Relative age and relative dating

For example, the principle of superposition states that sedimentary layers are deposited in sequence, and, unless the entire sequence has been turned over by tectonic processes or disrupted by faulting, the layers at the bottom are older than those at the top.

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So we can infer that coal seam is younger than the faults (because it disrupts them), and of course the upper sandstone is youngest of all, because it lies on top of the coal seam.

Exercise 8.1 Cross-Cutting Relationships The outcrop shown here (at Horseshoe Bay, B. Buff/pink felsic intrusive igneous rock present as somewhat irregular masses trending from lower right to upper left 2. A 50 cm wide light-grey felsic intrusive igneous dyke extending from the lower left to the middle right – offset in several places Using the principle of cross-cutting relationships outlined above, determine the relative ages of these three rock types.

Current scientific evidence shows that the Earth is: c) more than 4 billion years old 2.

Look at the diagram below representing layers of rocks and the fossils buried in them. (The bottom layer is circled)b) Explain how you know which layer is the oldest.

With this in mind geologist have long known that the deeper a sedimentary rock layer is the older it is, but how old?

Although there might be some mineral differences due to the difference in source rock, most sedimentary rock deposited year after year look very similar to one another.

The lava flow took place some time after the diorite cooled, was uplifted, and then eroded.

(Hammerhead for scale) [SE] Figure 8.6b Rip-up clasts of shale embedded in Gabriola Formation sandstone, Gabriola Island, B. The pieces of shale were eroded as the sandstone was deposited, so the shale is older than the sandstone.

Absolute age is the numeric age of a layer of rocks or fossils.

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