Watching the river, 3/18/10
in Earth and Space Science, Physical Science, The Water Cycle, Weather and Climate, and Forces of Nature
If you're visiting the Science Museum of Minnesota, look out the windows from the Mississippi River Gallery on level 5. If you're in downtown St. Paul, stop by the museum and look at the river from the overlook on Kellogg Plaza. (City officials are asking folks not to flock to areas where barriers are going up - especially Harriet Island - but the view from in or around the museum is spectacular and safe.)
Kate's photos, 3/18 (3): Looks peaceful, doesn't it? Still, the city is warning people to stay off of the river, out of the low-lying parks, and away from Harriet Island and Water Street.
Courtesy Kate Hintz
The Mississippi is going up FAST today, and forecasters expect that the river will officially reach "flood stage" by early this afternoon. (It's 10:45am, and the river's at 11.67'. It's risen a foot and a half in the last 24 hours, should reach 12' ("action stage") pretty soon, and 14' ("flood stage") by late today.
Kate's photos, 3/18 (2): Look across the river to the floodwall: that's the high-water mark for the 1965 flood, the highest in recorded history. That year, the river crested here in downtown St. Paul at 26.01' and marked the end for the communities then down on the river flats.
Courtesy Kate Hintz
Kate's photos, 3/18 (1): Shepard/Warner roads will close from Chestnut Street to US 61 starting Saturday morning, and could remain closed for weeks. Take your river sightseeing drive/bike ride/walk before then!
Courtesy Kate Hintz
So what's going on around the river?
- The city has closed all city boat launches and temporarily banned all recreational boating within the city limits.
- Water Street will be entirely closed, starting this afternoon.
- Hidden Falls and Lilydale regional parks are closed.
- Flood barriers are going up at the St. Paul downtown airport and at Harriet Island.
- Harriet Island will close once the river reaches 17'.
- Warner/Shepard Roads will be closed from Chestnut Street to US 61 starting Saturday morning in preparation for the construction of a temporary levee that could withstand river levels to 26'. These roads could be closed for weeks, depending on the extent of the flooding.
Here's the latest hydrology graph:
3/18 hydrology graph, 10:15am
Courtesy USGS
Tags : High and fast
in Earth and Space Science, Math, The Water Cycle, Weather and Climate, and Forces of Nature
Look out the window or walk down the street to nearly any river or stream in Minnesota right now and you are likely to observe two things about the river:
- it is getting deeper (or “rising” in relation to the banks); and
- it appears to be moving faster.
You can, of course, confirm these observations by investigating reports from gauging stations along these rivers, maintained by the U.S. Geological Survey. (See data for the gauging station serving downtown St. Paul.) But what is really happening?
It may be high and fast...: ...but (as of today) the Mississippi at St. Paul is still in a bankfull state.
Courtesy Liza Pryor
Until a river flows over its banks, it is considered to be in a “bankfull” state. In this state, the water flowing through the river is confined to a relatively fixed channel area. Simply put, floods occur because more water is being introduced into this channel from upstream, due to snowmelt, heavy rains, or a dam breach. As this added volume of water moves through a fixed area, it both increases in velocity and in depth until it overflows the banks, at which point some, but not necessarily a lot, of the volume and velocity moving through the channel are reduced.
Scientists call the rate of flow through a channel “discharge." Discharge is defined as the volume of water passing through a given cross-section of the river channel within a specified period of time.A simple equation for determining discharge is
Q = D x W x V
where Q = discharge, D = channel depth, W = channel width and V = velocity.
Looking at this equation, it is easy to see that if discharge becomes greater and channel width is fixed, then an increase in both volume and depth (or height relative to the banks) is likely to be the cause. Discharge can be measured in cubic feet per second or cubic meters per second, for example.
But is the river flowing at the same rate at the surface as it does along its banks and beds? Understanding this requires investigating some more detailed equations, as the banks and bed introduce friction, which affects the rate of flow.
To learn more about rivers and how they flow, you may want to check out the works of Luna Leopold, and M. Gordon Wolman. In particular:
- Leopold, Luna B. (2006, reprint). A View of the River. Harvard University Press; and
- Leopold, Luna B.; Wolman, M. Gordon; and Miller, John P. (1995). Fluvial Processes in Geomorphology. Dover Publications, both classics for understanding how rivers work.
Also, check out our full feature on the 2010 Mississippi River flooding.
Watching the river, 3/16/10
in Earth and Space Science, Physical Science, The Water Cycle, Weather and Climate, and Forces of Nature
All day, up in the Mississippi River Gallery, people have been stopping to look out the window and watch the river.
Here's how the US Geological Survey sees it:
Mississippi River, actual vs. forecast, 3/16/10, 1pm
Courtesy USGS
The river's rising, but not as fast as yesterday. And yesterday's rise outpaced predictions by almost a foot, but today the rise matches the predicted curve almost exactly.
So what are folks seeing out the window? Take a look.
Also check out our full feature on the 2010 Mississippi River flooding.
Watch the steps: They're a good benchmark.
Courtesy Liza Pryor
Raspberry Island: Still high and dry
Courtesy Liza Pryor
Looking upstream: You're still looking at Harriet Island. But low-lying areas of Lilydale (upstream, south side of the river) get inundated when the river reaches 14 feet or so. Right now, that's predicted to happen sometime after 7pm on Sunday, 3/21.
Courtesy Liza Pryor
Science Friday logo
Courtesy Science FridayIt's Friday, so it's time for a new Science Friday video. This week,
"What is the future of sustainable architecture? Washington University's Tyson Living Learning Center in Eureka, MO, achieves the Living Building Challenge--a set of green guidelines that measure a building based on its performance. The building's architect Dan Hellmuth, of Hellmuth & Bicknese Architects in St. Louis, and Kevin Smith, associate director of Tyson Research Center, point out some of the Center's greenest features."
Chilean quake sped up Earth's rotation, tipped planet's axis
Earth spins faster
Courtesy NASA If you read the post about how earthquakes differ, you would know that in the Chile earthquake, a large amount of the Earth's crust plunged under its neighboring crust, bringing it closer to the center of the earth.
Just as Olympic figure skaters spin faster when their arms move closer to their body, the Earth is now spinning faster making our day about 1.26 microseconds shorter than it was before the quake.
Earth was also slightly tipped off balance, like when a spinning skater brings in one arm but not the other. The planet's axis tilted about 8 centimeters. This is insignificant compared to other wobbles measuring several meters resulting from winds and ocean currents.
Asteroid found guilty of killing dinosaurs!!
in Earth and Space Science, Life Science, and Biological Populations Change Over Time
What sent the dinosaurs packing?: The number one suspect, a gigantic asteroid, has finally been convicted of the crime.
Courtesy Mark RyanAfter studying all available evidence and listening to alternative theories (and despite no eyewitnesses), a panel of 45 international scientists has decided it was a huge asteroid that killed all the non-avian dinosaurs some 65 million years ago.
The asteroid, described as a 7 mile-in-diameter chunk of space rock, has been the prime suspect in the ruling reptile’s demise ever since scientists Luis Alvarez and his son Walter first identified a one-inch layer of iridium in Late Cretaceous-age rock exposures throughout the world. The layer was located exactly at the point in the rock record where the Cretaceous period ended, and the Tertiary period began (K-T boundary). 
Smoking gun for dinosaurs' demise: K-T Boundary with 1-inch iridium layer (arrow) exposed 10 miles west of Trinidad, Colorado. The element iridium is very rare on Earth but concentrated in meteors and comets. The same iridium layer is found in several exposures around the world, and corresponds in age with the Chicxulub meteor crater in Mexico's Yucatan Peninsula. The layer marks the end of the Cretaceous era, and no non-avian dinosaur remains have ever been found above the boundary. The coal layers above and below the iridium suggests a swampy environment when the layer was laid down in this area of Colorado.
Courtesy Mark RyanThey predicted a meteor impact crater of the same age would be found as the source of the iridium since the element is rare on Earth but common in outer space. Then in 1990 their predictions were verified when the Chicxulub impact crater was discovered in Mexico.
Although the impact site was mostly submerged off the north coast of the Yucatan Peninsula, samples taken from it dated to the end of the Cretaceous period. This and other corroborating evidence helped bolster the killer asteroid hypothesis as the primary theory for the extinction event that wiped out 70-75 percent of life on Earth including non-avian dinosaurs, and other large reptiles. The asteroid is estimated to have slammed into Earth traveling 10 times faster than a rifle bullet, and released the energy of a billion atomic bombs. The impact instantly vaporized a large area of terrain, and sent an explosion of dust and rocky debris up into space, much of which fell back into the atmosphere in a fiery rain. It left a crater 110 miles across, and a cloud of dust circling the planet for weeks. The diminished sunlight would have disrupted the environment severely, including the food chain. Mammals and other smaller creatures were able to survive across the boundary and flourish in later periods.
But not everyone was convinced by the evidence. Other causes for the mass extinction, such as extreme volcanism in India, falling sea levels, disease epidemics, and even fungal infection were all tossed around as possible culprits.
But in the end it seems the evidence implicating the asteroid in the K-T* extinction event was just too strong, and after much deliberation, the impact has been determined as the official cause of death. The panel published its decision in the latest issue of Science.
*“K-T” stands for Cretaceous-Tertiary, however, use of the term Tertiary is being discouraged now, and the time span it occupied has been replaced with the Paleogene and Neogene periods. So a more proper, up-to-date term would be Cretaceous-Paleogene or K-Pg extinction event.
LINKS AND SOURCES
More about dinosaur extinction
BBC story
Impact theory counterview
Strike-slip fault
Courtesy USGSLast weekend’s massive magnitude 8.8 earthquake off the coast of Chile released 500 times the energy generated by the magnitude 7 earthquake that hit in Haiti the month before. Damage is extensive in both countries but so far Haiti seems to have taken a worse hit than Chile, despite suffering a less-powerful quake. In fact, there's news today that the death toll in Chile has been lowered, which is unusual with earthquake tolls. They're usual revised upward. So why the discrepancy between the two quakes? There are several reasons but a big one is the types of earthquakes involved.
The Haiti tremblor occurred along a strike-slip fault where stress is created as two tectonic plates (in Haiti’s case, the Caribbean plate and North American plate) scrape and grind past each other in opposite directions, like two cars trying to squeeze past each other on a single lane bridge. Tension builds as the plates catch and grind and energy is released in fits and starts in the form of tremors. California’s San Andreas fault is a classic strike-slip boundary. There the Pacific plate is moving in a northwesterly direction beside the North American plate.
Subduction zone: Megathrust earthquakes occur near subductions zones.
Courtesy USGSWith a subduction zone megathrust quake – like that which occurred in Chile - it’s more like a head-on collision, where a lighter oceanic crust slams into a heavier continental crust and pushes (or is pulled) beneath it. This creates tremendous tension which eventually gets released, and when it is does, megathrust earthquakes can sometimes occur. They don’t occur all the time, in fact, megathrust earthquakes are rare – only fourteen have been recorded in history – but they only happen in subduction zones, like the one along the coast of Chile where the oceanic Nazca plate is subducting beneath the continental South American plate. Chile’s Andes mountain range rose up as a result of this subduction.
To give an idea of the incredibly huge amount of energy involved with the Chilean quake, it’s been estimated the jolt shifted Earth’s axis 3 inches, caused the planet’s entire mass to contract, become denser, and it’s rotation to speed up, thereby shortening the length of a day by 1.26 milliseconds! (see story)
The nearness and depth of an earthquake’s epicenter is another factor in the amount of perceived intensity and actual damage (measured using the modified Mercalli Intensity Scale), and this figures in the Haiti-Chile comparison. Haiti’s tremblor occurred six miles below the surface, and within ten miles of the severely over-populated capital of Port-au-Prince. That’s a fairly shallow earthquake, so the intensity level was high. Chile’s earthquake was centered 22 miles underground and five miles offshore, more than 70 miles from the nearest large population center (Concepcion).
Haiti’s capital is also built on loose soil that’s been eroded and carried down from the hillsides, and since earthquakes are rare in the region, the poor island nation is ill-prepared and under-equipped to deal with them. Building construction is flimsy, and collapsed easily when shaken, even by many less intense after-shocks. Chile, however, is on solid bedrock, both geologically and in regards to their central government. The country has a long history of dealing with the many quakes that occur there (the normal-sized ones anyway), and has had building codes in place since the 1920s.
MORE EARTHQUAKE INFO
More earthquake information
USGS earthquake page
Frozen in time: Unique fossil shows snake coiled among nest of dinosaur eggs and titanosaur hatchling.
Courtesy PLoS Biology
Diagram of fossil
Courtesy PLoS BiologyCheck out this amazing fossil showing the remains of a snake coiled around a nest of dinosaur eggs, including a nearby titanosaur hatchling. The fossil was found 26 years ago in northwestern India, and was originally thought to contain remains of eggs and baby dinosaur bones. But recent re-evalutions revealed some of the bones were actually those of a new species of snake named Sanajeh indicus. The incredible 67 million-year-old fossil is the first of its kind, and suggests that snakes preyed on dinosaurs, just as they prey on birds today. A newly hatched titanosaur would have been easy pickings for the 11.5 foot S. indicus, but an adult titanosaur - which grew to more than 100 feet in length - would have been another story. Scientists think the unique Cretaceous fossil resulted from an ancient landslide that buried the snake just when it was about to go after its next meal. Here's a photo of the incredible fossil and along with a diagram of what it contains. You can read the whole story at PLoS Biology where the research has been published.
Rex in the hen house
Courtesy Mark RyanA new study came out last week that appeared destined to shake up the current line of thought that birds descended from dinosaurs. Birds share common traits with some dinosaurs, including furculas (wishbones), hollow bones, and other skeletal features, which scientists have interpreted to mean the former descended from the latter. But now a new study by researchers at Oregon State University, it may have happened just the opposite way.
"We think the evidence is finally showing that these animals which are usually considered dinosaurs were actually descended from birds, not the other way around," said John Ruben, a professor of zoology at OSU, and the study’s lead author.
The study involved the fossil of a Microraptor, a dromaeosaurid dinosaur with evidence of feathers on both its arms and legs. Studying the skeletal remains, Ruben and his colleagues constructed 3-dimensional models that they tested for flight capabilities. Their study showed Microraptor’s structure better suited to be glider rather than a flyer. From this Ruben extrapolated that it made more sense that Microraptor descendents came down from the trees and eventually evolved into flightless birds we call dromaeosaurs or raptors.
"Raptors look quite a bit like dinosaurs but they have much more in common with birds than they do with other theropod dinosaurs such as Tyrannosaurus," he said. The study appears in the journal for the Proceedings of the National Academy of Science (PNAS).
Sounds good at first, and I have to admit I was smitten with the idea. But not everyone feels the same way.
Over at the Smithsonian’s Dinosaur Tracking blog, freelance science writer Brian Switek has pointed out that Ruben’s proclamation is “actually only a commentary, or the equivalent of an opinion piece.”
He then goes on to point out some of the flaws in Ruben’s argument, particularly the uncertainty surrounding Microraptor’s place in the evolution of flight, and the lack of reasonable evidence that Velociraptor wasn’t a dinosaur. Switek doesn’t think Ruben’s claim stands up to scrutiny.
But what annoys Switek most is how the media inundates the various outlets with this kind of science news, giving it wide distribution and often, undeserved credibility.
“In this increasingly fragmented media landscape, knowledgeable science writers who recognize a fishy story when they see one are getting outnumbered. More often, websites and newspapers simply reprint press releases issued by universities and museums (science writers call this “churnalism”), and this policy sometimes lets questionable science slip through the cracks.” – Brian Switek
One of the reasons for this is the internet. There's just a huge amount of time and space that requires constant feedings of content now. It does make things difficult to sort through. There have been times I’ve begun researching some new science story to post on Science Buzz only to become frustrated with details that don’t seem to add up, confusing statements, info that counters other info, and outright misinformation. Some of it may be due to the writer(s) not being able to properly articulate or distill a particular idea or hypothesis for the general reader (I know I suffer from this occasionally). Sometimes it’s due to the fact that many science writers lack access to the papers themselves (most science journals require paid subscriptions to access anything beyond an abstract of the story), so writers are left with relying on press releases and abstracts or another writer’s thoughts on the subject (like I’m doing here). But other times it ends up being that there’s no real story at all, just a rehash of something from months or years ago that somebody figures needed to be in the headlines again.
To this end, paleontologist Dave Hone over at his Archosaur Musings blog recently posted “A guide for journalists reporting on dinosaur stories” that deals with some of issues raised here. It’s worth reading.
Science Buzz has also covered science writing issues in previous posts.
How to read/write science news
Bad Science Journalism
SOURCE and MORE INFO
ScienceDaily.com story
Microraptor gui: Bird or Dinosaur
Origin and Evolution of Birds
Crew of the Starship Enterprise all dead
in Earth and Space Science, Structure of Matter, and Energy Transformations
Space travel kills you: Well, probably not you, but it would kill these two BFFs.
Courtesy JGordonHeyo, Buzzketeers. Any Starketeer Treketeers out there?
Yes? Well check this bit of fun science out: a Professor at Johns Hopkins says that traveling at near-light speeds in a space ship (as folks often do in science fiction) would have the delightful effect of almost instantly killing everyone on board.
Aw, whoops. Did I say "fun"? I meant the opposite of fun.
See, it'd obviously be no good to run into a big chunk of rock while flying around super fast in outer space, but (fortunately) big chunks of rock are really pretty rare way out in space. That's not the problem. The problem is the tiny stuff. The really, really tiny stuff.
Here on Earth, each cubic centimeter of air has about 30 billion billion atoms in it. (That's right—two "billions.") In outer space, however, each cubic centimeter of space might have 2 atoms in it. Two lonely, harmless little hydrogen atoms, drifting around, looking for friends. That low-density of matter is no problem for a low-speed ship—it'd just zoom right through them—but for a ship approaching the speed of light, they could be a huge problem, according to this professor.
Because the ship would be going so fast, the hydrogen atoms would "appear highly compressed, thereby increasing the number of atoms hitting the craft." There's something here about Einstein's special theory of relativity here, but, you know, blah blah blah.That stuff is complicated. I think if it like going running on a buggy night—if you run fast through a cloud of bugs, more of those bugs are going to hit you, and harder. (The moral there being: run with your mouth closed, and run slowly, especially if you're naked.)
So, because so many of the hydrogen atoms are hitting the ship, and because the ship is going so fast, it would be like turning a giant particle accelerator on the ship (except, in this case, the ship is being accelerated into the particles, not the other way around, but the effect is the same). It would be like getting hit with approximately the same amount of energy as if you stepped into the beam of the Large Hadron Collider. Even with a 4-inch-thick aluminum hull, 99% of the hydrogen would blast through the ship as radiation, frying the electronics and killing the crew in seconds. Sad.
You can't wrestle a particle beam, Kirk.
Still, maybe there are some Trekkies and physicists out there who can make us all feel a little better about this? The Johns Hopkins professor clearly knows a ton about radiation, but maybe he's not such an expert on space, or about the physics of Star Trek. I'm certainly not. Don't they warp space on that show? So that they aren't traveling though billions of miles of space (and all that dangerous hydrogen), but are skipping from one spot to another? Something like that? Help me out here. The image of Spock dying of radiation poisoning (again) makes me cry salty tears.
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