Difficulty: Easy
Correct Answer: isostasy
Explanation:
Introduction / Context:
During the last glacial maximum, thick ice sheets depressed the lithosphere. After deglaciation, removal of the ice load triggered a slow, continuing rebound of the crust that changes relative sea level along affected coasts.
Given Data / Assumptions:
Concept / Approach:
Isostasy describes gravitational equilibrium between Earth’s lithosphere and asthenosphere. Post-glacial isostatic adjustment (glacio-isostatic rebound) raises formerly glaciated crust while surrounding forebulges may subside, altering relative sea level.
Step-by-Step Solution:
Identify load removal (melting ice) → reduced lithospheric depression.Viscous mantle flows back, pushing crust upward over millennia.Observed effect: raised shorelines, changing tidal datums, and relative sea-level trends.This is isostasy in action.
Verification / Alternative check:
Raised paleo-shorelines and GPS geodesy document uplift rates of several mm/year in Fennoscandia and parts of Canada.
Why Other Options Are Wrong:
Continental drift/plate tectonics — plate motions occur, but the described coastal changes are dominated by glacio-isostatic rebound.None of the above/orographic rebound — not the correct terminology.
Common Pitfalls:
Confusing eustatic (global) sea-level change with local relative sea-level change due to vertical land motion.
Final Answer:
isostasy
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