U3L2–3: Geologic Change & Relative Dating
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What is uniformitarianism?
The theory that the same geological processes happening today operated in the past over long periods of time
What phrase summarizes uniformitarianism?
The present is the key to the past
What types of processes support uniformitarianism?
Erosion, deposition, volcanism, earthquakes, and plate movement
What is catastrophism?
The theory that Earths surface changes mainly through sudden violent events
How does catastrophism differ from uniformitarianism?
Catastrophism focuses on rapid events while uniformitarianism focuses on slow gradual change
What is the Law of Superposition?
In undisturbed rock layers the oldest layers are at the bottom and the youngest are at the top
When does the Law of Superposition apply?
Only when rock layers are undisturbed
What does undisturbed mean in geology?
Rock layers remain in their original horizontal position
What is relative dating?
Determining whether something is older or younger than something else
Does relative dating give an exact age?
No, it only compares ages
What is absolute dating?
Determining the exact numerical age of a rock or fossil
Why is absolute dating a distractor on this quiz?
The quiz focuses on relative dating, not numerical ages
What is an unconformity?
A gap in the rock record where layers are missing
What causes an unconformity?
Erosion or non deposition over time
What does an unconformity show about Earths history?
Time passed without rock layers forming
What is an intrusion?
Molten rock that squeezes into existing rock layers and cools
How old is an intrusion compared to surrounding layers?
It is younger than the layers it cuts through
What is a fault?
A break in Earths crust where movement occurs
How old is a fault compared to the rock layers it cuts?
The fault is younger than the layers
What does folding in rock layers indicate?
Rock layers were disturbed by tectonic forces
What does tilting of rock layers indicate?
Rock layers were moved from their original horizontal position
What do folding tilting and faulting all show?
The rock layers are disturbed
Why do disturbances matter in relative dating?
They can affect how the Law of Superposition is applied
What are trace fossils?
Fossils formed by the activity or movement of organisms