Font ResizeCalifornia drought: Past dry periods have lasted more than 200 years, scientists say
California's current drought is being billed as the driest period in the state's recorded rainfall history. But scientists who study the West's long-term climate patterns say the state has been parched for much longer stretches before that 163-year historical period began.And they worry that the "megadroughts" typical of California's earlier history could come again.Through studies of tree rings, sediment and other natural evidence, researchers have documented multiple droughts in California that lasted 10 or 20 years in a row during the past 1,000 years -- compared to the mere three-year duration of the current dry spell. The two most severe megadroughts make the Dust Bowl of the 1930s look tame: a 240-year-long drought that started in 850 and, 50 years after the conclusion of that one, another that stretched at least 180 years.
"We continue to run California as if the longest drought we are ever going to encounter is about seven years," said Scott Stine, a professor of geography and environmental studies at Cal State East Bay. "We're living in a dream world."California in 2013 received less rain than in any year since it became a state in 1850. And at least one Bay Area scientist says that based on tree ring data, the current rainfall season is on pace to be the driest since 1580 -- more than 150 years before George Washington was born. The question is: How much longer will it last?A megadrought today would have catastrophic effects.California, the nation's most populous state with 38 million residents, has built a massive economy, Silicon Valley, Hollywood and millions of acres of farmland, all in a semiarid area. The state's dams, canals and reservoirs have never been tested by the kind of prolonged drought that experts say will almost certainly occur again.Stine, who has spent decades studying tree stumps in Mono Lake, Tenaya Lake, the Walker River and other parts of the Sierra Nevada, said that the past century has been among the wettest of the last 7,000 years.
The low water level reveals two chairs at the Almaden Reservoir in San Jose, Calif., on Wednesday, Jan. 22, 2014.
(Nhat V. Meyer)Looking back, the long-term record also shows some staggeringly wet periods. The decades between the two medieval megadroughts, for example, delivered years of above-normal rainfall -- the kind that would cause devastating floods today.The longest droughts of the 20th century, what Californians think of as severe, occurred from 1987 to 1992 and from 1928 to 1934. Both, Stine said, are minor compared to the ancient droughts of 850 to 1090 and 1140 to 1320.Modern megadroughtWhat would happen if the current drought continued for another 10 years or more?Without question, longtime water experts say, farmers would bear the brunt. Cities would suffer but adapt.The reason: Although many Californians think that population growth is the main driver of water demand statewide, it actually is agriculture. In an average year, farmers use 80 percent of the water consumed by people and businesses -- 34 million of 43 million acre-feet diverted from rivers, lakes and groundwater, according to the state Department of Water Resources."Cities would be inconvenienced greatly and suffer some. Smaller cities would get it worse, but farmers would take the biggest hit," said Maurice Roos, the department's chief hydrologist. "Cities can always afford to spend a lot of money to buy what water is left."Roos, who has worked at the department since 1957, said the prospect of megadroughts is another reason to build more storage -- both underground and in reservoirs -- to catch rain in wet years.In a megadrought, there would be much less water in the Delta to pump. Farmers' allotments would shrink to nothing. Large reservoirs like Shasta, Oroville and San Luis would eventually go dry after five or more years of little or no rain.Farmers would fallow millions of acres, letting row crops die first. They'd pump massive amounts of groundwater to keep orchards alive, but eventually those wells would go dry. And although deeper wells could be dug, the costs could exceed the value of their crops. Banks would refuse to loan the farmers money.The federal government would almost certainly provide billions of dollars in emergency aid to farm communities."Some small towns in the Central Valley would really suffer. They would basically go away," said Jay Lund, a professor of civil and environmental engineering at UC Davis."But agriculture is only 3 percent of California's economy today," Lund said. "In the main urban economy, most people would learn to live with less water. It would be expensive and inconvenient, but we'd do it."Farmers with senior water rights would make a huge profit, he noted, selling water at sky-high prices to cities. Food costs would rise, but there wouldn't be shortages, Lund said, because Californians already buy lots of food from other states and countries and would buy even more from them. In urban areas, most cities would eventually see water rationing at 50 percent of current levels. Golf courses would shut down. Cities would pass laws banning watering or installing lawns, which use half of most homes' water. Across the state, rivers and streams would dry up, wiping out salmon runs. Cities would race to build new water supply projects, similar to the $50 million wastewater recycling plant that the Santa Clara Valley Water District is now constructing in Alviso.If a drought lasted decades, the state could always build dozens of desalination plants, which would cost billions of dollars, said law professor Barton "Buzz" Thompson, co-director of Stanford University's Woods Institute for the Environment.Saudi Arabia, Israel and other Middle Eastern countries depend on desalination, but water from desal plants costs roughly five times more than urban Californians pay for water now. Thompson said that makes desal projects unfeasible for most of the state now, especially when other options like recycled wastewater and conservation can provide more water at a much lower cost.But in an emergency, price becomes no object. "In theory, cities cannot run out of water," Thompson said. "All we can do is run out of cheap water, or not have as much water as we need when we really want it."Over the past 10 years, he noted, Australia has been coping with a severe drought. Urban residents there cut their water demand massively, built new supply projects and survived."I don't think we'll ever get to a point here where you turn on the tap and air comes out," he said.Some scientists believe we are already in a megadrought, although that view is not universally accepted.Bill Patzert, a research scientist and oceanographer at NASA's Jet Propulsion Laboratory in Pasadena, says that the West is in a 20-year drought that began in 2000. He cites the fact that a phenomenon known as a "negative Pacific decadal oscillation" is underway -- and that historically has been linked to extreme high-pressure ridges that block storms.Such events, which cause pools of warm water in the North Pacific Ocean and cool water along the California coast, are not the result of global warming, Patzert said. But climate change caused by the burning of fossil fuels has been linked to longer heat waves. That wild card wasn't around years ago."Long before the Industrial Revolution, we were vulnerable to long extended periods of drought. And now we have another experiment with all this CO2 in the atmosphere where there are potentially even more wild swings in there," said Graham Kent, a University of Nevada geophysicist who has studied submerged ancient trees in Fallen Leaf Lake near Lake Tahoe.Already, the 2013-14 rainfall season is shaping up to be the driest in 434 years, based on tree ring data, according to Lynn Ingram, a paleoclimatologist at UC Berkeley."It's important to be aware of what the climate is capable of," she said, "so that we can prepare for it."&&
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)The solo show 'Satchmo' by Terry Teachout depicts jazz legend Louis Armstrong reflecting on his bitter it plays at American Conservatory Theater through Feb. 7&(Photo by Charles Sykes/Invision/AP, File)George Lucas’ museum of American art and movie memorabila won’t be built in Chicago after all, after a parks group files suit.&Be who you needed when you were younger. by mercury_child | We Heart It
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This site has been recently redesigned. Please update your links to point to the new page located at
You will be redirected in 10 seconds to the new page location.Mercury - Educational facts and history of the planet Mercury.
Mercury is the closest planet to the .
Mercury is slightly smaller in diameter than the moons
but more than twice as massive.
Planet Profile
: 57,910,000 km (0.38 ) from Sun
: 4,880 km
: 3.30e23 kg
History of Mercury
In Roman mythology
is the god of commerce, travel and thievery, the
Roman counterpart of the Greek god
the messenger of the Gods.
The planet
probably received this name because it moves so quickly across the sky.
Mercury has been known since at least the time of the Sumerians (3rd millennium
It was sometimes given separate names for its apparitions as a
morning star and as an evening star.
Greek astronomers knew, however,
that the two names referred to the same body.
Heraclitus even believed that Mercury and Venus orbit the Sun, not the Earth.
Since it is closer to the Sun than the Earth, the illumination of Mercury's disk varies when viewed with a telescope from our perspective.
's telescope was too small to see Mercury's phases but he did see the phases of .
Mercury has been now been visited by two spacecraft,
Marriner 10 flew by three times in 1974 and 1975.
Only 45% of the surface
was mapped (and, unfortunately, it is too close to the Sun to be safely imaged
was launched by
NASA in 2004 and has been in orbit Mercury since 2011. Its first flyby in Jan
2008 provided new high quality images of some of the terrain not seen by Mariner
10. Since then Messenger has taken over 250,000 photographs coving the entire
planet. .The mission has provided support for the hypothesis that water
ice and other volatiles do exist in the polar regions in permanent shadow.
The hypothesis is supported by three independent lines of evidence:
1. MESSENGER’s Neutron Spectrometer made the first measurements of excess
hydrogen at the planet’s north pole.
2. Messenger’s Mercury Laser Altimeter (MLA) measured the reflectance of
Mercury’s polar deposits, and
3. The MLA has measured the topography of the polar regions enabling the first
detailed models of the surface and near-surface temperatures of Mercury’s north
polar regions utilizing the actual topography
it is only 46 million km from
the Sun but at
it is 70 million.
The position of the perihelion
processes around the Sun at a very slow rate.
19th century astronomers made very careful observations of Mercury's orbital
parameters but could not adequately explain them using
mechanics. The tiny differences
between the observed and predicted values were a minor but nagging
problem for many decades.
It was thought that another planet (sometimes called
slightly closer to the Sun than Mercury might
account for the discrepancy.
But despite much effort, no such
planet was found.
The real answer turned out to be much more dramatic:
Its correct prediction of the motions of Mercury was an important
factor in the early acceptance of the theory.
Until 1962 it was thought that Mercury's "day" was the same length as its "year"
so as to keep that same face to the Sun much as the Moon
does to the Earth. But this was shown to be false in 1965 by doppler
radar observations.
It is now known that Mercury rotates three times in two of
its years.
Mercury is the only body in the solar system known to have an
orbital/rotational
with a ratio other than 1:1 (though many have no resonances at all).
This fact and the high eccentricity of Mercury's orbit would produce
very strange effects for an observer on Mercury's surface.
At some longitudes the observer would see the Sun rise and then gradually
increase in apparent size as it slowly moved toward the zenith. At that point
the Sun would stop, briefly reverse course, and stop again before resuming its
path toward the horizon and decreasing in apparent size.
All the while the stars would be moving three times
faster across the sky.
Observers at other points on Mercury's surface would
see different but equally bizarre motions.
Temperature variations on Mercury are the most extreme in the solar system
ranging from 90 K to 700 K.
The temperature on
is slightly hotter but very stable.
Mercury craters
Mercury is in many ways similar to the :
its surface is heavily cratered and very
On the other hand, Mercury is much denser than the Moon (5.43 gm/cm3 vs 3.34).
Mercury is the second
major body in the
solar system, after . Actually Earth's density is
due in part to gravi if not for this, Mercury would be
denser than Earth.
This indicates that Mercury's dense iron core is
relatively larger than Earth's, probably comprising
the majority of the planet.
Mercury therefore has only a relatively thin
mantle and crust.
Mercury's interior is dominated by a large iron core whose radius is 1800 to 1900
The silicate outer shell (analogous to Earth's mantle and crust)
is only 500 to 600 km thick.
At least some of the core is probably molten.
Measurements from the Messenger spacecraft show Mercury’s magnetic field is
approximately three times stronger in the northern hemisphere than the southern
hemisphere and has led to breakthrough research. Modeling by Hao Cao, a UCLA
postdoctoral scholar working in the lab of Christopher Russell after considering
many factors, including how fast Mercury rotates and the chemistry and complex
motion of fluid inside the planet show the magnetic field of Mercury works
differently than it does on Earth.
Inside Earth's core, iron turns from a liquid to a solid at the inner boundary
of the planet's liquid outer core and the solid inner core is growing, and this
growth provides the energy that generates Earth's magnetic field. Inside
Mercury’s core, iron turns from a liquid to a solid at the outer boundary and
lacks a solid central core. Christopher Russell describes the mechanism: &It's
like a snow storm in which the snow formed at the top of the cloud and middle of
the cloud and the bottom of the cloud too&. &Our study of Mercury's magnetic
field indicates iron is snowing throughout this fluid that is powering Mercury's
magnetic field.&
According to Hao the cores of both Mercury and Earth contain light elements such
as sulfur, the presence of these light elements keeps the
cores from being completely solid and &powers the active magnetic
field-generation processes. The research currently appears online in the journal Geophysical Research
Letters and will be published in an upcoming print edition.
Mercury actually has a very thin atmosphere
consisting of atoms blasted off its surface by the
Because Mercury is so hot, these atoms
quickly escape into space.
Thus in contrast to the Earth and Venus whose atmospheres
are stable, Mercury's atmosphere is constantly being replenished.
Southwest Mercury
The surface of Mercury exhibits enormous escarpments, some up to hundreds of
kilometers in length and as much as three kilometers high.
Some cut thru the rings
of craters and other features in such a way as to indicate that they were formed
by compression.
It is estimated that the surface area of Mercury shrank by about
0.1% (or a decrease of about 1 km in the planet's radius).
Caloris Basin
One of the largest features on Mercury's surface is the Caloris Basin (right);
it is about 1300 km in diameter.
It is thought to be similar to the large
basins (maria) on the . Like the lunar basins, it
was probably caused by a very large
impact early in the history of the solar system.
Weird terrain opposite Caloris Basin
That impact was probably also responsible
for the odd terrain on the exact opposite side of the planet (left).
In addition to the heavily cratered terrain, Mercury also has regions of
relatively smooth plains.
Some may be the result of ancient volcanic activity
but some may be the result of the deposition of ejecta from cratering impacts.
of the Mariner data provides some preliminary evidence
of recent volcanism on Mercury.
But more data will be needed for confirmation.
Amazingly, radar observations of Mercury's north pole (a region
not mapped by Mariner 10) show evidence of water ice in the protected
shadows of some craters.
Mercury has a small magnetic field whose strength is about 1% of Earth's.
Mercury has no known satellites.
Mercury is often
with binoculars or even the unaided eye,
but it is always very near the Sun and difficult to see in the twilight sky.
There are several
show the current position of Mercury (and the other planets) in the sky.
More detailed and customized charts can be created with a
More about Mercury
, a new look at the Mariner 10 data
from the 0.5 m Swedish Vacuum Solar Telescope
from Boston University
, ongoing research
and some links
Open Issues
Mercury's density (5.43 gm/cm3) is nearly as high as Earth's.
Yet in most
other respects it more closely resembles the Moon.
Did it lose its light rocks
in some early catastrophic impact?
No trace of iron has been seen in spectroscopic studies of Mercury's surface.
Given its presumably large iron core this is very odd.
Is Mercury much more
completely differentiated than the other terrestrial planets?
What processes produced Mercury's smooth plains?
Are there any surprises on the other half of the surface we've not seen?
Low resolution radar images obtained from Earth show no surprises, but you
never know.
ESA may also build a Mercury orbiter called
but it will launch no sooner than 2012.
Nine Planets - Mercury
1994 - 2015 (C)
A guide to our solar system and beyond.