It's All Relative EarthCache
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The coordinates listed above are for the locationof the bluff itself. It can't actually be viewed from these coordinates. Additional waypoint coordinates are given where the bluff can be viewed from. Earthcache questions are provided under hints for easier access for those using a gps that has paperless caching capability.
This earthcache will introduce the concept of geological time. The span of time from the moment the Universe was created through today is known as deep time. Scientists have determined that the universe is 13.8 billion years old. So deep time then is 13.8 billion years. The part of deep time that has been captured in rocks and minerals of the Earth and other planets is geological time. The oldest rocks formed on the Earth were found in Canada and have been dated to be 4,030 million years old. There have been zircon minerals found in younger rocks from Australia that are dated to be 4.4 billion years old. The oldest meteorites found on the Earth have been dated at 4.5 billion years old. These meteorites are thought to have been formed at the same time as the Earth so scientists currently date the Earth at 4.5 billion years, just a small part of deep time.
Two methods are used by scientists to record geological time- absolute and relative time. Absolute time assigns an age in years to a rock or mineral while relative time determines a layer of rock to be older or younger than another layer.
Radiometric dating is used to determine the absolute time of a rock or mineral. It uses radioactive decay rates of atoms to determine age. It is most useful in dating igneous rocks because the atoms used to measure decay are trapped in a mineral when it is formed. Since sedimentary rocks are made from the erosion of other rocks, radiometric dating will give you the age of the original rock not that of the sedimentary rock.
Relative time is when geologists determine the sequence of geologic events in an area relative to one another. A good way to think of this is like when you place newspapers in a stack after your done reading them. The papers at the bottom of the stack are older than those at the top. Geologists have developed a set of principles to use as guidelines, in order to help understand the relative ages of rocks.
Principle of “uniformitarianism”- this says that the processes operating in that past did so under the same laws of physics and chemistry as today. For example, in the past water has carried sediment from higher altitudes to lower altitudes just as it does today.
Principle of original horizontality- when originally deposited, sedimentary strata are pretty much horizontal unless deformed by movements of the Earth’s crust.
Principle of superposition- in any section of undisturbed sedimentary rocks, the oldest strata is at the bottom and the youngest is at the top.
Principle of faunal succession-this helps correlate rocks across large distances by comparing fossils. The idea is that rocks of similar ages contain fossils of similar types, some of which do not appear in any other layer. The older fossils appear in the bottom while younger ones appear in the top.
Principle of cross-cutting relationships- a rock body or feature that cuts across another rock body or feature is the younger of the two.
Principle of inclusion- this principle can apply to sedimentary and igneous rock. If a rock body contains inclusions of preexisting rocks, the rock body is younger than the rocks from which the inclusions were derived.
Geological Time Scale- before radiometric dating geologists grouped layers of rock into time groups. The time scale is divided into the following categories from the largest to the smallest time divisions:
Eon- Era- Period- Epoch- Age
Once radiometric dating was developed it confirmed the relative age correlations that geologists had made over the last 150 years.
Chattanooga is located in the Appalachian Basin. The Chattanooga area contains sedimentary rocks from the Paleozoic Era of the Early Cambrian through the Early Permian ages. Chattanooga shale has drawn interest from energy companies for its natural gas deposits. The karst activity in the limestone of Lookout Mountain has drawn visitors to such sites as Ruby Falls, an underground waterfall, located in a cave carved in the limestone. It is also the limestone in this area we are going to focus on in this earthcache. Located at the above coordinates is a limestone bluff overlooking the Tennessee River. If you go to the viewing coordinates you can get a good view of the bluff from the pedestrian bridge. To receive credit for this earthcache message me the answers to the following:
1. The limestone of this bluff is from which geological time era?
2. Are you able to observe the Principle of original horizontality in the bluff?
3. Using the Principle of superposition how does the age of the rock layer at the river surface compare to that at the top of the bluff?
4. Estimate the height of the bluff.
5. Optionally include a picture of your visit to the earthcache.
sources: www.earthcacheacademy.org
https://en.wikipedia.org/w/index.php?title=Geology_of_the_Appalachians&oldid=670731716
http://www.hikelookout.org/history/geology.php
Additional Hints
(Decrypt)
Gb erprvir perqvg sbe guvf rnegupnpur zrffntr zr gur nafjref gb gur sbyybjvat:
1. Gur yvzrfgbar bs guvf oyhss vf sebz juvpu trbybtvpny gvzr ren?
2. Ner lbh noyr gb bofreir gur Cevapvcyr bs bevtvany ubevmbagnyvgl va gur oyhss?
3. Hfvat gur Cevapvcyr bs fhcrecbfvgvba ubj qbrf gur ntr bs gur ebpx ynlre ng gur evire fhesnpr pbzcner gb gung ng gur gbc bs gur oyhss?
4. Rfgvzngr gur urvtug bs gur oyhss.
5. Bcgvbanyyl vapyhqr n cvpgher bs lbhe ivfvg gb gur rnegupnpur.
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