ericmurphy
Posts: 2460
Joined: Oct. 2005
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Quote (BWE @ May 12 2006,16<!--emo& ) | AFDave,
Now that I go back and read the list I wrote, I am more curious than when I wrote it. Can you answer these questions?
Others here: Can you answer those questions?
(Without a reference) |
Okay, I'll give your questions a try (without any research or reference to anything other than the questions themselves). And, before you laugh, keep in mind that I don't have an undergraduate degree in anything:
1) I live in the San Francisco Bay Area. The geology of the area is largely the result of the Pacific plate grinding up against the North American plate along the San Andreas fault. The terrane I live on is largely comprised of the Franciscan melange, mixed in with what appear to be large bits and pieces broken off of the Smartville Block which underlies most of the Central Valley in California. The geology of the San Francisco Bay Area is on the order of five million years old, and is comprised of sediments and metamorphic rocks of widespread provenance spread over much of the pacific rim.
2) Most of the fossils in the immediate area of marine origin, mostly dating from the late cretaceous/early Cenozoic.
3) This question is a bit vague, but often various speciation events are the result of geographical/climatological isolation events. Obviously climatological changes will result in differing habitat ranges. An example would be the northerly drift of many commercially-important fish like cod and salmon, which have drifted north as the climate has warmed up. Also, organisms can become reproductively isolated over longer timespans due to tectonic forces operating on continental landmasses.
4) Again, the question is somewhat vague and has more than one potential answer, but one thing a top-level predator in an ecosystem provides is selection pressure on its prey. Of course, it also provides population control.
5) Ridges and trenches are the result of tectonic activity involving the earth's crust and convection cells in the mantle. Trenches result when one oceanic plate subducts under another, as in the Cayman Trench and the Marianas Trench. The most famous spreading center is undoubtedly the Mid-Atlantic Ridge, where upwelling magma creates a spreading center that runs the entire length of the Atlantic. As one moves away from the ridge, one encounters progressively older crustal material. A further observation would be that as the Mid-Antlantic Ridge creates new oceanic crust, the Atlantic Ocean gets larger, while subduction trenches in the Pacific make that ocean smaller.
6) Scientists believe that dinosaurs existed because they see abundant evidence for their existence in the numerous fossils they have discovered, deposited during the ~180 million years that dinosaurs existed (from ~220 mya until ~65 mya).
Estimates for the age of dinosaur fossils result from several converging lines of evidence, principally stratological estimates derived from estimates of sedimentation rates, along with radiological data. Also, estimates of mutation rates along with investigations into primitive and derived characteristics provide additional calibration for the dates of various fossils.
7) In general, the answer to this question probably involves the concept of nested hierarchies. To use an example AFDave should be able to understand: bats and birds seem superficially more similar than bats and chimps. However, cladistically bats nest more readily with chimps than with birds, because bats and chimps diverged more recently than bats and birds. While there are no mammals with feathers (a primitive characteristic), there are indeed mammals with wings (a derived characteristic).
8) The magnetic orientation of the seabed gives us evidence that the polarity of the earth's magnetic field has reversed numerous times over the earth's lifetime, with an irregular period of hundreds of thousands to millions of years. As seabed formed from oceanic spreading centers, the intrinsic magnetism of the rock "froze" in a particular orientation as the magma cooled. The stripes of opposing magnetic orientation in the seafloor moving outwards from spreading centers provides evidence for the creation of new seafloor at spreading centers and for reverses in the earth's magnetic field.
I'm sure there are more than a few errors here, but again, I did no research whatsoever to answer these questions; my answers are literally off the top of my head. So I won't take corrections to this post badly. And any corrections won't present a huge challenge to my world-view, either. After all, if I doubt your criticisms, I can always find out what the scientific consensus is.
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2006 MVD award for most dogged defense of scientific sanity
"Atheism is a religion the same way NOT collecting stamps is a hobby." —Scott Adams
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