Relative dating exercise 1

26-Sep-2020 11:29

Include all the events which can be inferred from the drawing.

List which relative dating principles apply to the order of each event.

When did all this faulting take place (that is, between the times of which two sedimentary layers did the faulting occur)? Notice the "Great Angular Unconformity" shown on the North Half of the profile.

This is not labeled as such -- but see how the rocks at the bottom of the profile have been tilted while the younger rocks on top are horizontal.

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.

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.

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).Also an igneous intrusion is present (labeled T) and a fault is present (labeled A).