How did dinosaurs disappear? |
 | |  | |  |
How did dinosaurs disappear?
[1] Asteroid
A single, gigantic asteroid slammed into Earth 65 million years ago,
wipping out dinosaurs and many other species. The asteroid plunged
into Mexico's Yucatan Peninsula to carve out the Chicxulub crater. The
impact triggered a worldwide environmental catastrophe expelling vast
quantities of rock and dust into the sky, unleashing giant tsunamis,
sparking global wildfires and leaving Earth shrouded in darkness for
years. [3,4]
Professor Ken MacLeod at University of Missouri-Columbia found
evidence for this notion by examining the rock sediments drilled from
five sites at the bottom of the Atlantic Ocean. [3,4]
[2] Volcanic Eruptions
The dinosaurs died gradually from climate change caused by a series
of severe volcanic eruptions in India at the end of the Cretaceous
period, says Gerta Keller, professor of geosciences at Princeton
University. However, Keller's theory has not yet been adopted by the
broader scientific community. The most significant finding is geologic
evidence that the mass extinction and the impact of the giant meteor
occurred at two different times.
"The Chicxulub impact hit the Yucatan about 300,000 years before the
mass extinction that included the dinosaurs and therefore could not
have caused it," Keller says. "We know the age of impact because my
team discovered a layer of tiny glass melt-rock spherules in Mexico and
Texas." The spherules formed when the rocks were vaporized by the
impact and blown into the stratosphere--and then rained down over
North and Central America. "This glass spherule layer marks the
precise time of the impact 300,000 years ago," she notes.
The sediments and fossils in the older sediments below the spherule
layer and younger sediments above it reveal how life was affected by
the impact.
"We see no change, not a single species died out, so the mass
extinction 300,000 years later must have been caused by another
catastrophe," Keller says. She's firm in her belief that the other
catastrophe was a series of volcanic eruptions in the Deccan Traps, a
volcanic mountain range that covers much of India today. The
mountains, which today are 12,000 feet high, were much higher in
prehistoric times.
"Volcanic eruptions poured out lava flows after lava flows, stacking
them like a layer cake," she says. "The total volume in cubic miles was
greater than the Rockies and the Sierras combined."
Related research by volcanologists Vincent Courtillot, Steve Self, Mike
Widdowson, and Anne Lise Chenet shows the lava eruptions were not
continuous but occurred in pulses, with each pulse lasting about 10--to
at most 100--years, and the pulses were separated by short time
periods of quiescence. New results from eight subsurface cores drilled
by the Oil and Gas Corporation of India in the Krishna-Godavari Basin
of eastern India reveal that at least nine lava flows mark the critical
volcanic phase that ended in the mass extinction. This ending phase
may have occurred over as little as 10,000 to 100,000 years. For each
lava eruption, fire shot in tall columns from fissures in the Earth's
surface and lofted gases into the stratosphere while the oozing lava
spread sheet-like, or in rivers, up to 650 miles across India, and
formed the longest lava flows on Earth.
"Their destructive nature is evident in the marine life record, which
decreased by about 50 percent after the first of these long lava flows,"
Keller said. "By the time of the last lava flow, the mass extinction was
complete."
The sulfur dioxide gas injected into the stratosphere converted to
sulfate aerosols that caused climate cooling. The cooling lasted until
the sulfate aerosols washed out as acid rain and caused the ocean to
acidify in the process.
Research on smaller and more recent eruptions, such as the Laki
eruption of Iceland in 1783-1784, clarified for scientists the extreme
climate effects of volcanic eruptions and the resulting death and
destruction of humans, animals, plants and marine life. In spite of the
widespread devastation caused by Laki, mass extinction did not occur.
The more recent example of Mt. St. Helen's in Washington State has
shown just how quickly a local ecosystem can come back after a
volcanic eruption.
Then why did it take Earth's ecosystem half a million years to fully recover
after the mass extinction that killed the dinosaurs?
"The answer seems to be the occurrence of at least four additional
massive Deccan eruptions about 280,000 years after the mass
extinction," Keller says. "After those final eruptions, Earth began a full
recovery leading to the evolution of life as we know it."
Keller doesn't disagree with scientists who believe the Chicxulub
impact affected climate. The event would certainly have caused
earthquakes, tsunamis, regional fires and injected huge quantities of
sulfur dioxide into the stratosphere, causing cooling and acidification of
the land and oceans. "The difference is that the quantity of gas injection
from the main phase of Deccan eruptions was 30 to 100 times larger than
the Chicxulub impact and occurred over as little as 10,000 to 100,000
years, with each pulse lasting about 10 years or more."
Up until now, skeptics have doubted whether gas from Deccan-like
eruptions reaches the stratosphere, but the relatively small 1783-1784
Laki eruption in Iceland revealed that even rather small eruptions loft
gases into the stratosphere.
Until recently, it was also believed that the last phase of Deccan
volcanic eruptions occurred over a million-year period, which would
have been long enough for the environment to recover between
eruptions, thus preventing a runaway extinction effect. Vincent
Courtillot and collaborators from the Institut de Physique du Globe de
Paris have recently discovered that the main phase of Deccan
eruptions was much shorter and culminated near the
Cretaceous-Tertiary boundary. Known as the "K-T boundary" to
scientists, it marks the end of the Mesozoic Era and is associated with
the mass extinction.
Most importantly, field work by Keller and her collaborators revealed
that the mass extinction coincided with the end of the main phase of
Deccan eruptions suggesting that volcanism is the "smoking gun" that
killed the dinosaurs.
Reference
Volcanoes, Not Asteroid, May Have Taken Out the Dinosaurs
The National Science Foundation October 2009
[1] Tiny ancestor is T. rex blueprint BBC Thursday, 17 September 2009
[2] Unveiled: The Surprisingly Small Precursor of T. Rex The Washington Post,
September 17, 2009
[3] Single massive asteroid wiped out dinosaurs: study Reuters Nov 30, 2006
[4] Study: Single Meteorite Impact Killed Dinosaurs LiveScience.com Nov 28,
2006
All Rights Reserved.
[1] Asteroid
A single, gigantic asteroid slammed into Earth 65 million years ago,
wipping out dinosaurs and many other species. The asteroid plunged
into Mexico's Yucatan Peninsula to carve out the Chicxulub crater. The
impact triggered a worldwide environmental catastrophe expelling vast
quantities of rock and dust into the sky, unleashing giant tsunamis,
sparking global wildfires and leaving Earth shrouded in darkness for
years. [3,4]
Professor Ken MacLeod at University of Missouri-Columbia found
evidence for this notion by examining the rock sediments drilled from
five sites at the bottom of the Atlantic Ocean. [3,4]
[2] Volcanic Eruptions
The dinosaurs died gradually from climate change caused by a series
of severe volcanic eruptions in India at the end of the Cretaceous
period, says Gerta Keller, professor of geosciences at Princeton
University. However, Keller's theory has not yet been adopted by the
broader scientific community. The most significant finding is geologic
evidence that the mass extinction and the impact of the giant meteor
occurred at two different times.
"The Chicxulub impact hit the Yucatan about 300,000 years before the
mass extinction that included the dinosaurs and therefore could not
have caused it," Keller says. "We know the age of impact because my
team discovered a layer of tiny glass melt-rock spherules in Mexico and
Texas." The spherules formed when the rocks were vaporized by the
impact and blown into the stratosphere--and then rained down over
North and Central America. "This glass spherule layer marks the
precise time of the impact 300,000 years ago," she notes.
The sediments and fossils in the older sediments below the spherule
layer and younger sediments above it reveal how life was affected by
the impact.
"We see no change, not a single species died out, so the mass
extinction 300,000 years later must have been caused by another
catastrophe," Keller says. She's firm in her belief that the other
catastrophe was a series of volcanic eruptions in the Deccan Traps, a
volcanic mountain range that covers much of India today. The
mountains, which today are 12,000 feet high, were much higher in
prehistoric times.
"Volcanic eruptions poured out lava flows after lava flows, stacking
them like a layer cake," she says. "The total volume in cubic miles was
greater than the Rockies and the Sierras combined."
Related research by volcanologists Vincent Courtillot, Steve Self, Mike
Widdowson, and Anne Lise Chenet shows the lava eruptions were not
continuous but occurred in pulses, with each pulse lasting about 10--to
at most 100--years, and the pulses were separated by short time
periods of quiescence. New results from eight subsurface cores drilled
by the Oil and Gas Corporation of India in the Krishna-Godavari Basin
of eastern India reveal that at least nine lava flows mark the critical
volcanic phase that ended in the mass extinction. This ending phase
may have occurred over as little as 10,000 to 100,000 years. For each
lava eruption, fire shot in tall columns from fissures in the Earth's
surface and lofted gases into the stratosphere while the oozing lava
spread sheet-like, or in rivers, up to 650 miles across India, and
formed the longest lava flows on Earth.
"Their destructive nature is evident in the marine life record, which
decreased by about 50 percent after the first of these long lava flows,"
Keller said. "By the time of the last lava flow, the mass extinction was
complete."
The sulfur dioxide gas injected into the stratosphere converted to
sulfate aerosols that caused climate cooling. The cooling lasted until
the sulfate aerosols washed out as acid rain and caused the ocean to
acidify in the process.
Research on smaller and more recent eruptions, such as the Laki
eruption of Iceland in 1783-1784, clarified for scientists the extreme
climate effects of volcanic eruptions and the resulting death and
destruction of humans, animals, plants and marine life. In spite of the
widespread devastation caused by Laki, mass extinction did not occur.
The more recent example of Mt. St. Helen's in Washington State has
shown just how quickly a local ecosystem can come back after a
volcanic eruption.
Then why did it take Earth's ecosystem half a million years to fully recover
after the mass extinction that killed the dinosaurs?
"The answer seems to be the occurrence of at least four additional
massive Deccan eruptions about 280,000 years after the mass
extinction," Keller says. "After those final eruptions, Earth began a full
recovery leading to the evolution of life as we know it."
Keller doesn't disagree with scientists who believe the Chicxulub
impact affected climate. The event would certainly have caused
earthquakes, tsunamis, regional fires and injected huge quantities of
sulfur dioxide into the stratosphere, causing cooling and acidification of
the land and oceans. "The difference is that the quantity of gas injection
from the main phase of Deccan eruptions was 30 to 100 times larger than
the Chicxulub impact and occurred over as little as 10,000 to 100,000
years, with each pulse lasting about 10 years or more."
Up until now, skeptics have doubted whether gas from Deccan-like
eruptions reaches the stratosphere, but the relatively small 1783-1784
Laki eruption in Iceland revealed that even rather small eruptions loft
gases into the stratosphere.
Until recently, it was also believed that the last phase of Deccan
volcanic eruptions occurred over a million-year period, which would
have been long enough for the environment to recover between
eruptions, thus preventing a runaway extinction effect. Vincent
Courtillot and collaborators from the Institut de Physique du Globe de
Paris have recently discovered that the main phase of Deccan
eruptions was much shorter and culminated near the
Cretaceous-Tertiary boundary. Known as the "K-T boundary" to
scientists, it marks the end of the Mesozoic Era and is associated with
the mass extinction.
Most importantly, field work by Keller and her collaborators revealed
that the mass extinction coincided with the end of the main phase of
Deccan eruptions suggesting that volcanism is the "smoking gun" that
killed the dinosaurs.
Reference
Volcanoes, Not Asteroid, May Have Taken Out the Dinosaurs
The National Science Foundation October 2009
[1] Tiny ancestor is T. rex blueprint BBC Thursday, 17 September 2009
[2] Unveiled: The Surprisingly Small Precursor of T. Rex The Washington Post,
September 17, 2009
[3] Single massive asteroid wiped out dinosaurs: study Reuters Nov 30, 2006
[4] Study: Single Meteorite Impact Killed Dinosaurs LiveScience.com Nov 28,
2006
All Rights Reserved.
Earth
Energy
Electricity
Solar Energy
Nature Gas
Dinosaurs
Evolution
Harvest Moon
Permafrost
The Missing Link-
Adri
Energy
Electricity
Solar Energy
Nature Gas
Dinosaurs
Evolution
Harvest Moon
Permafrost
The Missing Link-
Adri
| Did jumbo dinosaurs have budget-sized versions? Raptorex kriegsteini, would have weighed around 65kg (150 pounds); its descendants were 90 times as massive (13,000 pounds). The 125-million-year-old animal suggests that T. rex's characteristic big head with enhanced jaw, relatively small forearms and huge back legs were inherited from this much smaller dinosaur, and that the body type changed little over millions of years except in size. These previous finds have confirmed that the Tyrannosaur family of dinosaurs is descended from small-bodied, long-armed predecessors. [1] The discovery of the Raptorex, a tiny precursor to the gigantic Tyrannosaurus rex, raises the question of whether other jumbo dinosaurs had budget-sized versions. [2] |