I.S.E.P. © All rights reserved 2009

WEATHER AND EARTHQUAKES

Q: Is there earthquake weather?

A: In the 4th Century B.C., Aristotle proposed that earthquakes were caused by winds trapped in subterranean caves. Small tremors were thought to have been caused by air pushing on the cavern roofs, and large ones by the air breaking the surface. This theory lead to a belief in earthquake weather, that because a large amount of air was trapped underground, the weather would be hot and calm before an earthquake. A later theory stated that earthquakes occurred in calm, cloudy conditions, and were usually preceded by strong winds, fireballs, and meteors.

USGS answers :

However, there is no connection between weather and earthquakes. They are the result of geologic processes within the earth and can happen in any weather and at any time during the year. Earthquakes originate miles underground. Wind, precipitation, temperature, and barometric pressure changes affect only the surface and shallow subsurface of the Earth. Earthquakes are focused at depths well out of the reach of weather, and the forces that cause earthquakes are much larger than the weather forces. Earthquakes occur in all types of weather, in all climate zones, in all seasons of the year, and at any time of day. Sometimes, we are asked: "Do earthquakes change the weather in any way? Earthquakes themselves do not cause weather to change. Earthquakes, however, are a part of global tectonics, a process that often changes the elevation of the land and its morphology. Tectonics can cause inland areas to become coastal or vice versa. Changes significant enough to alter the climate occur over millions of years.

FAR from being the benign figure of mythology, Mother Earth is short-tempered and volatile. So sensitive in fact, that even slight changes in weather and climate can rip the planet's crust apart, unleashing the furious might of volcanic eruptions, earthquakes and landslides.That's the conclusion of the researchers who got together last week in London at the conference on Climate Forcing of Geological and Geomorphological Hazards. It suggests climate change could tip the planet's delicate balance and unleash a host of geological disasters.

What's more, even our attempts to stall global warming could trigger a catastrophic event but only now is it becoming clear just how sensitive rock can be to the air, ice and water above. "You don't need huge changes to trigger responses from the crust," says Bill McGuire of University College London (UCL), who organised the meeting. "The changes can be tiny." You don't need huge changes to trigger a response from the crust.

They can be tiny. Among the various influences on the Earth's crust, from changes in weather to fluctuations in ice cover, the oceans are emerging as a particularly fine controller. Simon Day of the University of Oxford, McGuire and Serge Guillas, also at UCL, have shown how subtle changes in sea level may affect the seismicity of the East Pacific Rise, one of the fastest-spreading plate boundaries.

The researchers focused on the Easter microplate - the tectonic plate that lies beneath the ocean off the coast of Easter Island - because it is relatively isolated from other faults. This makes it easier to distinguish changes in the plate caused by climate systems from those triggered by regional rumbles. Since 1973, the arrival of El Niño every few years has correlated with a greater frequency of underwater quakes between magnitude 4 and 6.The team is confident that the two are linked. El Niño raises the local sea level by a few tens of centimetres, and they believe the extra water weight may increase the pressure of fluids in the pores of the rock beneath the seabed.

This might be enough to counteract the frictional force that holds the slabs of rock in place, making it easier for faults to slip. "The changes in sea level are tiny," says Day. "A small additional perturbation can have a substantial effect."Small ocean changes can also influence volcanic eruptions, says David Pyle of the University of Oxford. His study of eruptions over the past 300 years with Ben Mason of the University of Cambridge and colleagues reveals that volcanism varies with the seasons.

The team found that there are around 20 per cent more eruptions worldwide during the northern hemisphere's winter than the summer (Journal of Geophysical Research, DOI: 10.1029/2002JB002293). The reason may be that global sea level drops slightly during the northern hemisphere's winter. Because there is more land in the northern hemisphere, more water is locked up as ice and snow on land than during the southern hemisphere's winter.The vast majority of the world's most active volcanoes are within a few tens of kilometres of the coast (see map). This suggests the seasonal removal of some of the ocean's weight at continental margins as sea level drops could be triggering eruptions around the world, says Pyle.The suggestion that some volcanoes erupt when sea levels drop does not necessarily mean that sea levels rising under climate change will suppress volcanism.

In Alaska, Mount Pavlof erupts more often in the winter months, and previous research by Steve McNutt of the Alaska Volcano Observatory puts this down to a local sea level rise of 30 centimetres every winter due to low air pressure and high storm winds. Pavlof's location means that the extra weight of the adjacent sea could be squeezing magma towards the surface.In other regions, additional ocean weight at continental margins as sea levels rise could bend the crust, reducing compressional conditions, says McGuire. Magma may then find it easier to reach the surface at adjacent volcanoes.All these examples may seem contradictory, but the crucial point is that any change in sea level may alter regional stresses at continental margins enough to trigger eruptions in a volcano already primed to erupt, he says.Small changes in rainfall can also trigger volcanic eruptions.

In 2001, a major eruption of the Soufrière Hills volcano on the Caribbean island of Montserrat was set in motion by particularly heavy rainfall. This destabilised the volcano's dome enough for it to collapse and unleash magma within. Now it seems even typical tropical rain showers could trigger an eruption. And climate models suggest that many regions, including parts of the tropics, are likely to get wetter with climate change.Adrian Matthews of the University of East Anglia, UK, and colleagues measured the minute-by-minute response of Montserrat's volcano after more than 200 bouts of precipitation over three years. The team found that these events, which Matthews says were typical of tropical weather, were followed by two days of increased volcanic activity.A rainy day increased the likelihood of dome collapse from 1.5 per cent to 16 per cent. "It wouldn't have to be spectacularly heavy rainfall," says Matthews. "You don't have to have a hurricane." (Journal of Volcanology and Geothermal Research, DOI: 10.1016/j.jvolgeores.2009.05.010)

Perhaps the greatest geological hazards during climate change will be the result of melting ice sheets. Apart from the risk that loose sediments exposed by melted ice could slip into the sea as tsunami-generating landslides, the removal of heavy ice could also trigger volcanic eruptions. "Even thinning of a few tens of metres could make a difference," says Andrew Russell of the University of Newcastle in the UK.For example, Iceland's Vatnajökull ice cap sits over a plate boundary and several volcanoes. That ice is likely to disappear within the next two centuries. "If that happens you'll get rid of an awful lot of weight that will allow an increase in volcanic activity," says Russell. In the wake of the last ice age, volcanism was up to 30 times greater in northern Iceland compared with today (Earth Surface Processes and Landforms, DOI: 10.1002/esp.1811).

Icy eruptions could reverberate round the world. In 1783, the Icelandic volcano Laki sent a sulphurous smog over Europe, plunging it into an extreme winter that killed thousands.For now, it is unclear just how much climate change will affect the frequency and intensity of quakes and eruptions, says McGuire, because Earth's sensitivity to climate is only now emerging. There is not yet enough data to build predictive climate models linking the two systems. But it's crucial that we consider just how easily our actions could provoke the planet, he argues. "It's serious science, not scaremongering."

Bury the carbon, set off a quake?It all looked so promising - tidy carbon dioxide away underground and forget about it. But even as the US's first large-scale sequestration operation is getting off the ground at the Mountaineer plant in West Virginia, geophysicists are concerned that burying the carbon could trigger earthquakes and tsunamis.In a carbon sequestration power plant (CCS), CO2 is extracted from the exhaust then pumped into aquifers and old gas fields several kilometres beneath the Earth's surface. So far so good. But the CO2 expands as it rises through the porous rock, increasing pressure inside.

"As CO2 is injected into an aquifer it may induce microseismicity. However, CCS operations carried out in line with the recently published European Union regulatory guidelines would not pose an earthquake risk," says Andrew Chadwick of the British Geological Survey.Chemical reactions between the injected CO2, water and rock could also destabilise the rock, says Ernest Majer, a seismologist at the Lawrence Berkeley National Laboratory in California who briefed the Senate on CCS hazards this week. "It's such a new technology that none of these issues have been addressed," says Majer.

 

Shanta Barley

Climate Change IS Increasing the Frequencies of Major Geological Events There will be more earthquakes, volcanic eruptions and landslides both on the land and sea floorIn a study first published on the web in 2004, NASA and United States Geological Survey (USGS) scientists found that retreating glaciers in southern Alaska may lead to more earthquakes in future.“The study examined the likelihood of increased earthquake activity in southern Alaska as a result of rapidly melting glaciers. As glaciers melt they lighten the load on the Earth’s crust.

Tectonic plates, that are mobile pieces of the Earth’s crust, can then move more freely.” [The study appeared in the July 2004 issue of the Journal of Global and Planetary Change.Jeanne Sauber of NASA's Goddard Space Flight Center and Bruce Molnia, a research geologist at USGS used NASA satellite and global positioning instruments, together with computer models, to analyze tectonic plates movements in relation to melting glaciers in Alaska."Historically, when big ice masses started to retreat, the number of earthquakes increased," Sauber said.

"More than 10,000 years ago, at the end of the great ice age, big earthquakes occurred in Scandinavia as the large glaciers began to melt. In Canada, many more moderate earthquakes occurred as ice sheets melted there," she added."Southern Alaskan glaciers are very sensitive to climate change, Sauber added. Many glaciers have shrunk or disappeared over the last 100 years. The trend, which appears to be accelerating, seems to be caused by higher temperatures and changes in precipitation." the report said.

They discovered that a tectonic plate under the Pacific Ocean in southern Alaska was pushing toward the coast, creating very steep mountains. "The high mountains and heavy precipitation are critical for glacier formation. The colliding plates create a great deal of pressure that builds up, and eventually is relieved by earthquakes."The sheer weight of massive glaciers that rest atop active seismic areas help minimize plate tectonic movements. "But, as the glaciers melt and their load on the plate lessens, there is a greater likelihood of an earthquake happening to relieve the large strain underneath.

"Major earthquakes occur as a result of plate tectonic movements.

The researchers believe that a 1979 earthquake in southern Alaska, dubbed the St. Elias earthquake, which  measured 7.2 on the Richter scale, occurred  because the local glaciers melted."Along the fault zone, in the region of the St. Elias earthquake, pressure from the Pacific plate sliding under the continental plate had built up since 1899 when previous earthquakes occurred. Between 1899 and 1979, many glaciers near the fault zone thinned by hundreds of meters and some completely disappeared. Photographs of these glaciers, many taken by Molnia during the last 30 years, were used to identify details within areas of greatest ice loss.

"Field measurements were also used to determine how much the glacier's ice thickness changed since the late 19th century. The researchers estimated the volume of ice that melted and then calculated how much instability the loss of ice may have caused. They found the loss of ice would have been enough to stimulate the 1979 earthquake.The two scientists, Sauber and Molnia used data from global positioning system and NASA satellites as well as Shuttle Radar Topography Mission (SRTM) to document the glacier extent and topography."In the future, in areas like Alaska where earthquakes occur and glaciers are changing, their relationship must be considered to better assess earthquake hazard, and our satellite assets are allowing us to do this by tracking the changes in extent and volume of the ice, and movement of the Earth," Sauber said.

Source"Climate change: Tearing the Earth apart?"Bill McGuire, professor of Geophysical Hazards at University College, in an article in New Scientist, titled "Climate change: Tearing the Earth apart?" wrote:"In the early 1970s John Chappell of the Australian National University in Canberra was the first to make the link between glacial advances and retreats and the rate of global volcanism. We now know that the warming that heralded the start of the current interglacial period around 10,000 years ago brought forth a burst of volcanic activity in Iceland, as melting ice caps reduced pressures on the magma chambers below.

Allen Glazner of the University of North Carolina at Chapel Hill identified a similar pattern in eastern California over the past 800,000 years. Increased levels of volcanic activity are also recorded at mid-latitude ice-covered volcanoes in the Cascades Range of the US and in the Andes.""[I]t shouldn’t come as a surprise that the loading and unloading of the Earth’s crust by ice or water can trigger seismic and volcanic activity and even landslides. Dumping the weight of a kilometre-thick ice sheet onto a continent or removing a deep column of water from the ocean floor will inevitably affect the stresses and strains on the underlying rock.” McGuire said.“Not every volcanic eruption and earthquake in the years to come will have a climate-change link… 

Yet as the century progresses we should not be surprised by more geological disasters as a direct and indirect result of dramatic changes to our environment. The only saving grace is that a significant increase in volcanic activity would pump large volumes of sulphate gases into the stratosphere, which would cool the Earth’s surface and slow global warming, at least for a time. It’s a hell of a price to pay, though, for ignoring a phenomenon that could be far more easily sorted if we lived more considered and sustainable lives.” He said.

FEWW Team believes that aerial bombardment, nuclear tests, large scale urbanization, use of explosive for mining and similar activities, as well as human mobility also play  significant roles in increasing the frequencies of earthquakes, volcanic eruptions and land and sea-floor landslides.