Science-Technology
See other Science-Technology Articles
Title: At last, a theory about why Denver is a mile above sea level
Source:
TBO online
URL Source: http://tbo.com/ap/national/at-last- ... 0d237e51cc438687b6aec7cbd5f0f5
Published: Mar 13, 2015
Author: Dan Elliott
Post Date: 2015-03-13 19:56:43 by cranky
Keywords: None
Views: 1681
Comments: 7
In this April 14, 2003 file photo, the downtown Denver skyline is pictured, with the foothills, and the Rocky Mountains in the background. Geologists say they might finally know why the Mile High City is a mile high: water. A new theory from the University of Colorado suggests that chemical reactions triggered by water far below the Earth’s surface made this part of the continental plate lighter than surrounding areas, causing it to rise, lifting Denver’s location 5,280 feet above sea level. Geologists may finally be able to explain why Denver, the Mile High City, is a mile high: water. A new theory suggests that chemical reactions, triggered by water far below the Earth's surface, could have made part of the North American plate less dense many millions of years ago, when the continents we know today were still forming. Because plates float on the Earth's mantle, parts of the Western United States might have risen, like an empty boat next to one with a heavy cargo, pushing the vast High Plains far above sea level, according to the theory formulated by geologists Craig Jones and Kevin Mahan at the University of Colorado-Boulder. Their work appeared last week on the website of the journal Geology, and is a big deal for Denver, where the 5,280-foot elevation is a point of pride and a big part of the city's identity. At Coors Field, where the Colorado Rockies play baseball, a single row of purple seats interrupts about 50,000 green ones, marking the mile-high line in the grandstand. Geologists have long been puzzled by how the High Plains could be so big, so high and so smooth. The plains descend gently from roughly 6,000 feet to 2,000 feet above sea level as they stretch for thousands of square miles, from the Texas Panhandle to southern Montana, and from western Kansas to the foothills of the Rocky Mountains in Colorado. It's well established that much of the West was still at sea level 70 million years ago, and that tectonic shifts don't fully explain the High Plains' altitude. The lifting began long after the ancient Farallon oceanic plate was shoved deep under a vast part of western North America and then settled deep into the planet's mantle over millions of years. Why? "Crustal hydration," Jones and Mahan theorize. They suggest that water that had been locked in minerals in the Farallon plate was released because of pressure from the overlying rock and heat emanating from the Earth's core. The water then rose into the continental plate, setting off chemical reactions that turned garnet and other dense minerals into mica and other less heavy minerals, making vast areas of the crust lighter. Jones said the Earth's crust under the High Plains "floats higher" over the mantle, much like a plank of buoyant balsa wood rises higher in the water than a plank of dense pine. The reason crustal hydration happened where and when it did has to do with how steeply the oceanic plate descended, Jones said. At some point, the angle at which the plate was descending became shallower, enabling the released water to rise for reasons that remain unclear, he said. Few geological formations appear so uniform on such a vast scale as the High Plains — the only other known location in the world that's similar is in southern Africa, Jones said. The prevailing theory there is different, involving some other source of buoyance, Mahan said. The composition of rocks found in the High Plains is strong evidence in favor of the hypothesis, Jones said, but it needs more testing, and that was one reason for publishing it. "Do we think this is 'the' answer? No. Could it be 'an' answer? I suppose it's possible," said Jones, who is also a fellow at the Cooperative Institute for Research in Environmental Sciences, a partnership of CU and the National Oceanic and Atmospheric Administration. The theory has merit, according to Ken Dueker, a professor of geology and geophysics at the University of Wyoming. "It's a plausible hypothesis that has some data to support it," said Dueker, who was not part of the team that devised it. One unanswered question, which Jones and Mahan raised in the journal Geology, is what channeled the water up into the North American plate, Dueker said. The Farallon plate also helped form the Rocky Mountains just west of Denver, which soar as high as 14,433 feet. As it moved under the continent, friction caused the North American plate above to compress horizontally, like a rug that bunches up if a foot is dragged across it, geologists say. Cracks opened from that horizontal pressure, and one side was shoved higher than the other, creating the Rockies. Not knowing why Denver is a mile high is a little awkward for Colorado geologists. Jones recalls having to tell a British TV producer a few years ago that he couldn't explain it. "We probably need to figure this one out, guys, because it's kind of embarrassing," Jones said.
Post Comment Private Reply Ignore Thread
Top • Page Up • Full Thread • Page Down • Bottom/Latest
#1. To: cranky (#0)
It always seemed dumb to make a big deal about it. Okay, it's a mile above sea level. So what?
Here's my theory: Mile High City is a mile high because that's where they built it.
If the theroy hasn't been enacted by Congressional vote or later annointment or sanctioning of the majaekal POTUS whiz wand, "what does it matter?"
Bingo! I'm looking forward to their next article discussing their theory on why Chicago just so happens to be located on Lake Michigan.
Want to know what really happened? Ok, start by looking up Neil Adam's "Expanding Earth" video. What he shows is essentially true: the continental plates DO close in the Pacific as well as the Atlantic. He shows WHAT happened: the Earth was once much smaller without the huge ocean gaps. Then it expanded. But he doesn't explain how, or why. So let's look at why made it expand. The continental drift and ocean bottoms are evidence OF the expansion, but don't explain how. Google the National Geographic map of the bottom of the ocean. There's a good one that shows the oceanic ridges. Take a look online at what the mid- oceanic ridges look like. They don't look like mountains on the surface. They look like parallel ridges, separated by a deep black crack, a chasm that goes down into darkness in the depths of of the earth. Now look at that National Geographic Map and realize that the "crack" that is the center of the mid-oceanic ridges girdles the whole globe, those ridges are all linked together in one long earth-girdling crack. Now Google water compression. We all learned the three states of water: gas, liquid and solid, and water's melting, freezing and boiling point. Of course those state-change points are at standard temperature and pressure. Under normal conditions at the earth's surface water barely compresses. But under great pressures, it does compress. The water at the bottom of the Marianas Trench, for example, is compressed by the weight of the water column above it. The compression is a few percentage, a measurable amount. Under great pressure, water compresses. Recent studies of compressed water - the things you googled when I asked you do - reveal that at great pressures, water compresses down to 40% of its normal size, and becomes a non-crystalline sold. The weight of the earth's crust down 80 miles or so is sufficient. So, here is what happened. When the earth formed, the crust of the earth cooled upon and compressed, by its weight, a huge volume of water. That compressed water remained there for a time. At a certain point, however, the water burst through the crust at a point. This, then resulted in a rapidly expanding crack that girdled the world, with water under tremendous pressure bursting forth all along the cracks in vast geyser-like fountains. The small earth was covered with water, as the water rushed out. But that was not the only way that the pressure was released. A vast amount of water under vast pressure was being released, but the closed "eggshell" of the earth no longer restrained the water, so the compressed water also released its pressure by expanding. Now that the structural integrity of the earth's crust was not longer held together as a solid shell, the whole shell itself, the pieces, expanded outwards as the earth rose like a souffle. This caused exposure of the underlying mantle, which rapidly expanded as new sea bed (the sea bed is not very old). The earth rose like a souffle, until the pressure of the compressed water was released both by expansion (the Neil Adams movie) AND the venting of the water through the "fountains of the great deep". The land, now as continents, re-emerged from the flooded globe because the world literally got bigger, due to hydraulic expansion. You can see the evidence of it both in the continental plates - and the fact they close in the Pacific, in the youth of the ocean bottoms, and in the mid-oceanic ridges, that all link together in that world-girdling crack. That's why Denver's a mile high: that's where that flat surface plate expanded too before it reached equilibrium. That's why there are non- volcanic, non-mountainous high plains all over the earth. That's why, that's how, and that's when.
I doubt that very much. To compress any liquid requires an extremely watertight container of prodigious strength. The earth's crust is pretty porous.
There are three kinds of people in the world: those that can add and those that can't
Actually, the water at the bottom of the Marianas Trench, an open "container" is compressed about 7% by the weight of the water column above.
...a big deal for Denver, where the 5,280-foot elevation is a point of pride and a big part of the city's identity.
#2. To: cranky (#0)
#3. To: cranky (#0)
#4. To: Logsplitter (#2)
"Here's my theory: Mile High City is a mile high because that's where they built it."
#5. To: cranky, Too Conservative, redleghunter (#0)
#6. To: Vicomte13 (#5)
When the earth formed, the crust of the earth cooled upon and compressed, by its weight, a huge volume of water.
#7. To: cranky (#6)
Top • Page Up • Full Thread • Page Down • Bottom/Latest
[Home] [Headlines] [Latest Articles] [Latest Comments] [Post] [Mail] [Sign-in] [Setup] [Help] [Register]