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Relative Time:. Ages of events are placed in order of occurrence. No exact date is identified. Ex. WWI and WWII I am the second child in my family. Absolute Time:. identifies the exact date of an event. Ex. 65 Million Years Ago 1990. Finding age with relative time:.

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Relative time
Relative Time:

  • Ages of events are placed in order of occurrence.

  • No exact date is identified.

    • Ex. WWI and WWII

    • I am the second child in my family.


Absolute time
Absolute Time:

  • identifies the exact date of an event.

    • Ex. 65 Million Years Ago

    • 1990


Finding age with relative time
Finding age with relative time:

  • The Law of Superposition - in a sequence of undisturbed sedimentary rocks, the oldest rocks will be at the bottom.


2. The law of cross-cutting relationships – anything that cuts across layers of rock is younger than the rocks that it has intruded into. This applies to faults and igneous intrusions.


3 the law of included fragments the fragments that make up a rock are older than the entire sample
3. The law of included fragments - the fragments that make up a rock are older than the entire sample.


  • The Law of Folds or Tilts: tilts in rocks are younger than the rocks themselves.

  • Original Horizontality- Rocks are usually deposited flat and level.

  • Cole’s Law-

    Thinly sliced cabbage.


Other guidelines for figuring out a sequence
Other Guidelines for figuring out a sequence:

  • Sedimentary rocks are usually formed under water.

  • Weathering and erosion usually happen above water (on dry land).



Time for a worksheet
Time for a worksheet was there first when the intrusion happened.

  • Sequence 1 & 2


Sequence 1 uplift erosion
Sequence 1: Uplift & Erosion was there first when the intrusion happened.

  • Limestone deposited

  • Sandstone deposited

  • Shale Deposited

  • Uplift

  • Erosion


Sequence 2 faulting
Sequence 2: Faulting was there first when the intrusion happened.

  • Limestone deposited

  • Sandstone deposited

  • Shale deposited

  • Faulting


Time for another worksheet
Time for another worksheet was there first when the intrusion happened.

  • Sequence 3 & 4


Sequence 3 folding
Sequence 3: Folding was there first when the intrusion happened.

  • Limestone deposited

  • Sandstone deposited

  • Shale deposited

  • Folding


By the way
By the way… was there first when the intrusion happened.

  • How can you tell if folding has gone so far as to flip the layers over?


Sequence 4 igneous intrusion
Sequence 4: Igneous Intrusion was there first when the intrusion happened.

  • Limestone deposited

  • Sandstone deposited

  • Shale deposited

  • Igneous Intrusion

    Note: contact metamorphism is the same event as the intrusion.


Formation of an unconformity
Formation of an unconformity was there first when the intrusion happened.


Layers are formed according to superposition. was there first when the intrusion happened.


Something happens to uplift the area was there first when the intrusion happened.

folding

faulting, etc.


Erosion wears away the uppermost layers was there first when the intrusion happened.


Area submerges and deposition begins again. was there first when the intrusion happened.

Here’s the

unconformity


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