5. When the sea floor spreads apart, volcanoes and ridges are formed
because -
a. sediments are deposited where the floor spreads, building ridges
b. as the plates pull apart, magma moves to the surface, building ridges
c. ocean water pushes down on the surrounding sea floor, pushing up ridges
d. underwater earthquakes lift the sea floor into long ridges

Seafloor spreading occurs at divergent plate boundaries.
As tectonic plates slowly move away from each other, heat from the mantle's convection currents makes the crust more plastic and less dense.
The less-dense material rises, often forming a mountain or elevated area of the seafloor.

What happens during the process of sea floor spreading?

Sea-floor spreading is what happens at the mid-oceanic ridge where a divergent boundary is causing two plates to move away from one another resulting in spreading of the sea floor.
As the plates move apart, new material wells up and cools onto the edge of the plates.

The phenomenon is known today as plate tectonics.
In locations where two plates move apart, at mid-ocean ridges, new seafloor is continually formed during seafloor spreading.

Features of the ocean floor include the continental shelf and slope, abyssal plain, trenches, seamounts, and the mid-ocean ridge.
The ocean floor is rich in resources.
Living things on the ocean floor are used for food or medicines.

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