Difficulty: Medium
Correct Answer: craton
Explanation:
Introduction / Context:
Continental interiors contain very old, stable cores made of ancient crystalline basement overlain in places by younger, relatively undeformed sedimentary cover. Distinguishing the terms shield, platform, basement, and craton is essential for structural geology and tectonics questions.
Given Data / Assumptions:
Concept / Approach:
A craton is the fundamental, mechanically stable portion of continental lithosphere. Where the basement is uncovered, it forms a shield; where the basement is covered by relatively undeformed sediments, that surface expression is termed a platform. Together, these expressions make up the craton. Therefore, “platform + basement” is most accurately named a craton, not a shield. A shield is a special case (exposed basement) and does not require an overlying platform.
Step-by-Step Solution:
Verification / Alternative check:
Geology texts consistently portray shields and platforms as components of cratons. Maps label Canadian Shield (exposed basement) and adjacent platforms as parts of the North American craton.
Why Other Options Are Wrong:
Common Pitfalls:
Using “shield” and “craton” interchangeably. A shield is a type-area within a craton; the craton includes both shield and platform regions.
Final Answer:
craton
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