volcanic deposits

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RESEARCH SHOWS HOW A YOUNG-LOOKING LUNAR VOLCANO HIDES ITS TRUE AGE

While orbiting the Moon in 1971, the crew of Apollo 15 photographed a strange geological feature – a bumpy, D-shaped depression about two miles long and a mile wide – that has fascinated planetary scientists ever since. Some have suggested that the feature, known as Ina, is evidence of a volcanic eruption Moon within the past 100 million years – a billion years or so after most volcanic activity on the Moon is thought to have ceased.

But new research led by Brown University geologists suggests that Ina is not so young after all. The analysis, published in the journal Geology, concludes that the feature was actually formed by an eruption around 3.5 billion years ago, around the same age as the dark volcanic deposits we see on the Moon’s nearside. It’s the peculiar type of lava that erupted from Ina that helps hide its age, the researchers say.

“As interesting as it would be for Ina to have formed in the recent geologic past, we just don’t think that’s the case,” said Jim Head, co-author of the paper and professor in Brown’s Department of Earth, Environmental and Planetary Sciences. “The model we’ve developed for Ina’s formation puts it firmly within the period of peak volcanic activity on the Moon several billion years ago.”

Youthful Appearance

Ina sits near the summit of a gently sloped mound of basaltic rock, leading many scientists to conclude that it was likely the caldera of an ancient lunar volcano. But just how ancient wasn’t clear. While the flanks of the volcano look billions of years old, the Ina caldera itself looks much younger. One sign of youth is its bright appearance relative to its surroundings. The brightness suggests Ina hasn’t had time to accumulate as much regolith, the layer of loose rock and dust that builds up on the surface over time.

Then there are Ina’s distinctive mounds – 80 or so smooth hills of rock, some standing as tall as 100 feet, which dominate the landscape within the caldera. The mounds appear to have far fewer impact craters on them compared to the surrounding area, another sign of relative youth. Over time, it’s expected that a surface should accumulate craters of various sizes at fairly constant rates. So scientists use the number and size of craters to estimate the relative age of a surface. In 2014, a team of researchers did a careful crater-count on Ina’s mounds and concluded that they must have been formed by lava that erupted to the surface within the last 50 to 100 million years.

“That was a really puzzling finding,” Head said. “I think most people agree that the volcano Ina sits on was formed billions of years ago, which means there would have been a pause in volcanic activity for a billion years or more before the activity that formed Ina. We wanted to see if there might be something about geologic structure within Ina that throws off our estimation of its age.”

Not So Young?

The researchers looked at well-studied volcanoes on Earth that might be similar to Ina. Ina appears to be a pit crater on a shield volcano, a gently sloping mountain similar to the Kilauea volcano in Hawaii. Kilauea has a pit crater similar to Ina known as the Kilauea Iki crater, which erupted in 1959.

As lava from that eruption solidified, it created a highly porous rock layer inside the pit, with underground vesicles as large as three feet in diameter and surface void space as deep as two feet. That porous surface, Head and his colleagues say, is created by the nature of the lava erupted in the late stages of events like this one. As the subsurface lava supply starts to diminish, it erupts as “magmatic foam” – a bubbly mixture of lava and gas. When that foam cools and solidifies, it forms the highly porous surface.

The researchers suggest that an Ina eruption would have also produced magmatic foam. And because of the Moon’s decreased gravity and nearly absent atmosphere, the lunar foam would have been even fluffier than on Earth, so it’s expected that the structures within Ina are even more porous than on Earth.

It’s the high porosity of those surfaces that throws off date estimates for Ina, both by hiding the buildup of regolith and by throwing off crater counts.

A highly porous surface, the researchers say, would allow loose rock and dust to filter into surface void space, making it appear as though less regolith has built up. That process would be perpetuated by seismic shaking in the region, much of which is caused by ongoing meteor impacts. “It’s like banging on the side of a sieve to make the flour go through,” Head said. “Regolith is jostled into holes rather than sitting on the surface, which makes Ina look a lot younger.”

Porosity could also skew crater counts. Laboratory experiments using a high-speed projectile cannon have shown that impacts into porous targets make much smaller craters. Because of Ina’s extreme porosity, the researchers say, its craters are much smaller than they would normally be, and many craters might not be visible at all. That could drastically alter the age estimate derived from crater counts.

The researchers estimate that the porous surface would reduce by a factor of three the size of craters on Ina’s mounds. In other words, an impactor that would make a 100-foot-diameter crater in lunar basalt bedrock would make a crater of a little over 30 feet in a foam deposit. Taking that scaling relationship into account, the team gets a revised age for the Ina mounds of about 3.5 billion year old. That’s similar to the surface age of the volcanic shield that surrounds Ina, and places the Ina activity within the timeframe of common volcanism on the Moon.

The researchers believe this work offers a plausible explanation for Ina’s formation without having to invoke the puzzling billion-year pause in volcanic activity.

“We think the young-looking features in Ina are the natural consequence of magmatic foam eruptions on the Moon,” Head said. “These landforms created by these foams simply look a lot younger than they are.”

TOP IMAGE….New research looks at how this strange volcanic caldera on the Moon was formed.NASA/GSFC/ASU

CENTRE IMAGE….A relief image (red and yellow indicate higher elevation) shows Ina’s volcanic mounds rising from the caldera floor. Credit: NASA/GSFC/ASU

LOWER IMAGE….An eruption at Kilauea Iki in 1959 was probably similar to the eruption that formed Ina on the Moon. Credit: USGS

David Attenborough has ancient shrimp fossil named after him

Wildlife documentary maker and national treasure Sir David Attenborough has been honoured with another discovery being named after him.

A 430-million-year-old fossil found ‘frozen in time’ has been called Cascolus Ravitis, Cascolus being the Latin equivalent to the Old English word for Attenborough.

Ravitis refers in part to the Roman name for Leicester (ratae), the University from which the researchers herald and where Attenborough studied, and the word for life (vita).

The ancient crustacean - a distant relative to modern lobsters, shrimps and crabs - measures just nine millimetres in length and was found in a volcanic ash deposit in Herefordshire.

Researchers called the specimen a particularly unique example that “preserves incredible detail including body parts that are normally not fossilised.”

Attending a ceremony at the University of Leicester, Attenborough said: “The biggest compliment that a biologist or palaeontologist can pay to another one is to name a fossil in his honour and I take this as a very great compliment.”

Alongside those from the Department of Geology at Leicester, researchers from the Universities of Oxford, Imperial College London and Yale University also contributed to the discovery.

Recently, a newly discovered species of frog - the Pristimantis attenboroughi, which lives high in the Andes Mountains of South America – was been named after Attenborough.

The broadcast said of that discovery: “One of the nicest compliments one biologist can pay another is to name a new species after him. This is a very great compliment from this scientist.”

Meanwhile, the BBC recently announced a second series of Blue Planet will be hitting TV screens later this year following the success of Planet Earth II.

A pickup truck flees from the pyroclastic flows spewing from the Mount Pinatubo volcano on the island Luzon, Philippines, on June 17, 1991. This was the second largest volcanic eruption of the 20th century. Photo by Alberto Garcia.

Successful predictions at the onset of the climactic eruption led to the evacuation of tens of thousands of people from the surrounding areas, saving many lives, but the surrounding areas were severely damaged by pyroclastic flows, ash deposits, and subsequently, by the lahars caused by rainwaters re-mobilizing earlier volcanic deposits causing extensive destruction to infrastructure and changing the river systems months to years after the eruption.

The effects of the eruption were felt worldwide. It ejected roughly 10,000,000,000 tonnes of magma, and 20,000,000 tonnes SO 2, bringing vast quantities of minerals and metals to the surface environment. It injected more particulate into the stratosphere than any eruption since Krakatoa in 1883. Over the following months, the aerosols formed a global layer of sulfuric acid haze. Global temperatures dropped by about 0.5 °C (0.9 °F) in the years 1991-93, and ozone depletion temporarily increased substantially.

Introduction

Mount Pinatubo (Filipino: Bundok Pinatubo/Bulkang Pinatubo) is an activestratovolcano in the Cabusilan Mountainson the island of Luzon, near the tripoint of the Philippine provinces of Zambales, Tarlac and Pampanga. Its eruptive history was unknown to most before the volcanic activities of 1991. Pinatubo was heavily eroded, inconspicuous, and obscured from view. It was covered with dense forest which supported a population of several thousand indigenous Aetas people.

The volcano’s Plinian / Ultra-Plinianeruption on June 15, 1991 produced the second largest terrestrial eruption of the 20th century after the 1912 eruption of Novarupta in the Alaska Peninsula.Complicating the eruption was the arrival of Typhoon Yunya (Diding), bringing a lethal mix of ash and rain to areas surrounding the volcano. Predictions at the onset of the climactic eruption led to the evacuation of tens of thousands of people from the surrounding areas, saving many lives. Surrounding areas were severely damaged by pyroclastic flows, ash deposits, and, subsequently, by the lahars caused by rainwaters re-mobilizing earlier volcanic deposits. This caused extensive destruction to infrastructure and changed river systems for years after the eruption.

The effects of the eruption were felt worldwide. It ejected roughly 10,000,000,000 tonnes (1.1×1010 short tons) or 10 km3 (2.4 cu mi) of magma, and 20,000,000 tonnes (22,000,000 short tons) SO
2, bringing vast quantities of minerals and metals to the surface environment. It injected more particulate into the stratosphere than any eruption since Krakatoa in 1883. Over the following months, the aerosols formed a global layer of sulfuric acid haze. Global temperatures dropped by about 0.5 °C (0.9 °F) in the years 1991-93,and ozone depletion temporarily increased substantially.

Mt. Pinatubo was an unremarkable and heavily eroded mountain. It was covered in dense forest which supported a population of several thousand indigenous people, the Aeta. They were a hunter-gatherer people who were extremely successful in surviving in the dense jungles.

Watch on the-earth-story.com

I don’t know the person in this, but she does a marvelous job in capturing Yellowstone highlights for a 6 second clip.Mammoth Hot springs, Elk near the north gate, the landscape created by erosion of volcanic deposits, etc.

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Fieldwork along Tabacundo-Guayllabamba Road, North of Quito. This is an activity for the Introduction to Field Methods course.

Exposures along the road show interesting deformations of recent (Cenozoic) sedimentary structures belonging to lacustrine depositional environment. Up to the north, volcanic deposits expose being part of an unit associated to Mojanda volcanic complex.