In oceanography, any oceanic trench that forms at a convergent plate boundary frequently experiences deep-focus earthquakes. Furthermore, any geological structure that frequently experiences deep-focus earthquakes must feature a subducting lithospheric plate. However, extensive geological surveys demonstrate that no oceanic trench in the Kyra Basin features a subducting lithospheric plate. Additionally, some geological structures that feature subducting lithospheric plates are also characterized by volcanic arc formation.
Which of the following must be true based on the information above?
- No oceanic trench in the Kyra Basin forms at a convergent plate boundary.Cevap
- BAny geological structure that features a subducting lithospheric plate forms at a convergent plate boundary.
- CIf an oceanic trench does not form at a convergent plate boundary, it does not frequently experience deep-focus earthquakes.
- DMost geological structures that feature a subducting lithospheric plate are characterized by volcanic arc formation.
- EThe oceanic trenches in the Kyra Basin do not experience any type of earthquake activity.
Cevap
No oceanic trench in the Kyra Basin forms at a convergent plate boundary.
The stimulus sets up a formal conditional chain: forming at a convergent plate boundary guarantees deep-focus earthquakes, which in turn guarantees the presence of a subducting lithospheric plate. We are then told that trenches in the Kyra Basin do NOT have a subducting lithospheric plate. Applying the contrapositive of our chain, if the necessary condition (subducting plate) is absent, the sufficient conditions that lead to it must also be absent. Thus, a Kyra Basin trench cannot experience deep-focus earthquakes, and consequently, it cannot form at a convergent plate boundary. The correct answer precisely states this guaranteed deduction.
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