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Jökulhlaup

The Ice Age fascinates me. Tectonic plates take millions of years to change the earth, but a few hundred million tons of ice and water can do it in a few thousand. Or sometimes, if the conditions are just right, things happen a lot faster.

When a glacier melts, the water usually flows away as a stream or river from the base of it. However, if the water is dammed and released, or if something like a volcano causes catastrophic melting, that stream can turn into a devastating flood.

This is what is known as a jökulhlaup (pronounced yoo-kul-hloo-ee-p) or glacial outburst flood. They’re well-known in Iceland (where we get “jökulhlaup” from) because of the numerous glaciers and volcanoes, but can occur anywhere where glaciers exist and can be very dangerous. The 1755 Mýrdalsjökull jökulhlaup may have released more cubic meters of water per second than the Amazon river.

During the last ice age these kinds of massive outbursts were very common. As the planet warmed, immense lakes of meltwater formed in the middle of the retreating glaciers, eventually releasing unimaginably large floods. It’s now accepted that the bizarre geology of the channelled scablands was the result of just a handful of these outbursts.

Jökulhlaups – very dangerous, very interesting.

Source: http://en.wikipedia.org/wiki/J%C3%B6kulhlaup

 
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Posted by on October 20, 2013 in Natural History

 

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Pangaea Ultima

I believe that every child looking at a globe has noticed it at some point or another. That weird coincidence between Africa’s and South America’s coastlines – how they kind of look like they fit together, if you smushed them up. Like the pieces of a jigsaw puzzle. I remember finding a map and cutting the two continents out, just to see how they’d line up. I didn’t know it at the time, but I was, on my own, recreating the first steps towards the theory of continental drift.

In fact, the man who started the idea, a 16th century cartographer named Abraham Ortelius, started with the same observation, although the theory of plate tectonics wasn’t conclusively proven until the early 1950’s when a group of scientists convinced the US Navy to drag a magnetometer behind a submarine, charting the magnetic signatures and history of the sea floor.

The continents are still moving today, albeit very slowly, about four inches a year at most. Thanks to science we actually know the direction and speed these plates travel. Currently the Atlantic Ocean seems bent on spreading wider, most of North America is being shoved into the Rockies, India continues to drive northwards into Asia, and Australia want to move northeast. With a few of educated guesses we can even determine where they will be far into the future.

From scotese.com

The above map depicts on the more popular possibilities, Pangaea Ultima. As the idea goes, the Atlantic Ocean will eventually stop widening and begin to shrink while the Pacific and Indian Oceans start to drastically expand, eventually pushing South America, North America, Europe, Africa, and Asia into one huge landmass. The Mediterranean Sea will be squashed into an incredible mountain range whose height will dwarf the Himalayas of today. Antarctica will sidle northwards for a bit and crash into Australia, only to eventually backtrack and return to its polar domain.

By that time the human species will likely no longer be around to see Pangaea Ultima, but it’s not like it’ll be permanent either. Eventually, plate tectonics will rip the supercontinent apart again, scattering the continents back around the globe.

 
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Posted by on October 23, 2012 in Uncategorized

 

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The Yellowstone Supervolcano

Yellowstone National Park is famous for its natural grandeur. Forests embroider immense canyons. Sulfur and mineral crystals engrail the edges of hot springs with gemstone-like colors. Wolves and bison roam, relatively unimpeded by the towns, roads, and fences that so callously divided the West. It feels eternal, like it must exist outside of our normal scope of time, something both eternal and ephemeral. But ask anyone in the US Geological Service, and they’ll tell you a different story about Yellowstone. About how it is one of the most dynamic and possibly most destructive places on the planet.

Yellowstone National Park sits directly over what is known as the Yellowstone Caldera, also called the Yellowstone Supervolcano. And it deserves its title of supervolcano. The caldera, the crater formed after an eruption, is more than forty miles across. With the last major eruption, which took place sometime around 600,000 years ago, Yellowstone ejected well over 240 cubic miles of debris (Mount St. Helen’s, the United State’s most destructive volcanic explosion ever recorded, ejected about 0.6 cubic miles). The ash cloud would have covered at least half of the continental USA and drastically altered the global climate for at least two decades.

Spread of ash and tephra falls after an eruption.

Fun fact, supervolcanoes are included in Wikipedia’s Risks to Human Civilization page.

But, grandstanding aside, Yellowstone is not very likely to erupt any time soon. These kinds of super eruptions are incredibly rare, only occurring once every one to two millions years. Plus, scientists have been monitoring Yellowstone for some time now and we’d have at least several hundred years of forewarning.

Oh, one last thing. Even though we’re pretty safe, know that the land is still undergoing change. A report in 2011 showed that the ground in certain spots of the caldera was starting to rise almost as much as a foot in some places.

Just thought you might like to know.

Sources: USGS, vulcan.wr.usgs.gov, National Geographic,

 
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Posted by on June 12, 2012 in Natural History

 

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Nature’s Nuclear Reactor

I’ve always been drawn to the nuclear age. There’s something to America’s vast and sudden post-war wealth, the growingly divergent half-McCarthy half-hippy culture, and rising technology that seems effortlessly and inherently American. But we as a country seem to be in love with things that are already half-departed. The cowboy only became a national symbol well after the range was fenced in. Similarly, the uranium reactor seems like it’s on the way out already. Germany just announced a planned retirement of its nuclear reactors. But even though the yellow-and-black triad may less than a hundred years old, nuclear reactors are actually far more ancient than most people realize.

Okay, a quick crash course. Nuclear reactors are powered by nuclear fission. In fission, radioactive atoms will sometimes shed a neutrons as they ultimately decay into more stable isotopes. The uranium atoms are usually too far apart and the neutron is usually absorbed by other surrounding elements, but if the uranium atoms are condensed enough it will actually set off a chain reaction. Think of it like tossing a single lit cracker into a fireworks factory. Each time something goes off it only makes the reaction stronger. Small cracker, big dense pile of fireworks, lots of energy. Small neutron, big dense pile of uranium atoms, lots of energy. Yeah? Yeah. (Okay, so it’s actually a lot more complicated than that, but you get the idea).

Anyways, back in 1956 someone named Paul Kazuo Kuroda hypothesized that this arrangement needn’t be man-mand and could actually be possible in nature. And sixteen years later, deep in the heart of Gabon, he was proven right. The French physicist Francis Perrin found evidence that one particular uranium mine was actually the home of an intermittent 1.7 billion year old reactor that must have run for more than a million years. The reactor had long run out of steam, but it’s still-radioactive by-products are still around today and still available for study.

Source: geology.about.comhttp://www.ans.org/pi/np/oklo/, Wikipedia

 
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Posted by on May 15, 2012 in Natural History

 

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Snowball Earth

We are all familiar with the idea of an ice age. But as a rule, even in the worst of winters the tropics stay warm and ice-free. But then why are geologists finding the signature evidence of glaciers throughout previously tropical areas ? And what kind of Earth could exist that would allow even the tropics to freeze? One of the most intriguing explanations is that, in our distant past, the Earth itself completely froze over, a hypothesis known as Snowball Earth.

It would start as a normal period of global cooling, much like what happened 12,000 years ago in the Younger Dryas period. In that case the dip in temperatures was likely caused by disruption of ocean currents, but anything could start it off. Glaciers would swell and progress southward. For a little while it would look like any other ice age. But a quirk in our planet’s climate would change all of that soon enough and plunge us into a seemingly never-ending freeze.

Winter is coming...

Ice, you see, is brighter and more reflective than either land or ocean water. Anyone who has experienced snow blindness knows this. As the glaciers spread, the reflectivity (or albedo) of the surface of the earth increases. The problem is that the more reflective ice shunts more sunlight and more importantly heat back into space. Normally other climate factors can correct this, but only up to a point. After that the process only accelerates itself, the ice creating lower temperatures, the lower temperatures creating more ice. It would only stop once the entire globe was frozen. This would last for as long as thirty million years.

And the thing is? According to the hypothesis, this didn’t just happen once. At least three periods of deep glaciation have been identified, the latest during the Ediacaran period, just as life was beginning to diversify into recognizable forms. Funnily enough, this may have actually accelerated evolutionary change due to the extreme competition for what little resources survived (and the extinction of less fit lineages of life).

Eventually, however, everything must come to an end. Once again, quirks of the climate cycle would effect the entire globe. Carbon dioxide, the most famous greenhouse gas, is normally removed from the atmosphere by two means: photosynthesis and open water. But with life barely hanging on in shallow icemelts or geothermal hotspots, photosynthesis would be virtually nonexistent. Furthermore, Ice sheets would also prevent any contact with the ocean. The gas couldn’t go anywhere, but volcanoes and other geothermal activities would ensure a steady income of it. The CO2 would slowly build and build and build.

Eventually, the temperatures would rise up again and the cycle would reverse itself. Open water would appear and absorb sunlight again, continuing to drive up temperatures. Life, meanwhile, would find that conditions would sudden become much more favorable. Temperatures would climb, oceans would open, and the melting glaciers would drop tons of locked nutrients into the sea. The ocean would become chock full of resources for the newly freed life and they would go nuts in one of the single biggest evolutionary events ever, a period known as the Cambrian Explosion.

Winter is leaving...

Luckily for life, there have been no other Snowball Earths since then. But the quirks and mechanisms that allowed it to happen once still exist today. It is not inconceivable that sometime in the far future the Earth may once again be ruled by ice.

Sources: BBC NatureNational Geographic, onorbit.comknowyourmeme.com, Wikipedia

 
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Posted by on October 22, 2011 in Natural History

 

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