Question

What must always precede a continent-continent collision?

A. Ocean and continent must converge.
B. Ocean and ocean must converge.
C. The poles must have recently switched.
D. A major earthquake must occur.
E. The Mid-Atlantic Ridge must be particularly active.

Answer 1

A continent-continent collision is always preceded by a continent-ocean convergence, where the oceanic plate is subducted beneath the continental plate. This process leads to a reduction in oceanic crust, setting the stage for the eventual collision between two continental masses.

Step-by-step explanation:

Before a continent-continent collision can occur, a necessary step involves a continent-ocean convergence. This is when an oceanic plate converges with a continental plate, leading to the oceanic plate being subducted beneath the continental plate. As a result of this subduction, the oceanic crust is pushed down into the mantle, where it is melted and recycled. This reduction in oceanic crust continues until two continental masses meet, resulting in a collision and subsequent mountain building.

Ophiolites, which are slices of oceanic crust and the underlying upper mantle that have been uplifted and exposed above sea level, are evidence of past ocean basins and are a signature of previous oceanic crust that existed between the two colliding continental tectonic plates.

Therefore, the correct answer to the question 'What must always precede a continent-continent collision?' is A. Ocean and continent must converge.