The relative dating principle of

Just as Sherlock Holmes used his power of observation to decipher the clues to a suspect's past actions, we will let the blemishes and behaviors of the rocks tell us their past story. ) Remember that relative dating involves determining "which came first" rather than "exactly when did this happen." The first step to untangling the geologic history of an area is often to figure out what happened first, second and third, etc.

without knowing the absolute ages at which the rocks themselves formed.

Cliffs, road cuts, and non-vegetated landscapes allow us glimpses into geology which is often hidden from view.

Cliffs and road cuts are "side views" or "geologic cross-sections" of the topography which show the relative positions of various rock layers and structures at a given spot.

Complete the sequence correctly and explain the logic and principle behind your choice for each event.

Your explanations are as important as the correct sequence in earning the points for this question.

Question 3 (3 points): Finally, return to the list of hypothetical geologic examples and click on "two intrusions." Again, complete the sequence correctly and explain the logic and principle behind your choice for each event.

This is a much more difficult exercise than the previous two because we will find several possibilities for the sequence of geologic events .

As geologists piece together the information at various outcrops, they can begin to assemble a "geologic map" (like a road map) of an entire region (consisting of many square miles).

This map displays the large-scale (also called "regional") geologic features they have inferred are present beneath the landscape.

Applying the principles of relative dating to these rock exposures (also called "outcrops"), we can reconstruct the sequence of events that created the geologic features which we see.

Events can be the deposition of a sedimentary layer, the eruption of a lava flow, the intrusion of magma to form a batholith, a fault (break) in the rock that shifts one side relative to the other side (and causes an earthquake), a fold that bends and distorts rock layers, or any number of other geologic processes.

Question 7 (8 points): Using the relative dating method you have now practiced, derive the history of the hypothetical landscape on page 173 (also shown below).

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