"Credit must be given to observation rather than theories, and to theories only insofar as they are confirmed by the observed facts."
Aristotle
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"Credit must be given to observation rather than theories, and to theories only insofar as they are confirmed by the observed facts." Aristotle |
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| About • Correspondence • The Solar System • Biology • General • Philosophy • Geology • Earth Science | ||
Answers to Geology Questions
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Why aren't the continents eroded?
At the current rate, the continents should have eroded much more than they have.
John Harshman:
This is a quantitative claim, and you should back this up with something. Anything. There are all sorts of different rates of erosion happening all over the world. The fastest rates are generally where slopes are steepest, and these slopes are steep because the ground is being uplifted. Every mountain is a race between erosion and uplift. Most mountains today are being eroded at a high rate, but are being uplifted at a slightly higher one.
The answer to your question is that there is a tectonic cycle. Erosion moves material from high areas to low areas, but plate tectonics, causing uplift and subsidence, changes the locations of high and low areas over time. Which is why there are marine fossils on top of many mountains.
Sverker Johansson:
There is even strong negative feedback in the process, that helps to keep it in rough equilibrium. If the continents get pushed up too high, then erosion increases and grinds them down -- but if there is too much erosion and too little uplift, then the continents get flat and erosion effectively stops, until uplift gets going again.
Thomas H. Faller:
The questions as a whole show a remarkable lack of real-world observation and knowledge of any scientific facts. Most questions appear to be based on data that are over-generalized, out-of-date, or just wrong, and a better selection of facts would answer most questions.
This question is [a good example]. There is no indication that the author is aware of any facts of modern geology.
The continents are periodically eroded and then are periodically innundated by the sea and are covered with fresh sedimentary deposits. What he think is being eroded now? Citing "the current rate" shows he is ignorant of the cyclical nature of sedimentation, tectonics, or the changing profile of the continents.
A question for the creationist is why there are rock strata nearly everywhere, in settings that can not be explained by floods (such as lithified desert dune sands or extensive silts or evaporites) if Creation happened?
How did fossils form?
Any sea creature dying and falling to the bottom of a body of water would either decay or be eaten before being slowly covered with silt. Many land animals have been found fossilized. They could not have all been buried under water.
Mark Isaak:
Creationist Claim CC363
John Harshman:
The study of fossilization is called taphonomy, and there's a huge literature on it. Your assertions are just plain wrong. First, there's a great variation in how susceptible different parts of different organisms are to decay. Hard shells are more resistant than soft organs, which is why most of the fossil record consists of snails, claims, and echinoderm skeletons. Predation and decay are reduced in cold, anoxic water. And many burials are not slow but quick, occasioned by such things as slumps, turbidity flows, and floods (don't get too excited; not global floods). Terrestrial fossils are formed in a variety of environments. Water (like rivers) is involved in many but not all cases.
You realize that none of this fits a global flood scenario, don't you?
Thomas H. Faller:
Another question showing basic ignorance of paleontology. Most creatures are destroyed by predation, by decay, by erosion (visit any beach) or by later destruction after becoming part of the strata, due to erosion or subduction into the crust. Only a tiny fraction of the creatures which have lived are preserved today, which accounts for the gaps in the fossil record.
Nevertheless, there are always environments where rapid burial or lack of decay or predation make preservation of body parts likely, and then mineral replacement completes the fossiization process later. All that remains is for erosion or digging to enable us to find the fossils.
Land animals can be buried in sediments in streams, in floods, in lakes, in tar pits, in sand dunes, in bogs and in other land-based traps. Their method of burial is reflected in the sediments they are found in. Not knowing this points to an almost complete lack of knowledge about geology, rather than it being a stumbling block for evolution.
A question for the creationist is why sedimentary rocks world wide show similar progressions of trends in fossils, impossible to explain by hydrological sorting, and illustrating huge quantities of extinct organisms? One formation in North America has enough crinoids pieces to cover the earth.
Where did so much sedimentary rock come from?
A vast majority of the rock that we find was laid down by water.
John Harshman:
Or in water, yes. Especially in epicontinental seas, which during most of earth's history have been much more extensive than they are now. Sedimentary rock comes mostly from erosion of other rocks, mostly from regions of uplift, and from the skeletons of shelled marine animals. If you're saying there's more than there ought to be, you should present some numbers to show this. But how we would expect more sedimentary rock from a single year-long flood than from billions of years of erosion and deposition is quite beyond me.
Sverker Johansson:
A tiny fraction of a millimeter per year, over billions of years, adds up to miles and miles of rocks. Do the arithmetic.
Thomas H. Faller:
This question, of all so far, deserves a "duh". Sedimentary rock is ultimately derived from the weathering of igneous rock or from biological material like shells or silicate organisms. When igneous rock weathers, it forms minerals, clays and the longest lasting product, quartz, or sand. These products are deposited, weathered, re-deposited, re-eroded, and even re-assembled into living things. Limestones and silicious shales are formed from biological material that has been weathered, but it too can be re-deposited and reworked. All rock can be metamorphosed under the right settings, and then weathered again.
The vast majority of the sedimentary rock we find was laid down by water because water is able to supply more energy for transport than wind and gravity is uni-directional. On an airless world like the moon, we should expect meteor impact to be the dominant form of erosion, and ballistic transport or tectonics the main form of transportation.
A question for the creationist is why sedimentary rocks can show evidence of re-working, transport and redeposition that mix rocks of widely varying origin, indicating different processes and different timescales impossible to explain by short-period processes. An example would be a conglomerate made of reworked quartz pebbles, limestone pebbles, metamorphic rocks, alluvial sands and cherts, found in Utah.
Why are stalactites used to prove old age in caves when they have already formed under the Lincoln Memorial?
In just 45 years, these stalactites were almost 5 feet in length. The rate of stalactite formation therefore depends on more than time.
Mark Isaak:
Creationist Claim CD250
John Harshman:
True. It depends also on conditions in the cave, on the amount of dissolved minerals in the water, and on the rate of flow of water.
Thomas H. Faller:
Yes. It does. Cave stalactites are formed as dilute acid, carbonic acid, dissolves the limestone strata in a cave and re-deposit it as the water/acid evaporate along the stalactite column. Where the mix drips frrom the column, stalagmites form on the floor. The Lincoln Monument is composed of calcite-containing rock which is exposed to the acid-containing humidity and rain of the Washington, D.C. area. The term "acid rain" is used to indicate the dissolving power of the precipitation commonly found there. "Acid rain" is what is dissolving the structure of the Lincoln Memorial, at a rate much faster than usually seen in nature or in caves, and transporting it to stalactites.
When caves are opened to outside weather, or are flooded by a change in water level, stalactite production is affected, and cave formations can be dissolved away. Stalactite formation is a balance of supply material, evaporation, and the chemical strength of the transport medium. They aren't constants, even within a cave.
A question for the creationist is why caves are found at elevations of over 10,000 ft, with old-growth stalactites (as indicated by rings), from seafloor-derived limestones (from fossil evidence)? The cave formation and stalactite growth indicate the limestone has been in place for longer than hundreds of thousands of years.
How was coal formed?
There is nowhere in the world that coal (or oil) is being formed today.
John Harshman:
And you know this how? If it's happening, it would be happening far under ground, in strata buried far under other strata.
Thomas H. Faller:
Burial and compression of carbon-rich sediments. Coal is forming in many places today. Besides peat bogs, it is likely forming beneath tundras and coastal swamps. We see coal-production underground where near-surface natural gas is high, like in the Arctic.
The question for the creationist is why coal exists at all, contains fossils, and exists in some locations, such as the Midwest, in regular layers with sandstones, limestones and shales all less than an inch thick, indicating long term periodic rise and fall of sea level complete with changes in fossil fauna over time?
How does one explain bent strata?
The strata had to be bent while it was soft.
John Harshman:
Plastic deformation under high heat and pressure, resulting from being buried under sever miles of sediments.
Sverker Johansson:
And sufficiently hot rock is soft enough. (implicit in your answer -- but given the intellectual level we're talking to, I thought I'd make it explicit)
Thomas H. Faller:
Rocks are plastic over time. Rocks can be bent with sufficient pressure in laboratories, and show features of strain, grain deformation and stress fracturing similar to rocks in situ. Forces sufficient to shear and fracture rocks, as around faults, will deform those rocks near the fault break. Forces act on rocks after they harden, as evidenced by the deformation of fossils within bent rock. Force applied over differing lengths of time will show up as differing patterns of deformation, as the rock is allowed to adjust to stress.
The question for the creationist is why oceanic crust bends and subducts at plate margins, remaining intact to depths of dozens of kilometers? Why should there be any difference between the oceanic crust and continental crust? The MidWest demonstrates that continental crust can serve as sea floor.
Why does one commonly find ancient rocks on top of new rocks?
Mark Isaak:
Creationist Claim CD102
John Harshman:
One doesn't, commonly. Except in regions with lots of thrust faults.
Thomas H. Faller:
This is not common. If it were, the principle of superposition would not account for most strata. The question also pre-supposes there is a means to determine which rock strata is "ancient" or "new", which begs the question creationists are trying to ask. Any faulting which raises older rock can place it over younger rock. Very low angle faults (thrust faulting) can place large areas of older rock over younger rock, but thrust faulting can be detected in place by examination of the contact plane. Faulting and folding, followed by erosion, can place "overturned beds", which are explained by examining the regional stratigraphy and tectonics. They do not occur in isolation.
A question for the creationist is to explain the rule, not the exception. Why is stratigraphy dominated by persistance of rock types, index fossils, aereal erosional surfaces, evidence of concordant depositional environments, evidence of regular and slow sea level change and tectonics?
How do you explain canyons?
It seems natural that the canyon should run the entire length of the river, but there are many places where a river, flowing downhill the entire way, has cut a canyon thousands of feet thick in some places but left some portions of the riverbed level with surrounding land.
John Harshman:
There are all sorts of reasons why canyons of different sorts are cut. The Colorado River in the Grand Canyon area happens to be flowing through an area in which the rocks are being uplifted. It cuts down in the area of uplift to maintain its gradient. Outside the area of uplift, it's in equilibrium.
Thomas H. Faller:
Why should it be natural that canyons run the entire length of a river? Can anyone envision the Mississippi Canyon or the Ohio Canyon? Canyons exist where the steepness of the gradient give flowing water the power to carve into existing rock. Where the gradient is shallow, rivers lose that power. The Grand Canyon, Hell's Canyon and other examples have steeply flowing rivers - both are prime spots for sportsmen seeking rapids to run. When the Colorado river reaches less steep terrain, it slows down and drops its sediment load at its banks, becoming level with the surroundings.
Because topography doesn't usually change back and forth between steep and flat, there aren't many rivers with canyons at more than one spot along their length, but I would guess that there are rivers along the eastern US seaboard that leave the mountains, flatten out, and then hit the Fall Line, which is the remanent of an ancient coastal plain, and spawn waterfalls, and in some cases, canyons again. The Niagara Falls and its gorge is an example of a canyon produced by an abrupt change in topography.
River energy and its cutting power are controlled by slope, and the failure to observe this, and instead to relay on some "natural idea" of how canyons should form demonstrates the basic failure of creationists to deal with the real world.
A question for creationists is to explain the physics of sedimentation. Erosion is subject to the laws of physics. Rocks are eroded more quickly and more deeply by greater force. The size of the particles eroded vary with the energy of the eroding medium. Particles settle through their medium at rates which depend on physical properties. The laws of physics can be applied to sediment grain size, weight and pattern of deposition. So how can the record of stratigraphy be explained in a manner consistant with physics in a way that does not require billions of years to produce the depositional sequences we see?