As you pass by an excavation in the street, you see a cross section showing paving at the top, soil below the paving, and bedrock at the base. You also notice that a vertical water pipe extends through a hole in the street into a sewer in the soil. What can you say about the relative ages of the various layers and the water pipe?
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Why did the nineteenth-century geologists constructing the geologic time scale find sedimentary strata deposited in oceans and shallow seas more useful than strata deposited on land?
The theory of evolution suggests a “principle of floral (plant) succession” to complement Smith’s principle of faunal succession. Why do you think Smith relied primarily on faunal fossils rather than floral fossils in his stratigraphic mapping?
In studying an area of tectonic compression, a geologist discovers a sequence of older, more deformed sedimentary rocks on top of a younger, less deformed sequence, separated by an angular unconformity. What plate tectonic processes might have created the angular unconformity?
A geologist documents a distinctive chemical signature caused by organisms of the Proterozoic eon that has been preserved in sedimentary rock. Would you consider this chemical signature to be a fossil?
Is carbon-14 a suitable isotope for dating geologic events in the Pliocene epoch?
How does determining the ages of igneous rocks help to date fossils?