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One of the very foundations of evolution and popular science today is the "geologic column. Although not found in all locations and although it varies in thickness as well as the numbers of layers present, this column can be found generally over the entire globe.
Many of its layers can even be found on top of great mountains - such as Mt. Everest and the American Rockies. In some places, such as the mile deep Grand Canyon, the layers of the column have been revealed in dramatic display.
Certainly the existence of the column and its layered nature is quite clear, but what does it mean? Is it really a record of millions and even billions of years of Earth's history?
Or, viewed from a different perspective perhaps, does it say something else entirely? As one looks at the geologic column, it is obvious that the contact zones, between the various layers, are generally very flat and smooth relative to each other though the layers may be tilted relative to what is currently horizontal or even warped since their original "flat" formation.
Many of the layers extend over hundreds of thousands of square miles and yet their contact zones remain as smooth and parallel with each other as if sheets of glass were laid on top of one another before they were warped. And yet, each layer is supposed to have formed over thousands if not millions of years?
Wouldn't it be logical to assume that there should be a fair amount of weathering of each of these layers over that amount of time? But this expected uneven weathering is generally lacking see illustration. Long term erosion always results in uneven surfaces and this unevenness is only accentuated over time.
How then are the layers found throughout the geologic column so generally even and smooth relative to each other? This presents a problem since very old sediments, dating in the hundreds of millions of years, remain atop all the continental shelves - wonderfully preserved despite many tens of and sometimes hundreds of millions of years of erosive pressure?
This problem has been well recognized for some time now. Back in Dott and Batten noted: The student has two courses open to him: It is just that the layers above have been eroded away. In this line of reasoning, consider that the current layer toping the region around the Grand Canyon, the Kaibab, was once buried under sediment no thicker than 2, meters for a total thickness of around 3, vertical meters of sediment measuring from the bottom Tapeats Sandstone to the topmost Brian Head Formation Tertiary sediments.
In this light, consider the popular belief that the nearby Rocky Mountain region began its most recent uplift, via tectonic forces, some 70 million years ago, with an additional uplift some 25 million years ago that raised the Rockies up an another 1, to 2, meters.
One might very reasonably wonder how much vertical erosion should be expected in such an uplifted region over the course of 70 million years? Well, before the Glen Canyon Dam was built, the average sediment transport rate through the Grand Canyon was measured to be aroundtons per day.
Since the Colorado River is supposed to have carved out the Grand Canyon in around 5. Well, if we multiply the current daily erosion rate by days we get about 2.
Multiplying this number by 5. But, what about the Colorado Plateau itself? Well, there seem to be two different theories. One theory suggests that the most recent uplift of the Kaibab Plateau the region of the Colorado Plateau that is located right around the Grand Canyon region started some 17 million years ago and the other suggests that the this uplift actual started some 35 million years ago.
Either way, the overall uplift of the Colorado Plateau is supposed to have started a bit later at around 15 million years ago. Some suggest that the Colorado Plateau was already uplifted a few thousand feet before it started its most recent uplift, while others believe that it was "near sea level" just before its latest uplift.
This makes me wonder how the relatively young Tertiary sediments survived atop the Grand Staircase over the course of some 15 million years of erosive pressure. Was there really over 2, meters of sediment covering these remaining tertiary sediments?
I mean really, a couple thousand meters of sediment was definitely removed from over the gentle dome-shaped uplift of the Grand Canyon region in a mere 5 or 6 million years while the topmost sediments of the Grand Staircase were hardly touched in 15 million years?
Also, if 2, vertical meters of sediment was removed from the Kaibab Plateau after the local dome shaped uplift, where are the side channels, around the dome, formed by the rivers that took this large amount of sediment away from this region? As far as I can tell, there simply are no such significant pathways of sediment removal around this dome-shaped region.
Yet, wouldn't they have to be there if in fact such a large amount of sediment were in fact removed from atop this dome-shaped region over many millions of years of time?
However, the rate of uplift is being matched by the rate of erosion, with little or no change in elevation. So, how did the sedimentary layers last all that time in the Rockies? What is going to overcome even a bare minimum of 7, meters of vertical erosion?Soil Erosion has been a major issue in the past and will become an even greater issue in the future as population growth continues to expand and land resources are more intensively used, often to a .
The 9th International Conference on Scour and Erosion will take place in Taipei, Taiwan from November The conference provides a platform for scientists and engineers from around the world to exchange ideas and share advances in research and practice on the scientific and engineering challenges related to scour and erosion.
Agriculture. Agriculture is one of the most significant causes of deforestation. The first form of agriculture that will be examined is slash-and-burn agriculture.
Dec 14, · This is a “what if” interview from the World Economic Forum’s Risk Response Network. To view the rest of the series, click here. It’s a strange notion, but some experts fear the world, at its current pace of consumption, is running out of useable topsoil. The Living Soil: Texture and Structure.
Soils are made up of four components: minerals, air, water, and organic alphabetnyc.com most soils minerals represent around 45% of the total volume, water and air about25% each, and organic matter from 2% to 5%. After the Fire: Indirect Effects on the Forest Soil Fire's most significant indirect effects on soil are caused by the alteration of standing vegetation and the consumption of organic matter within and beneath the forest floor (DeBano et al.
, Neary et al. ).