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Eruptions spark explosions of life.



Despite their reputation as deadly scourges, giant volcanic eruptions volcanic eruptions

discharging of fumes, dust and lava from volcanoes. They have damaging potential in addition to those of being physically overpowering by the lava flow or the ash or dust fallout.
 may have profoundly benefited life on Earth by triggering two of the greatest biological revolutions in the planet's history.

Massive outpourings of lava, particularly those in the deep ocean, spurred bursts of evolution early in the Paleozoic era, about 550 million years ago, and in the middle of the Mesozoic era, around 200 million years ago, claims biologist Geerat J. Vermeij Dr. Geerat J. Vermeij is a professor of geology at the University of California at Davis. Blind from the age of six, he graduated from Princeton University in 1968 and received his Ph.D. in biology and geology from Yale University in 1971.  of the University of California, Davis The University of California, Davis, commonly known as UC Davis, is one of the ten campuses of the University of California, and was established as the University Farm in 1905. . In support of this controversial hypothesis, Vermeij notes that the biological changes took place while extensive undersea eruptions were creating new ocean basins and ripping apart oversized o·ver·size  
n.
1. A size that is larger than usual.

2. An oversize article or object.

adj. o·ver·size also o·ver·sized
Larger in size than usual or necessary.
 continents.

"We have simply got to explain the timing, and to me the coincidence between some of these huge volcanic events and the biological revolutions is just too weird. There has to be a connection," Vermeij told Science News.

The early Paleozoic revolution produced the first predators, burrowing animals, and creatures able to harvest minerals to form skeletons. Starting in late Precambrian time, this biological blast extended into the middle Ordovician period. The Mesozoic revolution ran from the late Triassic period through the late Cretaceous. It brought a proliferation of marine creatures, including important new types of plankton plankton: see marine biology.
plankton

Marine and freshwater organisms that, because they are unable to move or are too small or too weak to swim against water currents, exist in a drifting, floating state.
 that could grow mineralized min·er·al·ize  
v. min·er·al·ized, min·er·al·iz·ing, min·er·al·iz·es

v.tr.
1. To convert to a mineral substance; petrify.

2. To transform a metal into a mineral by oxidation.

3.
 shells. On land, social insects and flowering plants began to conquer the continents.

To explain the coincidence between geologic and biological events, Vermeij suggests that the submarine eruptions loosened the restrictions on organisms living at the time by increasing the availability of energy and nutrients. Using economics as an analogy, he suggests that the volcanic eruptions enhanced the supply of raw materials in the environment and provided organisms with easier access to such commodities. Vermeij discussed his hypothesis last month in the spring issue of Paleobiology pa·le·o·bi·ol·o·gy  
n.
The branch of paleontology that deals with the fossils of plants, animals, and other organisms.



pa
.

Undersea eruptions aided life on Earth by releasing massive amounts of carbon dioxide carbon dioxide, chemical compound, CO2, a colorless, odorless, tasteless gas that is about one and one-half times as dense as air under ordinary conditions of temperature and pressure. , which produced periods of greenhouse warming, claims Vermeij. In the warmer climates, biologically important chemical reactions could proceed much more readily, enabling organisms to boost their metabolisms. Warmer weather and increased amounts of carbon dioxide in the atmosphere also enhanced erosion on the continents, thereby freeing important nutrients from rocks.

The volcanic activity altered the landscape as well. Eruptions raised sea levels by producing hot new ocean crust that sat higher than the old ocean floor. As the swollen oceans flooded continental coastlines, the area of shallow seas grew markedly. These regions, with their abundant nutrients and sunlit waters, would have provided fertile new habitats for ocean organisms.

The question of what sparks biological revolutions has long captivated cap·ti·vate  
tr.v. cap·ti·vat·ed, cap·ti·vat·ing, cap·ti·vates
1. To attract and hold by charm, beauty, or excellence. See Synonyms at charm.

2. Archaic To capture.
 paleontologists and evolutionary theorists. Some researchers have favored so-called intrinsic explanations, which link evolutionary bursts to genetic or biochemical innovations such as the origin of seed-bearing plants. Other scientists tie life revolutions to external causes, such as chemical changes in the ocean, climate changes, or mass extinctions.

In Vermeij's theory, external factors explain only part of the story. Ecological forces, such as competition and predation predation

Form of food getting in which one animal, the predator, eats an animal of another species, the prey, immediately after killing it or, in some cases, while it is still alive. Most predators are generalists; they eat a variety of prey species.
 among organisms, also play an important role in evolution. "The timing and rates of evolution are dictated by extrinsic factors, but the directions of evolution are largely determined by what other organisms are doing," he says.

David Jablonski of the University of Chicago says that Vermeij offers a number of tests for assessing the new hypothesis. He cautions, however, that paleontologists always face a difficult task when trying to document whether one event caused another.

Paleontologist Douglas Erwin of the National Museum of Natural History For the museum in Manhattan, see .

This article is about the museum in Washington, D.C.. For other uses, see National Museum of Natural History (disambiguation).

The National Museum of Natural History
 in Washington, D.C., questions the link between volcanic eruptions and biological revolutions. "I don't think the timing [of the two] is really as close as it would need to be," says Erwin.

But he lauds Vermeij for bringing economic arguments to evolutionary studies. Although scientists since Darwin have linked the two subjects, Vermeij has done so more completely than others. "I think economics are enormously fruitful and tremendously underutilized," says Erwin. "I've told students that the two courses they should take outside paleontology paleontology (pā'lēəntŏl`əjē) [Gr.,= study of early beings], science of the life of past geologic periods based on fossil remains.  are Shakespeare and economics."
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Title Annotation:how volcanoes helped life develop
Author:Monastersky, Richard
Publication:Science News
Date:Jul 1, 1995
Words:660
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