SME
Historical Geology · Problem type
Which principle dates it?
Use this for “A dike cuts a sill. Which principle says which is older?”
Sort
Which principle tells the order of events in each case?
Tap a card, then tap its group.
Ask what the rocks show: a stack, a tilt, a cut, a piece inside, or fossils in order.
Assumptions
•
These principles give a relative order, older or younger, never an age in years.
•
Each card names one relation seen in the rocks; one principle explains it best.
•
Faunal succession works because life changed over time, so the same fossils mark rock of the same age.
Topic check
See what you know: 5 questions on this topic
New questions each time. Pass to mark it complete.
Related lessons
Stratigraphy
Main lesson
Deposition rate between dated beds
Use this for “An ash bed is 252 Ma and a lava flow 50 m below it is 254.5 Ma. How fast did the beds pile up, and how old is a fossil bed 30 m up?”
Name the unconformity
Use this for “Flat sandstone lies on eroded granite. What kind of unconformity is it?”