground helium gas, located in Tanzania’s Rift Valley.
Researchers figure there’s about 54 billion cubic feet of helium in just one section of the valley. To put that in context, the Federal Helium Reserve in Texas, which supplies more than 40% of domestic helium needs and contains about 30% of the world’s total helium supply, right now holds about 24.2 billion cubic feet, per Live Science.
The discovery is also important in that it wasn’t an accident. The geologists located the helium based on their theories of where they should find it.
More weird Pluto geology
Cool image time! The New Horizons science team has released an image taken during the spacecraft’s fly-by of Pluto in July 2015 showing what they are calling “fretted terrain”.
The image above is a cropped reduced section of that image. It shows the strange transition zone between the higher elevation bright areas and the lower dark plains. As they note,
New Horizons scientists haven’t seen this type of terrain anywhere else on Pluto; in fact, it’s rare terrain across the solar system – the only other well-known example of such being Noctis Labyrinthus on Mars. The distinct interconnected valley network was likely formed by extensional fracturing of Pluto’s surface. The valleys separating the blocks may then have been widened by movement of nitrogen ice glaciers, or flowing liquids, or possibly by ice sublimation at the block margins.
In other words, they really don’t know what is going on.
Mars’s giant tsunamis
New research using data from a variety of Mars orbiters suggests that large tsunamis previously smashed against the shores of the red planet, shaping the geography.
The group zeroed in on a region on Mars where the highlands known as Arabia Terra bump up against the lowlands of Chryse Planitia — a place where the waters of an ancient ocean might have lapped at the shoreline. Using imagery from several Mars-orbiting spacecraft, Rodriguez’s group identified two particular geological formations that they say formed during two different tsunamis. The first, older formation looks as if an enormous wave had rushed up onto the edge of the highlands, dropping boulders as big as 10 metres across. The water then drained back down into the ocean, leaving channels cut through the freshly deposited debris.
Then, millions of years passed. Temperatures dropped and glaciers crept across the landscape, scouring deep valleys. Finally, a second impact-generated tsunami came rushing again towards the shore. “But this time it is different,” Rodriguez says. Because the climate was so much colder, the tsunami moved over the landscape like an icy slurry. It froze before it had a chance to wash back into the ocean, leaving dense lobes of frozen debris on the ground.
They propose the waves were caused by large meteorite impacts. They also admit that there are large uncertainties in their theory and conclusions.
Increased earthquake activity at Mount St. Helens
Though the increase is not large enough to indicate the likelihood of another eruption, scientists have noted that for the past eight weeks the earthquake rates under Mount St. Helens has been increasing.
Over the last 8 weeks, there have been over 130 earthquakes formally located by the Pacific Northwest Seismic Network and many more earthquakes too small to be located. The earthquakes have low magnitudes of 0.5 or less; the largest a magnitude 1.3. Earthquake rates have been steadily increasing since March, reaching nearly 40 located earthquakes per week. These earthquakes are too small to be felt at the surface.
Once again, these quakes do yet not signal another eruption. They are more likely signs of the mountain’s continuing but long and slow adjustment back to silence after the 1980 eruption. Nonetheless, they bear watching, as a volcano will do what a volcano wants to do.
Ice and volcanoes on ancient Mars?
New data of past volcanic activity on Mars suggest that the red planet was once covered by at least one extensive ice sheet.
There is a great deal of uncertainty in this conclusion, however. They have found one example with the right geology to suggest past ice sheets under which volcanoes erupted. Translating this into an extensive ice sheet requires many assumptions that might not prove true with further research.
Halo craters on Pluto
More images from New Horizons reveal even more strange terrain on Pluto.
Data suggest that the bright rims are made of methane ice, while the dark crater floors are made of water ice, though why this has happened is a complete mystery. As they note at the link above, “Exactly why the bright methane ice settles on these crater rims and walls is a mystery; also puzzling is why this same effect doesn’t occur broadly across Pluto.”
Evidence of water on Ceres?
New data from Dawn suggests that there is significant water locked in surface of Ceres’s north polar regions.
These data reflect the concentration of hydrogen in the upper yard (or meter) of regolith, the loose surface material on Ceres. The color information is based on the number of neutrons detected per second by GRaND. Counts decrease with increasing hydrogen concentration. The color scale of the map is from blue (lowest neutron count) to red (highest neutron count). Lower neutron counts near the pole suggest the presence of water ice within about a yard (meter) of the surface at high latitudes.
Note that the data has not detected water. The blue areas on the image to the right suggest an increased amount of hydrogen, which could only be held to the surface if it was locked in some molecule, with water being the most likely candidate. Like the Moon, until we actual capture some samples, it will be difficult to confirm with certainty the presence of water.
Vast Martian dune fields
Cool image time! In the past few days the Themis camera on Mars Odyssey has taken two pictures of the vast Olympia Undae dune field near Mars’s north pole. The image to the right is only a cropped, lower resolution section of one of those images.
The image was taken during the summer, so most of the winter CO2 frost has sublimated away. Unfortunately, the website does not provide a scale, though they say the full images each cover about 12 by 43 miles of territory. Yet, both images capture only very tiny portions of the dune field, which apparently goes on and on for many hundreds of miles in all directions, looking exactly the same wherever you look.
Just imagine trying to travel though this area. It is the epitome of a trackless waste. And without some form of GPS system getting lost forever would be incredibly easy.
Titan’s tallest mountains
After more than a hundred flybys by Cassini of Titan scientists think they have located most of Titan’s mountains, including what they think will be its highest peak.
New close-up of Occator Crater’s spots
The Dawn science team have released new images taken from the spacecraft’s low orbit observations, including a close-up of the central white spot at Occator Crater, the brightest spot on Ceres.
The image on the right is a cropped though full resolution version of the full image. I have reduced it only slightly. As they note,
Occator Crater, measuring 57 miles (92 kilometers) across and 2.5 miles (4 kilometers) deep, contains the brightest area on Ceres, the dwarf planet that Dawn has explored since early 2015. The latest images, taken from 240 miles (385 kilometers) above the surface of Ceres, reveal a dome in a smooth-walled pit in the bright center of the crater. Numerous linear features and fractures crisscross the top and flanks of this dome. Prominent fractures also surround the dome and run through smaller, bright regions found within the crater.
A new gravity map of Mars
Using data from three orbiting NASA spacecraft scientists have created a new gravity map of Mars, showing the subtle variations in its gravitational field due to density differences within the planet.
The improved resolution of the new gravity map suggests a new explanation for how some features formed across the boundary that divides the relatively smooth northern lowlands from heavily cratered southern highlands. Also, the team confirmed that Mars has a liquid outer core of molten rock by analyzing tides in the Martian crust and mantle caused by the gravitational pull of the sun and the two moons of Mars. Finally, by observing how Mars’ gravity changed over 11 years – the period of an entire cycle of solar activity — the team inferred the massive amount of carbon dioxide that freezes out of the atmosphere onto a Martian polar ice cap when it experiences winter. They also observed how that mass moves between the south pole and the north pole with the change of season in each hemisphere.
Mars’ giant volcanoes shifted planet’s axis
New computer models based on the geological data from Mars suggests that when the giant volcanoes spewed their lava out they upset the planet’s equilibrium, causing the axis to tilt 20 to 25 degrees.
Not surprisingly, there remain many uncertainties with this analysis.
The first geology map of Pluto
The New Horizons science team has now released the first geology map of a portion of Pluto, seen by the spacecraft during its fly-by last year.
It is definitely worth your while to take a look at the full image, along with the legend explaining the different surface features. Most of the geological terms are merely descriptive, but the careful breakdown still provides a much deeper understanding of what is there.
A river on Mars
Cool image time! The science team for the high resolution camera on Mars Reconnaissance Orbiter this week released it monthly set of cool images. One of those images, which I have cropped and reduced to show it here, is of an ancient river on Mars, the formation process of which geologists still debate. As the scientists note,
The channel pattern, called “dendritic” because of its tree–like branching, begins at the top of the image and runs down over the rim of an ancient impact basin across the basin floor. The soil surface overlying these channels, and indeed the entire landscape, has been changed and reworked over the intervening millions of years, by the combined actions of wind and ice. Over time, the original channels become muted or even erased.
One thing I learned in writing an article for Astronomy about the rivers seen on Saturn’s moon Titan is that without plant life there is no known natural process to hold river banks in place. Instead, if the grade is shallow and not confined by bedrock cliffs, rivers will meander about randomly forming braided channels as there will be nothing on shore to hold the water within the same course. For example, on a lifeless Earth the water draining the central basin of the midwest United States would have flowed south across a wide scattered area covering the entire plains, rather than flowing within the courses of the Missouri and Mississippi rivers.
Thus, it is not surprising that this river on Mars appears muted or partly erased. It probably was never very clearly delineated in the first place.
Water unneeded to produce wet gullies on Mars
The uncertainty of science: New modeling suggests that the wet gullies seen on Mars can be produced by dry ice, not water.
The theory is not completely new, but Cedric Pilorget and François Forget, with the University of Paris-Sud, and Paris’ Pierre and Marie Curie University, respectively, flesh out the idea with some hard numbers. Their new computer model calculates seasonal changes and impacts of an underlying layer of regolith, a carbon dioxide ice layer and the carbon dioxide-dominated gas atmosphere above. The simulation can take into account a variety of latitudes, slopes and other parameters.
The scientists found that most of the gullies could be created in a process that does not require any liquid water.
A movie of Ceres
Cool movie time! The Dawn science team has released a movie compiled from images taken by the spacecraft, showing in false color the entire dwarf planet’s rotation as well as doing a fly-over of Occator Crater with its double bright spot.
I have posted the movie below the fold. The false colors illustrate the different materials so far detected on the surface, and help explain the nature and origin of the surface features.
» Read more
Bright spots on Ceres likely salt deposits
Based on an analysis of Dawn images scientists now believe that the bright spots on Ceres are salt deposits, not water ice.
Le Corre and colleagues, using images from Dawn’s framing camera, suggest that these salt-rich areas were left behind when water-ice sublimated in the past. Impacts from asteroids would have unearthed the mixture of ice and salt. “The location of some bright spots also coincide with places where water vapor was detected by other spacecraft,” said Reddy, a PSI Research Scientist. “This gives us confidence that the bright spots are likely salt deposits left over by sublimating salty water.”
While the bright spots themselves are not ice, they are what is left over after salty water evaporates.