1. How does sea-floor spreading occur?

A. New materials are being added to the asthenosphere.
B. Earthquakes brake apart the ocean floor.
C. Sediments accumulate at the area of spreading.
D. Molten material beneath Earth's crust rises to the surface.*

thanks!

Seafloor spreading is a process that occurs at mid-ocean ridges, where new oceanic crust is formed through volcanic activity and then gradually moves away from the ridge. Seafloor spreading helps explain continental drift in the theory of plate tectonics.

Right.

soooooo, D?

The correct answer is D. Molten material beneath Earth's crust rises to the surface.

Sea-floor spreading is a geologic process that occurs at the mid-oceanic ridge system, where new oceanic crust is formed. This process is driven by the movement of molten material, known as magma, beneath Earth's crust.

Here's an explanation of how sea-floor spreading occurs:

1. Magma generation: In the Earth's mantle, which is the layer below the crust, there is a region known as the asthenosphere. The asthenosphere is partially molten, and convection currents within it cause the movement of magma.

2. Upwelling of magma: As the mantle material heats up and rises, it forms currents that carry the magma upwards towards the surface. These convection currents can be caused by the heat from the Earth's core.

3. Formation of mid-oceanic ridges: When the upwelling magma reaches the base of the oceanic crust, it creates pressure that fractures the crust. This allows the molten material to rise to the surface, forming a volcanic ridge known as a mid-oceanic ridge.

4. Spreading of oceanic crust: As the magma erupts onto the ocean floor, it cools and solidifies, creating new oceanic crust. The crust then moves away from the ridge on both sides, propelled by the continued upwelling of magma. This is called sea-floor spreading.

5. Subduction and recycling: As the oceanic crust spreads, it eventually reaches a trench, which is a deep depression on the ocean floor. At the trench, the older, denser oceanic crust is subducted, or forced beneath the lighter crust. This subduction process is part of the larger process of plate tectonics and helps to recycle the Earth's crust.

So, in summary, sea-floor spreading occurs as molten material from the mantle rises to the surface, creating new oceanic crust and causing the existing crust to move away from the mid-oceanic ridge.