Question

The origin of submarine canyons is not well understood, but most likely __________.

(a) is tectonic, and represents down-folds of rock within the continental shelf
(b) is organic, resulting from the activities of burrowing organisms
(c) is glacial, the work of glaciers depositing rock debris on the shelf
(d) is erosional, started by streams during periods of sea level lowering

Answer 1

The most likely origin of submarine canyons is erosional, caused by streams during periods when sea levels were lower, which then became submerged as sea levels rose.

Step-by-step explanation:

The origin of submarine canyons is not completely understood, but they most likely are erosional, started by streams during periods of sea level lowering. During such periods, rivers and streams extend their courses, cutting into the continental shelf and starting to carve out canyons. Later, as sea levels rise again, these features become submerged, yet their erosional patterns remain. This aligns with observations of similar processes seen with canyons on land that have been shaped by water flow, such as undercutting from rivers leading to landslides, which eventually widen into valleys.

The idea that canyons are formed through tectonic activity also finds support in the creation of features like trenches in subduction zones. However, subduction primarily involves oceanic rather than continental plates and typically leads to the formation of trenches, not canyons. So, while tectonic activity plays a role in shaping the ocean floor, the erosional hypothesis is favored for the direct formation of submarine canyons.