Posts about geology

Why Wasn’t the Earth Covered in Ice 4 Billion Years Ago – When the Sun was Dimmer

Climate scientists from all over the globe are now able to test their climate models under extreme conditions thanks to Professor Minik Rosing, University of Copenhagen. Rosing has solved one of the great mysteries and paradoxes of our geological past, namely, “Why the earth’s surface was not just one big lump of ice four billion years ago when the Sun’s radiation was much weaker than it is today.” Until now, scientists have presumed that the earth’s atmosphere back then consisted of 30% carbon dioxide (CO2) which ensconced the planet in a protective membrane, thereby trapping heat like a greenhouse.

The faint early sun paradox
In 1972, the late, world famous astronomer Carl Sagan and his colleague George Mullen formulated “The faint early sun paradox. ” The paradox consisted in that the earth’s climate has been fairly constant during almost four of the four and a half billion years that the planet has been in existence, and this despite the fact that radiation from the sun has increased by 25-30 percent.

The paradoxical question that arose for scientists in this connection was why the earth’s surface at its fragile beginning was not covered by ice, seeing that the sun’s rays were much fainter than they are today. Science found one probable answer in 1993, which was proffered by the American atmospheric scientist, Jim Kasting. He performed theoretical calculations that showed that 30% of the earth’s atmosphere four billion years ago consisted of CO2. This in turn entailed that the large amount of greenhouse gases layered themselves as a protective greenhouse around the planet, thereby preventing the oceans from freezing over.

Mystery solved
Now, however, Professor Minik Rosing, from the Natural History Museum of Denmark, and Christian Bjerrum, from the Department of Geography and Geology at University of Copenhagen, together with American colleagues from Stanford University in California have discovered the reason for “the missing ice age” back then, thereby solving the sun paradox, which has haunted scientific circles for more than forty years.

Professor Minik Rosing explains, “What prevented an ice age back then was not high CO2 concentration in the atmosphere, but the fact that the cloud layer was much thinner than it is today. In addition to this, the earth’s surface was covered by water. This meant that the sun’s rays could warm the oceans unobstructed, which in turn could layer the heat, thereby preventing the earth’s watery surface from freezing into ice. The reason for the lack of clouds back in earth’s childhood can be explained by the process by which clouds form. This process requires chemical substances that are produced by algae and plants, which did not exist at the time. These chemical processes would have been able to form a dense layer of clouds, which in turn would have reflected the sun’s rays, throwing them back into the cosmos and thereby preventing the warming of earth’s oceans. Scientists have formerly used the relationship between the radiation from the sun and earth’s surface temperature to calculate that earth ought to have been in a deep freeze during three billion of its four and a half billion years of existence. Sagan and Mullen brought attention to the paradox between these theoretical calculations and geological reality by the fact that the oceans had not frozen. This paradox of having a faint sun and ice-free oceans has now been solved.”

CO2 history iluminated
Minik Rosing and his team have by analyzing samples of 3.8-billion-year-old mountain rock from the world’s oldest bedrock, Isua, in western Greenland, solved the “paradox”.

But more importantly, the analyses also provided a finding for a highly important issue in today’s climate research – and climate debate, not least: whether the atmosphere’s CO2 concentration throughout earth’s history has fluctuated strongly or been fairly stable over the course of billions of years.

“The analyses of the CO2-content in the atmosphere, which can be deduced from the age-old Isua rock, show that the atmosphere at the time contained a maximum of one part per thousand of this greenhouse gas. This was three to four times more than the atmosphere’s CO2-content today. However, not anywhere in the range of the of the 30 percent share in early earth history, which has hitherto been the theoretical calculation. Hence we may conclude that the atmosphere’s CO2-content has not changed substantially through the billions of years of earth’s geological history. However, today the graph is turning upward. Not least due to the emissions from fossil fuels used by humans. Therefore it is vital to determine the geological and atmospheric premises for the prehistoric past in order to understand the present, not to mention the future, in what pertains to the design of climate models and calculations,” underscores Minik Rosing.

Full press release from the University of Copenhagen in Denmark.

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New Largest Known Cave

photo of world's largest known cave,  in Vietnam

The world’s largest cave

A British caving team believe they have discovered the world’s largest cave passage in the heart of the Vietnamese jungle. The rocky passage is 150metres long and measures a towering 200metres in height – seven times as high as the vaulted ceiling of York Cathedral.

Called Hang Son Doong (Mountain River Cave) it is believed to be almost twice the size of the current record holder

The cave was originally discovered in 1991 by a Vietnamese Jungle man called Ho Khanh. However Mr Spillane said no-one had entered if before because ‘it emitted a frightful wind and noise which was due to a large underground river’.

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Does the Earth Have Two Cores?

Did Earth’s Twin Cores Spark Plate Tectonics?

a new theory aims to rewrite it all by proposing the seemingly impossible: Earth has not one but two inner cores.

The idea stems from an ancient, cataclysmic collision that scientists believe occurred when a Mars-sized object hit Earth about 4.45 billion years ago. The young Earth was still so hot that it was mostly molten, and debris flung from the impact is thought to have formed the moon.

Haluk Cetin and Fugen Ozkirim of Murray State University think the core of the Mars-sized object may have been left behind inside Earth, and that it sank down near the original inner core. There the two may still remain, either separate or as conjoined twins, locked in a tight orbit.

Their case is largely circumstantial and speculative, Cetin admitted. “We have no solid evidence yet, and we’re not saying 100 percent that it still exists,” he said. “The interior of Earth is a very hard place to study.”

The ancient collision is a widely accepted phenomenon. But most scientists believe the incredible pressure at the center of the planet would’ve long since pushed the two cores into each other.

I must say two cores seems very far-fetched to me. But it is another great example of the scientific discovery process and an interesting idea.

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A Microscopic Layer of Diamonds Beneath the Surface of North America

Diamonds show comet struck North America, scientists say

A discovery of microscopic diamonds a few feet beneath the surface of North America reveals that a comet caused a cataclysm of fire, flood and devastation nearly 13,000 years ago that extinguished mammoths and mastodons and dealt a blow to early civilization, scientists said Friday.

The nanodiamonds, so small that they are barely visible in an electron microscope, are thought to be remnants of that comet, which would have hit about 65 million years after the much larger collision that wiped out the dinosaurs.

Battered by fire and ice, as many as 35 species of mammals, including American camels, the short-faced bear, the giant beaver, the dire wolf and the American lion, either immediately vanished or were so depleted in number that humans hunted them to extinction.

The humans, a Paleo-Indian grouping known as the Clovis culture for the distinctive spear points they employed, suffered a major population drop, disappearing in many areas for hundreds of years.

gems can only be created under the extreme temperatures and pressures of a massive explosion, such as a comet striking the Earth’s surface.

“There’s no other way we can interpret the presence of these diamonds other than an extraterrestrial impact,” said James Kennett, a paleooceanographer.

Such an impact would be the most likely source of nanodiamonds, critics agreed. But many argued that the one-page paper in Science did not provide enough evidence to support the authors’ claim.

“Nanodiamonds could be a good indicator of an impact event . . . but after reading the paper, I wasn’t convinced they found diamonds,” said physicist Tyrone Daulton of Washington University in St. Louis. “Maybe they found diamonds and maybe they didn’t.”

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Quake Lake Danger

Quakes lakes risk ‘slurry tsunami’

This month’s 7.9 magnitude tremor spawned 34 so-called quake lakes, according to the International Association of Hydraulic Engineering and Research expert. The vast pools of water were created when the earthquake triggered landslides down plunging valleys, clogging rivers and turning them into fast-rising lakes. Twenty-eight quake lakes are at risk of bursting, according to Chinese state media agency Xinhua. But the one at Tangjiashan – on the Jianjiang river above the town of Beichuan – is the most precarious.

The delicate, tortuous work involves heavy machinery gingerly shifting debris from the dam, and engineers blasting dynamite to carefully punch holes in the mountain of rubble and soil – although experts warn this risks further destabilising the structure. Nearly 160,000 people in the disaster zone have already been evacuated in case the Tangjiashan quake lake bursts.

Troops and engineers are racing to carve a 500 metre (1,640 ft) channel out of the landscape and divert the water towards the Fujiang river. They aim to complete the giant sluice and begin draining the 300 million cubic metre capacity lake within 10 days. “Once the water begins to flow over the top of the dam there’s nothing you can do to stop it,” said Dr Alex Densmore, of Durham University’s Institute of Hazard and Risk Research.

Little wonder then that Premier Wen Jiabao says he regards draining the swelling quake lakes at China’s ground zero as the nation’s most urgent task.

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Wabash Valley, Illinois Earthquakes

USGS on the recent earthquakes occurred in the Wabash Valley Seismic

These earthquakes occurred in the Wabash Valley Seismic zone. The earthquakes in this zone are scattered over a large area of southeastern Illinois and southwest Indiana. The zone had at least eight prehistoric earthquakes over the past 20,000 years with estimated magnitudes ranging from about 6.5 to 7.5, based on geologic evidence. Earthquakes of the size of the recent quake (Mw 5.2) can produce smaller aftershocks over the following days. A few might be large enough to be felt. Typically, earthquakes of this size (Mw 5.2) can cause light damage within a few tens of miles from the epicenter. Central and eastern US earthquakes generally shake areas about 10 times as large as those that occur in California. It is not surprising that this earthquake was felt as far south as Florida.

The Wabash Valley Seismic zone is adjacent to the more seismically active New Madrid seismic zone on the seismic zone’s north and west. The recent earthquake is also within the Illinois basin – Ozark dome region that covers parts of Indiana, Kentucky, Illinois, Missouri, and Arkansas and stretches from Indianapolis and St. Louis to Memphis. Moderately frequent earthquakes occur at irregular intervals throughout the region. The largest historical earthquake in the Illinois Basin region (magnitude 5.4) damaged southern Illinois in 1968. Moderately damaging earthquakes strike somewhere in the region each decade or two, and smaller earthquakes are felt about once or twice a year.

Earthquakes in the central and eastern U.S., although less frequent than in the western U.S., are typically felt over a much broader region. East of the Rockies, an earthquake can be felt over an area as much as ten times larger than a similar magnitude earthquake on the west coast.

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A New Epoch – Anthropocene

Has Earth entered a new epoch?

Geologists wonder if they should add a new epoch to the geological time scale. They call it the Anthropocene – the epoch when, for the first time in Earth’s history, humans have become a predominant geophysical force. Naming such a new epoch would also recognize that humans now share responsibility with natural forces for the state of our planet’s ecological environment.

Geologists have been using the term informally for at least half a decade. Now members of the Stratigraphy Commission of the Geological Society of London have laid out the case for giving the term official scientific status.

They make a good point I think.

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Himalayas Geology

Mystery of the Himalayas Solved:

The mystery of why the Himalaya mountains and the Tibetan plateau are the highest in the world has at last been answered, with the discovery of a gigantic chunk of rock slowly sinking towards the centre of the Earth. When the massive slab – up to eight times the area of the UK and as thick as a dozen Everests on top of each other – dropped off, the lighter crust above it rebounded upwards like a cork released under water, geophysicists say. This “sudden uplift” would have raised the Himalayas by as much as 2km (1.24 miles) to their present height.

If not for the surge, Sir Edmund Hillary and Sherpa Tenzing Norgay might have found themselves reaching the “roof of the world” by conquering Aconcagua (6,962m) in Argentina while Everest languished at a mere 6,848m above sea level, 2,000m below its actual peak. The discovery of the missing mantle – the cold, heavy rock beneath the crust – was revealed last week by Professor Wang-Ping Chen at the University of Illinois, whose team used more than 200 super-sensitive seismometers strung across the Himalayas, from India deep into Tibet.

But some scientists remain sceptical. One geologist at Cambridge, who wanted to remain anonymous because he hadn’t yet read Professor Chen’s paper, suggested that the slab could be the remains of the Tethys Ocean plate. Professor England counters that both the Asian and Indian plates have moved north since then

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