Self-paced
P1
To study centuries-old earthquakes and the geologic faults that caused them, seismologists usually dig trenches along visible fault lines, looking for sediments that show evidence of having shifted. ███
Intro topic ·
Methods for studying causes of past earthquakes
Start by looking for buried sediments that shifted during a possible earthquake
Explain method ·
Use carbon 14 to back-date when material shifted (i.e., when possible earthquake occurred)
Carbon 14 is a radioactive form of carbon that decays (i.e., turns into a different form of carbon) at a known rate, so the amount of carbon 14 left in something can tell us how old that thing is
Application of method ·
Determine details of past earthquakes, predict future earthquakes
P2
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Intro new method ·
Lichenometry
Explain new method ·
Use lichen growth to back-date rockfalls in mountain ranges
Lichens begin growing on rocks after an earthquake causes rockfalls; because they grow at a known rate, the size of a lichen patch on a rock can tell us when that rock first fell
Application of new method ·
If many rockfalls occurred at the same time, that suggests an earthquake
Earthquake was strongest where the most number of rockfalls occurred
P3
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Support for lichenometry ·
over carbon 14 dating
Carbon 14 dating is less accurate because it can be hard to know how much carbon 14 the material started with (just knowing the rate of carbon 14 decay on its own can't tell us how old that material is)
Limitations of lichenometry ·
Limited time period, complications related to site selection
Passage Style
Single position
8.
Given the information in the ████████ ██ █████ ███ ██ ███ █████████ █████ ████████████ ██████ ██ ████ ███████████
a
identifying the number ██ █████ █ ██████████ █████ ███ ███████ ██ ███ ████ █████ █████
It’s not clear how lichenometry can help identify the number of times a river has flooded. Lichenometry measures the size of lichens growing on rock. If a river has flooded, it’s not clear how that impacts the lichens.
b
identifying the age ██ █ ██████████ ████████ ██ █ ██████ ████ █████ ████ █████████ ██ █████ ███
It’s not clear how lichenometry can help identify the age of a skeleton. The technique measures the size of lichens growing on rock.
c
identifying the age ██ ██ ███████ █████ ███ ██████████ █████████████ ██ ██████████ ███ ███ ███████ █████
It’s not clear how lichenometry can help identify the age of a beach that’s underwater. The technique measures the size of lichens growing on rock.
d
identifying the rate, ██ ██████████ ███ ████████ ██ █████ █ ███████ ███ ████ ████████ ██ █ ████████ ██████
This is the best answer, because we might be able to identify the rate a glacier has been moving/melting up a mountain valley by measuring lichen growth on the rock that is exposed when the glacier recedes. No other answer involves a measurement that we can make based on lichen growth on exposed rock.
e
identifying local trends ██ ██████ ████████ █████ ██ █ ██████████ ██████ ████ ███ ████ ████ █████████
It’s not clear how lichenometry can help identify trends in annual rainfall. The technique measures the size of lichens growing on rock. Does rainfall affect lichens? And how? We don’t know.