Question

Ocean floor subducts under continents because:_________.

i. the ocean floor is made of mafic material and is therefore more dense than continental material. ii. the weight of the continents is so great that they push the ocean floor material downward. iii. the ocean floor is made of felsic minerals and is heavier than continental material. iv. the ocean floor has a lower density and therefore sinks more easily. v. both i and ii

Answer 1

Ocean floor subducts under continents mainly because it is composed of dense mafic material like basalt and gabbro, causing it to be denser than the lighter continental crust and sink into subduction zones during tectonic plate convergence.

Step-by-step explanation:

The ocean floor subducts under continents primarily because the ocean floor is made of mafic material and is therefore more dense than continental material. This mafic material, specifically basalt and gabbro, produces a higher density oceanic crust as compared to the continental crust, which is largely composed of less dense granite. When oceanic and continental plates converge, the denser oceanic plate is forced beneath the lighter continental plate into subduction zones, often marked by ocean trenches.

Additionally, it is not the weight of the continents that pushes the oceanic crust downward, as continental mass alone does not account for subduction. Both the composition and the resultant density of the oceanic crust are the primary factors driving subduction, along with the dynamics of plate tectonics powered by mantle convection.

Answer 2

i.

Step-by-step explanation:

the ocean floor is made of mafic material and is therefore more dense than continental material:

When an oceanic plate converges with a continental plate, the oceanic crust will always subduct under the continental crust; this is because oceanic crust is naturally denser.