Adventures on Earth For January 26 edition of The Review
By George E. Beetham Jr.
Africa is splitting apart. Recently scientists have found that the rifting of Africa is happening at a faster pace than had been expected.
The rifting of Africa is not news. The Rift Valley that parallels the eastern Africa coast has been known even before plate tectonics explained the dynamics of how continents move together and break apart.
From Ethiopia down through Tanzania, the rift valley is marked by lower elevation, lakes, and volcanoes.
Mount Kilimanjaro is one of the volcanoes that is part of the rift.
What is happening is that the continental crust of East Africa is being stretched apart by convection currents in the mantle – the region of hot viscous rock lying just under the hard crust.
Some geologists suggest the plates are pulled apart by the weight of heavy oceanic plates being pulled back into the mantle.
In any event, as the crust is stretched a block of it eventually drops down below the level of the land on either side of the rift valley. This is called a block fault, or a normal fault.
Eventually, as land drops below sea level, the sea begins to pour into the rift valley and a new ocean is formed.
The African rift valley joins another fault running the length of the Red Sea. The Red Sea was formed from a rift valley that dropped below sea level millions of years ago.
Faults that cause continental crust to fracture apart begin in a three-way fault junction. The three-way junction for the Red Sea and East Africa Rift Valley is located in the Red Sea just off the coast of northern Ethiopia.
In northern Ethiopia, the Afar Depression lies below sea level. It is separated from the Red Sea by a ridge that rises above sea level, or the sea would have already intruded into Ethiopia.
Within the Afar Depression the geology is similar to Iceland, and in some ways to Yellowstone. The crust is very thin here, so crustal rock is very hot. Vents spew lava and water heated geothermally pools, evaporates, and leaves salts and minerals behind.
The Danakil Desert of the Afar Depression lies some 500 feet below sea level, again protected from inundation by the ridge bordering the Red Sea.
In the rift valley, the land on either side of the fault is moving apart at the rate of about .8 of an inch a year. The result of this is earthquakes and volcanic eruptions as the block fault continues to drop land within the rift.
Eventually all of this activity will cause the ridge that currently keeps the Red Sea out to fracture and begin to split apart. The sea will fill in. Then the rifting of Africa will continue apace until a new sea parts the two pieces of the continent.
Geologists are watching this process as it unfolds. The sea could intrude anytime. A violent earthquake would start the process. It could happen in years, decades, or millions of years.
The fact is, we do not know how quickly the process will occur because we have never seen it happen in the time humans have been on the planet.
We understand the dynamics of plate tectonics, but actually seeing a rift open to the sea has never been seen by human eyes.
It could answer a lot of questions geologists have of just how these tectonic events play out. We have seen how plates collide to push up mountains, how oceanic plates subduct into the mantle, and how plates move past one another.
We can measure the results of these events and say mountains grow by so many inches over a certain period of time.
So geologists who study tectonics likely hope the process takes place during their lifetimes. The fact is, we might or might not see it in our lifetimes, but it is likely that some humans will get to see the birth of a new ocean.
Phacops Rana
Wednesday, January 26, 2011
It’s that La Nina
Adventures on Earth for January 19 edition of The Review
By George E. Beetham Jr.
Severe weather has been responsible for disasters around the world: flooding in Australia, landslides in Brazil, cold in Europe, snow and cold in the American southeast.
Meanwhile, the Arctic is enjoying somewhat warmer than normal temperatures.
Much is due to the current La Nina weather pattern. Here in the Northeast and Mid-Atlantic regions, that means more moisture is in the air, hence more precipitation.
Cold air, meanwhile, has been flowing southward from the Arctic. This has put the Mid-Atlantic region north of the jet stream, the boundary between colder air and warmer air.
Low pressure riding along the jet stream has brought snowfall. If the jet should move northward, we will get rain (rain is in the forecast for this week, but after a snowfall).
These storms are known as nor’easters. Circulation around the low is counter-clockwise, so as the lows approach the Atlantic Coast, the low picks up relatively warm and moisture-laden ocean air and circulates it east and southeast over the Mid-Atlantic.
It is at this point that nor’easters can be their most problematic. This winter, continental air had been north of the jet stream, hence it is colder. As the moisture flows off the ocean it meets the cold air and the moisture precipitates out as snow.
While we might grumble about having to shovel snow, we are getting off easy. The La Nina effects have reduced food crops around the world, raising prices and causing concern, MSNBC reported last Friday.
Between too much rain where it is not needed and not enough where it is needed, crops are either subjected to flood or drought. Coupled with the fact that some 30 percent of the U.S. corn crop is being diverted to ethanol production, supplies are short around the world.
The concern is over the potential long term results of the weather anomalies. The National Weather Service Climate Prediction Center is predicting the La Nina will last into spring at least with concern it could stretch into summer.
The center believes, however, that the La Nina will slowly weaken over that time.
In the meantime, we can expect a nearly constant parade of nor’easters moving across the region bringing snow when fronts stall south of us and rain when fronts stall north of us.
With nor’easters, forecasters have a difficult time making forecasts. Movement of tens of miles in the path they take can be the difference between a blizzard and snow showers.
Another factor is the speed at which the weather patterns move. A nor’easter that moves slowly will bring more snow than a nor’easter that moves past us quickly.
And if the nor’easter should stall, expect a blizzard.
Most of the storms this winter have moved through fairly quickly. We got about 12 inches of snow back in December. Subsequent storms have brought less.
This week’s changing pattern is supposed to bring us rain, but the temperatures normally drop in late January to produce the coldest weather of the year.
Lows in the low teens occurred last week and the temperature is again expected to drop back into the teens later this week.
Clearly, neither winter nor La Nina is loosening their grips to any great degree.
The warming trend should begin late next month and increase during March.
Depending on how much the La Nina weakens, spring will follow as it always does, sooner or later, groundhog or no groundhog.
By George E. Beetham Jr.
Severe weather has been responsible for disasters around the world: flooding in Australia, landslides in Brazil, cold in Europe, snow and cold in the American southeast.
Meanwhile, the Arctic is enjoying somewhat warmer than normal temperatures.
Much is due to the current La Nina weather pattern. Here in the Northeast and Mid-Atlantic regions, that means more moisture is in the air, hence more precipitation.
Cold air, meanwhile, has been flowing southward from the Arctic. This has put the Mid-Atlantic region north of the jet stream, the boundary between colder air and warmer air.
Low pressure riding along the jet stream has brought snowfall. If the jet should move northward, we will get rain (rain is in the forecast for this week, but after a snowfall).
These storms are known as nor’easters. Circulation around the low is counter-clockwise, so as the lows approach the Atlantic Coast, the low picks up relatively warm and moisture-laden ocean air and circulates it east and southeast over the Mid-Atlantic.
It is at this point that nor’easters can be their most problematic. This winter, continental air had been north of the jet stream, hence it is colder. As the moisture flows off the ocean it meets the cold air and the moisture precipitates out as snow.
While we might grumble about having to shovel snow, we are getting off easy. The La Nina effects have reduced food crops around the world, raising prices and causing concern, MSNBC reported last Friday.
Between too much rain where it is not needed and not enough where it is needed, crops are either subjected to flood or drought. Coupled with the fact that some 30 percent of the U.S. corn crop is being diverted to ethanol production, supplies are short around the world.
The concern is over the potential long term results of the weather anomalies. The National Weather Service Climate Prediction Center is predicting the La Nina will last into spring at least with concern it could stretch into summer.
The center believes, however, that the La Nina will slowly weaken over that time.
In the meantime, we can expect a nearly constant parade of nor’easters moving across the region bringing snow when fronts stall south of us and rain when fronts stall north of us.
With nor’easters, forecasters have a difficult time making forecasts. Movement of tens of miles in the path they take can be the difference between a blizzard and snow showers.
Another factor is the speed at which the weather patterns move. A nor’easter that moves slowly will bring more snow than a nor’easter that moves past us quickly.
And if the nor’easter should stall, expect a blizzard.
Most of the storms this winter have moved through fairly quickly. We got about 12 inches of snow back in December. Subsequent storms have brought less.
This week’s changing pattern is supposed to bring us rain, but the temperatures normally drop in late January to produce the coldest weather of the year.
Lows in the low teens occurred last week and the temperature is again expected to drop back into the teens later this week.
Clearly, neither winter nor La Nina is loosening their grips to any great degree.
The warming trend should begin late next month and increase during March.
Depending on how much the La Nina weakens, spring will follow as it always does, sooner or later, groundhog or no groundhog.
Parts of a larger process
Adventures on Earth for January 12 edition of The Review
By George E. Beetham Jr.
Last week we discussed the melting and refreezing of the Antarctic ice sheet and how it might react to global warming.
There are two issues that we need to keep in mind. First, the temperature has been increasing when measured over decadal time. Second, the ice in Antarctica is slowly melting and giving way.
The collapse of the Larsen B ice shelf in the 1990s is the forerunner of more to come. Ice has been fastened to Antarctica for hundreds of thousands of years. But ice has been separating from the continent.
Polar ice does not melt from above. It melts as sea water heats up, from below.
Beneath the sea ice there are large numbers of krill, tiny crustaceans that live just under the ice. Fish feed on krill, and other creatures, including penguins, feed on the fish.
It is a food chain that has existed for hundreds of thousands of years and constitutes a major biological part of the Antarctic ecosystem.
We don’t think of ice as being an ecosystem, but it is. As sea ice melts, there is concern that krill may disappear. If that happens, the entire biologic ecosystem is likely to collapse.
Other than aesthetics, that would not affect humans. But melting ice will affect us as sea levels rise as much as 200 feet.
The effects will not become apparent today, tomorrow, or even next year. But as the sea continues to warm, collapse of the polar ice caps is likely to occur quickly.
In the Arctic, sea ice is melting relatively quickly. People who live and work in the Arctic have noticed it. The effects are inescapable. A whole host of Arctic-dwelling creatures are endangered. If change comes quickly, creatures have no time to adapt. Adaptation is one way for life to avoid extinction.
On land, the Antarctic ice sheet is also melting from below. Water trickles through the ice until it hits bedrock below. There it acts as a lubricant, propelling glacial ice down slope toward the sea. The same thing is happening in Greenland.
This is happening as we discuss it. It is not conjecture that it might occur five or six decades from now. It is happening.
As polar ice melts and sea levels increase, there will be consequences for humans. First, people living in coastal areas will be forced to move to higher ground. Secondly, as sea levels increase, there will be less inhabitable land on which to live, work, and farm.
There will be less fresh water available as the land surface shrinks. As one commentator has suggested, we can live without coal, oil, gas. We cannot live without water.
All the polar ice will melt into the sea, picking up salinity. But it will also dilute salty sea water, and that is likely to affect the ocean currents that carry equatorial warm water toward the poles and cold polar water toward the equator. That, in turn, could trigger another ice age.
Humans may be adaptable and able to cope with changing climate. The question we face for our future and the futures of our descendants is whether our food sources will adapt.
Native Americans tell us the world is interconnected. Science tells us the same thing. As species go extinct, that affects other species, particularly if the extinct species is a food source for creatures up the chain.
As resources become scarce, wars are likely to be fought to either protect one’s resources or to take resources that are needed from others who have them.
What is happening in Antarctica affects all of us, whether we choose to believe what is happening or not. It is just one more part of a larger process. It tells us that we need to prepare to deal with what is to come.
By George E. Beetham Jr.
Last week we discussed the melting and refreezing of the Antarctic ice sheet and how it might react to global warming.
There are two issues that we need to keep in mind. First, the temperature has been increasing when measured over decadal time. Second, the ice in Antarctica is slowly melting and giving way.
The collapse of the Larsen B ice shelf in the 1990s is the forerunner of more to come. Ice has been fastened to Antarctica for hundreds of thousands of years. But ice has been separating from the continent.
Polar ice does not melt from above. It melts as sea water heats up, from below.
Beneath the sea ice there are large numbers of krill, tiny crustaceans that live just under the ice. Fish feed on krill, and other creatures, including penguins, feed on the fish.
It is a food chain that has existed for hundreds of thousands of years and constitutes a major biological part of the Antarctic ecosystem.
We don’t think of ice as being an ecosystem, but it is. As sea ice melts, there is concern that krill may disappear. If that happens, the entire biologic ecosystem is likely to collapse.
Other than aesthetics, that would not affect humans. But melting ice will affect us as sea levels rise as much as 200 feet.
The effects will not become apparent today, tomorrow, or even next year. But as the sea continues to warm, collapse of the polar ice caps is likely to occur quickly.
In the Arctic, sea ice is melting relatively quickly. People who live and work in the Arctic have noticed it. The effects are inescapable. A whole host of Arctic-dwelling creatures are endangered. If change comes quickly, creatures have no time to adapt. Adaptation is one way for life to avoid extinction.
On land, the Antarctic ice sheet is also melting from below. Water trickles through the ice until it hits bedrock below. There it acts as a lubricant, propelling glacial ice down slope toward the sea. The same thing is happening in Greenland.
This is happening as we discuss it. It is not conjecture that it might occur five or six decades from now. It is happening.
As polar ice melts and sea levels increase, there will be consequences for humans. First, people living in coastal areas will be forced to move to higher ground. Secondly, as sea levels increase, there will be less inhabitable land on which to live, work, and farm.
There will be less fresh water available as the land surface shrinks. As one commentator has suggested, we can live without coal, oil, gas. We cannot live without water.
All the polar ice will melt into the sea, picking up salinity. But it will also dilute salty sea water, and that is likely to affect the ocean currents that carry equatorial warm water toward the poles and cold polar water toward the equator. That, in turn, could trigger another ice age.
Humans may be adaptable and able to cope with changing climate. The question we face for our future and the futures of our descendants is whether our food sources will adapt.
Native Americans tell us the world is interconnected. Science tells us the same thing. As species go extinct, that affects other species, particularly if the extinct species is a food source for creatures up the chain.
As resources become scarce, wars are likely to be fought to either protect one’s resources or to take resources that are needed from others who have them.
What is happening in Antarctica affects all of us, whether we choose to believe what is happening or not. It is just one more part of a larger process. It tells us that we need to prepare to deal with what is to come.
Monday, January 3, 2011
Antarctica’s changing climate
Adventures on Earth for the January 5 edition of The Review
By George E. Beetham Jr.
When Antarctica’s Larsen Ice Shelf broke up between 1995 and 2002, scientists became concerned that global warming might hasten the melting of ice on the polar continent, raising sea levels perhaps hundreds of feet.
By 2006, the Antarctic Geologic Drilling Project (Andrill) set out to answer the questions global warming posed.
The idea was to drill through the ice sheet into the sea below and then drill into the sea floor below that. Scientists hoped to study sediments to learn about Antarcticclimate change over millions of years.
Until Andrill, scientists had drilled into the ice to study climate. But the ice sheets and shelves that cover Antarctica only go back only about 800,000 years. Drilling into the earth below the sea would provide cores dating far earlier than that.
The cores that were obtained are still being studied, and more drilling projects are taking place. Still, studies to date tell a fascinating story about Antarctica and climate change around the world.
Antarctica contains about 90 percent of the Earth’s ice according to an Andrill report. The total volume is estimated at 29 million cubic kilometers to 32 million cubic kilometers.
If all that ice should melt, sea levels could rise as much as 200 feet. For reference, that would cover nearly all of Philadelphia with water.
Andrill is a multi-national effort staffed by researchers from Germany, Italy, New Zealand, and the United States. Andrill scientists have learned that Antarctica was not always covered in ice, even during the recent ice age.
Some 190 million years ago, Antarctica was located closer to the Equator. Connected to present day Australia, India, and East Africa in the supercontinent Pangea, the climate was warm enough to support vegetation and animal life.
As Pangea broke up, Antarctica drifted south toward the South Pole. For the past 100 million years it has been roughly in its present position. That would seem to indicate that it was covered by ice during that entire time.
That is not the case. Several times the continent has warmed sufficiently to allow plant life to return. Volcanoes erupted, depositing fine ash on top of ice. And marine creatures associated with warm oceans were found in the sediments.
In other words, Antarctica warmed and cooled several times in the past 100 million years.
The present ice sheet did not begin to form until 34 million years ago. Then, during the Pliocene about 5 million years ago, the continent warmed up yet again.
Scientists have discovered remnants of peat moss, wood fragments, and leaves that were buried in sediments, but flash frozen. They never had a chance to become fossilized into coal. The fragments are the original plants.
In the Mullens Valley of East Antarctica, volcanic ash that settled on top of the ice sheet is pristine. The ice never melted and the ash never formed into rock. The ash is millions of years old and evidence that volcanic activity occurred about that time.
Evidence of the Pliocene warming is found around the Earth. In New Zealand, sediments include fossils of marine creatures, indicating the sea level was some 60 feet higher. Along the shores of the Chesapeake Bay, the same evidence is found.
This indicates that the Antarctic ice sheet has melted at least partially in the past 30 million years and will likely do so again.
These variations were natural cycles in Earth’s climate. Current concerns over global warming look to human burning of fossil fuels as a warming influence.
Next week: Meltdown
By George E. Beetham Jr.
When Antarctica’s Larsen Ice Shelf broke up between 1995 and 2002, scientists became concerned that global warming might hasten the melting of ice on the polar continent, raising sea levels perhaps hundreds of feet.
By 2006, the Antarctic Geologic Drilling Project (Andrill) set out to answer the questions global warming posed.
The idea was to drill through the ice sheet into the sea below and then drill into the sea floor below that. Scientists hoped to study sediments to learn about Antarcticclimate change over millions of years.
Until Andrill, scientists had drilled into the ice to study climate. But the ice sheets and shelves that cover Antarctica only go back only about 800,000 years. Drilling into the earth below the sea would provide cores dating far earlier than that.
The cores that were obtained are still being studied, and more drilling projects are taking place. Still, studies to date tell a fascinating story about Antarctica and climate change around the world.
Antarctica contains about 90 percent of the Earth’s ice according to an Andrill report. The total volume is estimated at 29 million cubic kilometers to 32 million cubic kilometers.
If all that ice should melt, sea levels could rise as much as 200 feet. For reference, that would cover nearly all of Philadelphia with water.
Andrill is a multi-national effort staffed by researchers from Germany, Italy, New Zealand, and the United States. Andrill scientists have learned that Antarctica was not always covered in ice, even during the recent ice age.
Some 190 million years ago, Antarctica was located closer to the Equator. Connected to present day Australia, India, and East Africa in the supercontinent Pangea, the climate was warm enough to support vegetation and animal life.
As Pangea broke up, Antarctica drifted south toward the South Pole. For the past 100 million years it has been roughly in its present position. That would seem to indicate that it was covered by ice during that entire time.
That is not the case. Several times the continent has warmed sufficiently to allow plant life to return. Volcanoes erupted, depositing fine ash on top of ice. And marine creatures associated with warm oceans were found in the sediments.
In other words, Antarctica warmed and cooled several times in the past 100 million years.
The present ice sheet did not begin to form until 34 million years ago. Then, during the Pliocene about 5 million years ago, the continent warmed up yet again.
Scientists have discovered remnants of peat moss, wood fragments, and leaves that were buried in sediments, but flash frozen. They never had a chance to become fossilized into coal. The fragments are the original plants.
In the Mullens Valley of East Antarctica, volcanic ash that settled on top of the ice sheet is pristine. The ice never melted and the ash never formed into rock. The ash is millions of years old and evidence that volcanic activity occurred about that time.
Evidence of the Pliocene warming is found around the Earth. In New Zealand, sediments include fossils of marine creatures, indicating the sea level was some 60 feet higher. Along the shores of the Chesapeake Bay, the same evidence is found.
This indicates that the Antarctic ice sheet has melted at least partially in the past 30 million years and will likely do so again.
These variations were natural cycles in Earth’s climate. Current concerns over global warming look to human burning of fossil fuels as a warming influence.
Next week: Meltdown
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